1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4 <meta charset="utf-8"> 5 <meta name="viewport" content="width=device-width"> 6 <meta name="nodejs.org:node-version" content="v14.20.1"> 7 <title>Node-API | Node.js v14.20.1 Documentation</title> 8 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> 9 <link rel="stylesheet" href="assets/style.css"> 10 <link rel="stylesheet" href="assets/hljs.css"> 11 <link rel="canonical" href="https://nodejs.org/api/n-api.html"> 12 </head> 13 <body class="alt apidoc" id="api-section-n-api"> 14 <div id="content" class="clearfix"> 15 <div id="column2" class="interior"> 16 <div id="intro" class="interior"> 17 <a href="/" title="Go back to the home page"> 18 Node.js 19 </a> 20 </div> 21 <ul> 22 <li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 23 <li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 24 </ul> 25 <hr class="line"> 26 <ul> 27 <li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 28 <li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 29 <li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 30 <li><a href="addons.html" class="nav-addons">C++ addons</a></li> 31 <li><a href="n-api.html" class="nav-n-api active">C/C++ addons with Node-API</a></li> 32 <li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 33 <li><a href="child_process.html" class="nav-child_process">Child processes</a></li> 34 <li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 35 <li><a href="cli.html" class="nav-cli">Command-line options</a></li> 36 <li><a href="console.html" class="nav-console">Console</a></li> 37 <li><a href="corepack.html" class="nav-corepack">Corepack</a></li> 38 <li><a href="crypto.html" class="nav-crypto">Crypto</a></li> 39 <li><a href="debugger.html" class="nav-debugger">Debugger</a></li> 40 <li><a href="deprecations.html" 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87 </div> 88 89 <div id="column1" data-id="n-api" class="interior"> 90 <header> 91 <div class="header-container"> 92 <h1>Node.js v14.20.1 documentation</h1> 93 <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 94 <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 95 <path fill="none" d="M0 0h24v24H0z" /> 96 <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 97 <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 98 </svg> 99 <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 100 <path d="M0 0h24v24H0z" fill="none" /> 101 <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 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href="https://nodejs.org/docs/latest-v15.x/api/n-api.html">15.x</a></li> 123 <li><a href="https://nodejs.org/docs/latest-v14.x/api/n-api.html">14.x <b>LTS</b></a></li> 124 <li><a href="https://nodejs.org/docs/latest-v13.x/api/n-api.html">13.x</a></li> 125 <li><a href="https://nodejs.org/docs/latest-v12.x/api/n-api.html">12.x <b>LTS</b></a></li> 126 <li><a href="https://nodejs.org/docs/latest-v11.x/api/n-api.html">11.x</a></li> 127 <li><a href="https://nodejs.org/docs/latest-v10.x/api/n-api.html">10.x</a></li> 128 <li><a href="https://nodejs.org/docs/latest-v9.x/api/n-api.html">9.x</a></li> 129 <li><a href="https://nodejs.org/docs/latest-v8.x/api/n-api.html">8.x</a></li></ol> 130 </li> 131 132 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/n-api.md">Edit on GitHub</a></li> 133 </ul> 134 </div> 135 <hr> 136 </header> 137 138 <details id="toc" open><summary>Table of contents</summary><ul> 139 <li><span class="stability_2"><a href="#n_api_node_api">Node-API</a></span> 140 <ul> 141 <li><a href="#n_api_implications_of_abi_stability">Implications of ABI stability</a></li> 142 <li><a href="#n_api_building">Building</a> 143 <ul> 144 <li><a href="#n_api_build_tools">Build tools</a> 145 <ul> 146 <li><a href="#n_api_node_gyp">node-gyp</a></li> 147 <li><a href="#n_api_cmake_js">CMake.js</a></li> 148 </ul> 149 </li> 150 <li><a href="#n_api_uploading_precompiled_binaries">Uploading precompiled binaries</a> 151 <ul> 152 <li><a href="#n_api_node_pre_gyp">node-pre-gyp</a></li> 153 <li><a href="#n_api_prebuild">prebuild</a></li> 154 <li><a href="#n_api_prebuildify">prebuildify</a></li> 155 </ul> 156 </li> 157 </ul> 158 </li> 159 <li><a href="#n_api_usage">Usage</a></li> 160 <li><a href="#n_api_node_api_version_matrix">Node-API version matrix</a></li> 161 <li><a href="#n_api_environment_life_cycle_apis">Environment life cycle APIs</a> 162 <ul> 163 <li><a href="#n_api_napi_set_instance_data">napi_set_instance_data</a></li> 164 <li><a href="#n_api_napi_get_instance_data">napi_get_instance_data</a></li> 165 </ul> 166 </li> 167 <li><a href="#n_api_basic_node_api_data_types">Basic Node-API data types</a> 168 <ul> 169 <li><a href="#n_api_napi_status">napi_status</a></li> 170 <li><a href="#n_api_napi_extended_error_info">napi_extended_error_info</a></li> 171 <li><a href="#n_api_napi_env">napi_env</a></li> 172 <li><a href="#n_api_napi_value">napi_value</a></li> 173 <li><a href="#n_api_napi_threadsafe_function">napi_threadsafe_function</a></li> 174 <li><a href="#n_api_napi_threadsafe_function_release_mode">napi_threadsafe_function_release_mode</a></li> 175 <li><a href="#n_api_napi_threadsafe_function_call_mode">napi_threadsafe_function_call_mode</a></li> 176 <li><a href="#n_api_node_api_memory_management_types">Node-API memory management types</a> 177 <ul> 178 <li><a href="#n_api_napi_handle_scope">napi_handle_scope</a></li> 179 <li><a href="#n_api_napi_escapable_handle_scope">napi_escapable_handle_scope</a></li> 180 <li><a href="#n_api_napi_ref">napi_ref</a></li> 181 <li><a href="#n_api_napi_type_tag">napi_type_tag</a></li> 182 <li><a href="#n_api_napi_async_cleanup_hook_handle">napi_async_cleanup_hook_handle</a></li> 183 </ul> 184 </li> 185 <li><a href="#n_api_node_api_callback_types">Node-API callback types</a> 186 <ul> 187 <li><a href="#n_api_napi_callback_info">napi_callback_info</a></li> 188 <li><a href="#n_api_napi_callback">napi_callback</a></li> 189 <li><a href="#n_api_napi_finalize">napi_finalize</a></li> 190 <li><a href="#n_api_napi_async_execute_callback">napi_async_execute_callback</a></li> 191 <li><a href="#n_api_napi_async_complete_callback">napi_async_complete_callback</a></li> 192 <li><a href="#n_api_napi_threadsafe_function_call_js">napi_threadsafe_function_call_js</a></li> 193 <li><a href="#n_api_napi_async_cleanup_hook">napi_async_cleanup_hook</a></li> 194 </ul> 195 </li> 196 </ul> 197 </li> 198 <li><a href="#n_api_error_handling">Error handling</a> 199 <ul> 200 <li><a href="#n_api_return_values">Return values</a> 201 <ul> 202 <li><a href="#n_api_napi_get_last_error_info">napi_get_last_error_info</a></li> 203 </ul> 204 </li> 205 <li><a href="#n_api_exceptions">Exceptions</a> 206 <ul> 207 <li><a href="#n_api_napi_throw">napi_throw</a></li> 208 <li><a href="#n_api_napi_throw_error">napi_throw_error</a></li> 209 <li><a href="#n_api_napi_throw_type_error">napi_throw_type_error</a></li> 210 <li><a href="#n_api_napi_throw_range_error">napi_throw_range_error</a></li> 211 <li><a href="#n_api_napi_is_error">napi_is_error</a></li> 212 <li><a href="#n_api_napi_create_error">napi_create_error</a></li> 213 <li><a href="#n_api_napi_create_type_error">napi_create_type_error</a></li> 214 <li><a href="#n_api_napi_create_range_error">napi_create_range_error</a></li> 215 <li><a href="#n_api_napi_get_and_clear_last_exception">napi_get_and_clear_last_exception</a></li> 216 <li><a href="#n_api_napi_is_exception_pending">napi_is_exception_pending</a></li> 217 <li><a href="#n_api_napi_fatal_exception">napi_fatal_exception</a></li> 218 </ul> 219 </li> 220 <li><a href="#n_api_fatal_errors">Fatal errors</a> 221 <ul> 222 <li><a href="#n_api_napi_fatal_error">napi_fatal_error</a></li> 223 </ul> 224 </li> 225 </ul> 226 </li> 227 <li><a href="#n_api_object_lifetime_management">Object lifetime management</a> 228 <ul> 229 <li><a href="#n_api_making_handle_lifespan_shorter_than_that_of_the_native_method">Making handle lifespan shorter than that of the native method</a> 230 <ul> 231 <li><a href="#n_api_napi_open_handle_scope">napi_open_handle_scope</a></li> 232 <li><a href="#n_api_napi_close_handle_scope">napi_close_handle_scope</a></li> 233 <li><a href="#n_api_napi_open_escapable_handle_scope">napi_open_escapable_handle_scope</a></li> 234 <li><a href="#n_api_napi_close_escapable_handle_scope">napi_close_escapable_handle_scope</a></li> 235 <li><a href="#n_api_napi_escape_handle">napi_escape_handle</a></li> 236 </ul> 237 </li> 238 <li><a href="#n_api_references_to_objects_with_a_lifespan_longer_than_that_of_the_native_method">References to objects with a lifespan longer than that of the native method</a> 239 <ul> 240 <li><a href="#n_api_napi_create_reference">napi_create_reference</a></li> 241 <li><a href="#n_api_napi_delete_reference">napi_delete_reference</a></li> 242 <li><a href="#n_api_napi_reference_ref">napi_reference_ref</a></li> 243 <li><a href="#n_api_napi_reference_unref">napi_reference_unref</a></li> 244 <li><a href="#n_api_napi_get_reference_value">napi_get_reference_value</a></li> 245 </ul> 246 </li> 247 <li><a href="#n_api_cleanup_on_exit_of_the_current_node_js_instance">Cleanup on exit of the current Node.js instance</a> 248 <ul> 249 <li><a href="#n_api_napi_add_env_cleanup_hook">napi_add_env_cleanup_hook</a></li> 250 <li><a href="#n_api_napi_remove_env_cleanup_hook">napi_remove_env_cleanup_hook</a></li> 251 <li><a href="#n_api_napi_add_async_cleanup_hook">napi_add_async_cleanup_hook</a></li> 252 <li><a href="#n_api_napi_remove_async_cleanup_hook">napi_remove_async_cleanup_hook</a></li> 253 </ul> 254 </li> 255 </ul> 256 </li> 257 <li><a href="#n_api_module_registration">Module registration</a></li> 258 <li><a href="#n_api_working_with_javascript_values">Working with JavaScript values</a> 259 <ul> 260 <li><a href="#n_api_enum_types">Enum types</a> 261 <ul> 262 <li><a href="#n_api_napi_key_collection_mode">napi_key_collection_mode</a></li> 263 <li><a href="#n_api_napi_key_filter">napi_key_filter</a></li> 264 <li><a href="#n_api_napi_key_conversion">napi_key_conversion</a></li> 265 <li><a href="#n_api_napi_valuetype">napi_valuetype</a></li> 266 <li><a href="#n_api_napi_typedarray_type">napi_typedarray_type</a></li> 267 </ul> 268 </li> 269 <li><a href="#n_api_object_creation_functions">Object creation functions</a> 270 <ul> 271 <li><a href="#n_api_napi_create_array">napi_create_array</a></li> 272 <li><a href="#n_api_napi_create_array_with_length">napi_create_array_with_length</a></li> 273 <li><a href="#n_api_napi_create_arraybuffer">napi_create_arraybuffer</a></li> 274 <li><a href="#n_api_napi_create_buffer">napi_create_buffer</a></li> 275 <li><a href="#n_api_napi_create_buffer_copy">napi_create_buffer_copy</a></li> 276 <li><a href="#n_api_napi_create_date">napi_create_date</a></li> 277 <li><a href="#n_api_napi_create_external">napi_create_external</a></li> 278 <li><a href="#n_api_napi_create_external_arraybuffer">napi_create_external_arraybuffer</a></li> 279 <li><a href="#n_api_napi_create_external_buffer">napi_create_external_buffer</a></li> 280 <li><a href="#n_api_napi_create_object">napi_create_object</a></li> 281 <li><a href="#n_api_napi_create_symbol">napi_create_symbol</a></li> 282 <li><a href="#n_api_napi_create_typedarray">napi_create_typedarray</a></li> 283 <li><a href="#n_api_napi_create_dataview">napi_create_dataview</a></li> 284 </ul> 285 </li> 286 <li><a href="#n_api_functions_to_convert_from_c_types_to_node_api">Functions to convert from C types to Node-API</a> 287 <ul> 288 <li><a href="#n_api_napi_create_int32">napi_create_int32</a></li> 289 <li><a href="#n_api_napi_create_uint32">napi_create_uint32</a></li> 290 <li><a href="#n_api_napi_create_int64">napi_create_int64</a></li> 291 <li><a href="#n_api_napi_create_double">napi_create_double</a></li> 292 <li><a href="#n_api_napi_create_bigint_int64">napi_create_bigint_int64</a></li> 293 <li><a href="#n_api_napi_create_bigint_uint64">napi_create_bigint_uint64</a></li> 294 <li><a href="#n_api_napi_create_bigint_words">napi_create_bigint_words</a></li> 295 <li><a href="#n_api_napi_create_string_latin1">napi_create_string_latin1</a></li> 296 <li><a href="#n_api_napi_create_string_utf16">napi_create_string_utf16</a></li> 297 <li><a href="#n_api_napi_create_string_utf8">napi_create_string_utf8</a></li> 298 </ul> 299 </li> 300 <li><a href="#n_api_functions_to_convert_from_node_api_to_c_types">Functions to convert from Node-API to C types</a> 301 <ul> 302 <li><a href="#n_api_napi_get_array_length">napi_get_array_length</a></li> 303 <li><a href="#n_api_napi_get_arraybuffer_info">napi_get_arraybuffer_info</a></li> 304 <li><a href="#n_api_napi_get_buffer_info">napi_get_buffer_info</a></li> 305 <li><a href="#n_api_napi_get_prototype">napi_get_prototype</a></li> 306 <li><a href="#n_api_napi_get_typedarray_info">napi_get_typedarray_info</a></li> 307 <li><a href="#n_api_napi_get_dataview_info">napi_get_dataview_info</a></li> 308 <li><a href="#n_api_napi_get_date_value">napi_get_date_value</a></li> 309 <li><a href="#n_api_napi_get_value_bool">napi_get_value_bool</a></li> 310 <li><a href="#n_api_napi_get_value_double">napi_get_value_double</a></li> 311 <li><a href="#n_api_napi_get_value_bigint_int64">napi_get_value_bigint_int64</a></li> 312 <li><a href="#n_api_napi_get_value_bigint_uint64">napi_get_value_bigint_uint64</a></li> 313 <li><a href="#n_api_napi_get_value_bigint_words">napi_get_value_bigint_words</a></li> 314 <li><a href="#n_api_napi_get_value_external">napi_get_value_external</a></li> 315 <li><a href="#n_api_napi_get_value_int32">napi_get_value_int32</a></li> 316 <li><a href="#n_api_napi_get_value_int64">napi_get_value_int64</a></li> 317 <li><a href="#n_api_napi_get_value_string_latin1">napi_get_value_string_latin1</a></li> 318 <li><a href="#n_api_napi_get_value_string_utf8">napi_get_value_string_utf8</a></li> 319 <li><a href="#n_api_napi_get_value_string_utf16">napi_get_value_string_utf16</a></li> 320 <li><a href="#n_api_napi_get_value_uint32">napi_get_value_uint32</a></li> 321 </ul> 322 </li> 323 <li><a href="#n_api_functions_to_get_global_instances">Functions to get global instances</a> 324 <ul> 325 <li><a href="#n_api_napi_get_boolean">napi_get_boolean</a></li> 326 <li><a href="#n_api_napi_get_global">napi_get_global</a></li> 327 <li><a href="#n_api_napi_get_null">napi_get_null</a></li> 328 <li><a href="#n_api_napi_get_undefined">napi_get_undefined</a></li> 329 </ul> 330 </li> 331 </ul> 332 </li> 333 <li><a href="#n_api_working_with_javascript_values_and_abstract_operations">Working with JavaScript values and abstract operations</a> 334 <ul> 335 <li><a href="#n_api_napi_coerce_to_bool">napi_coerce_to_bool</a></li> 336 <li><a href="#n_api_napi_coerce_to_number">napi_coerce_to_number</a></li> 337 <li><a href="#n_api_napi_coerce_to_object">napi_coerce_to_object</a></li> 338 <li><a href="#n_api_napi_coerce_to_string">napi_coerce_to_string</a></li> 339 <li><a href="#n_api_napi_typeof">napi_typeof</a></li> 340 <li><a href="#n_api_napi_instanceof">napi_instanceof</a></li> 341 <li><a href="#n_api_napi_is_array">napi_is_array</a></li> 342 <li><a href="#n_api_napi_is_arraybuffer">napi_is_arraybuffer</a></li> 343 <li><a href="#n_api_napi_is_buffer">napi_is_buffer</a></li> 344 <li><a href="#n_api_napi_is_date">napi_is_date</a></li> 345 <li><a href="#n_api_napi_is_error_1">napi_is_error</a></li> 346 <li><a href="#n_api_napi_is_typedarray">napi_is_typedarray</a></li> 347 <li><a href="#n_api_napi_is_dataview">napi_is_dataview</a></li> 348 <li><a href="#n_api_napi_strict_equals">napi_strict_equals</a></li> 349 <li><a href="#n_api_napi_detach_arraybuffer">napi_detach_arraybuffer</a></li> 350 <li><a href="#n_api_napi_is_detached_arraybuffer">napi_is_detached_arraybuffer</a></li> 351 </ul> 352 </li> 353 <li><a href="#n_api_working_with_javascript_properties">Working with JavaScript properties</a> 354 <ul> 355 <li><a href="#n_api_structures">Structures</a> 356 <ul> 357 <li><a href="#n_api_napi_property_attributes">napi_property_attributes</a></li> 358 <li><a href="#n_api_napi_property_descriptor">napi_property_descriptor</a></li> 359 </ul> 360 </li> 361 <li><a href="#n_api_functions">Functions</a> 362 <ul> 363 <li><a href="#n_api_napi_get_property_names">napi_get_property_names</a></li> 364 <li><a href="#n_api_napi_get_all_property_names">napi_get_all_property_names</a></li> 365 <li><a href="#n_api_napi_set_property">napi_set_property</a></li> 366 <li><a href="#n_api_napi_get_property">napi_get_property</a></li> 367 <li><a href="#n_api_napi_has_property">napi_has_property</a></li> 368 <li><a href="#n_api_napi_delete_property">napi_delete_property</a></li> 369 <li><a href="#n_api_napi_has_own_property">napi_has_own_property</a></li> 370 <li><a href="#n_api_napi_set_named_property">napi_set_named_property</a></li> 371 <li><a href="#n_api_napi_get_named_property">napi_get_named_property</a></li> 372 <li><a href="#n_api_napi_has_named_property">napi_has_named_property</a></li> 373 <li><a href="#n_api_napi_set_element">napi_set_element</a></li> 374 <li><a href="#n_api_napi_get_element">napi_get_element</a></li> 375 <li><a href="#n_api_napi_has_element">napi_has_element</a></li> 376 <li><a href="#n_api_napi_delete_element">napi_delete_element</a></li> 377 <li><a href="#n_api_napi_define_properties">napi_define_properties</a></li> 378 <li><a href="#n_api_napi_object_freeze">napi_object_freeze</a></li> 379 <li><a href="#n_api_napi_object_seal">napi_object_seal</a></li> 380 </ul> 381 </li> 382 </ul> 383 </li> 384 <li><a href="#n_api_working_with_javascript_functions">Working with JavaScript functions</a> 385 <ul> 386 <li><a href="#n_api_napi_call_function">napi_call_function</a></li> 387 <li><a href="#n_api_napi_create_function">napi_create_function</a></li> 388 <li><a href="#n_api_napi_get_cb_info">napi_get_cb_info</a></li> 389 <li><a href="#n_api_napi_get_new_target">napi_get_new_target</a></li> 390 <li><a href="#n_api_napi_new_instance">napi_new_instance</a></li> 391 </ul> 392 </li> 393 <li><a href="#n_api_object_wrap">Object wrap</a> 394 <ul> 395 <li><a href="#n_api_napi_define_class">napi_define_class</a></li> 396 <li><a href="#n_api_napi_wrap">napi_wrap</a></li> 397 <li><a href="#n_api_napi_unwrap">napi_unwrap</a></li> 398 <li><a href="#n_api_napi_remove_wrap">napi_remove_wrap</a></li> 399 <li><a href="#n_api_napi_type_tag_object">napi_type_tag_object</a></li> 400 <li><a href="#n_api_napi_check_object_type_tag">napi_check_object_type_tag</a></li> 401 <li><a href="#n_api_napi_add_finalizer">napi_add_finalizer</a></li> 402 </ul> 403 </li> 404 <li><a href="#n_api_simple_asynchronous_operations">Simple asynchronous operations</a> 405 <ul> 406 <li><a href="#n_api_napi_create_async_work">napi_create_async_work</a></li> 407 <li><a href="#n_api_napi_delete_async_work">napi_delete_async_work</a></li> 408 <li><a href="#n_api_napi_queue_async_work">napi_queue_async_work</a></li> 409 <li><a href="#n_api_napi_cancel_async_work">napi_cancel_async_work</a></li> 410 </ul> 411 </li> 412 <li><a href="#n_api_custom_asynchronous_operations">Custom asynchronous operations</a> 413 <ul> 414 <li><a href="#n_api_napi_async_init">napi_async_init</a></li> 415 <li><a href="#n_api_napi_async_destroy">napi_async_destroy</a></li> 416 <li><a href="#n_api_napi_make_callback">napi_make_callback</a></li> 417 <li><a href="#n_api_napi_open_callback_scope">napi_open_callback_scope</a></li> 418 <li><a href="#n_api_napi_close_callback_scope">napi_close_callback_scope</a></li> 419 </ul> 420 </li> 421 <li><a href="#n_api_version_management">Version management</a> 422 <ul> 423 <li><a href="#n_api_napi_get_node_version">napi_get_node_version</a></li> 424 <li><a href="#n_api_napi_get_version">napi_get_version</a></li> 425 </ul> 426 </li> 427 <li><a href="#n_api_memory_management">Memory management</a> 428 <ul> 429 <li><a href="#n_api_napi_adjust_external_memory">napi_adjust_external_memory</a></li> 430 </ul> 431 </li> 432 <li><a href="#n_api_promises">Promises</a> 433 <ul> 434 <li><a href="#n_api_napi_create_promise">napi_create_promise</a></li> 435 <li><a href="#n_api_napi_resolve_deferred">napi_resolve_deferred</a></li> 436 <li><a href="#n_api_napi_reject_deferred">napi_reject_deferred</a></li> 437 <li><a href="#n_api_napi_is_promise">napi_is_promise</a></li> 438 </ul> 439 </li> 440 <li><a href="#n_api_script_execution">Script execution</a> 441 <ul> 442 <li><a href="#n_api_napi_run_script">napi_run_script</a></li> 443 </ul> 444 </li> 445 <li><a href="#n_api_libuv_event_loop">libuv event loop</a> 446 <ul> 447 <li><a href="#n_api_napi_get_uv_event_loop">napi_get_uv_event_loop</a></li> 448 </ul> 449 </li> 450 <li><a href="#n_api_asynchronous_thread_safe_function_calls">Asynchronous thread-safe function calls</a> 451 <ul> 452 <li><a href="#n_api_calling_a_thread_safe_function">Calling a thread-safe function</a></li> 453 <li><a href="#n_api_reference_counting_of_thread_safe_functions">Reference counting of thread-safe functions</a></li> 454 <li><a href="#n_api_deciding_whether_to_keep_the_process_running">Deciding whether to keep the process running</a></li> 455 <li><a href="#n_api_napi_create_threadsafe_function">napi_create_threadsafe_function</a></li> 456 <li><a href="#n_api_napi_get_threadsafe_function_context">napi_get_threadsafe_function_context</a></li> 457 <li><a href="#n_api_napi_call_threadsafe_function">napi_call_threadsafe_function</a></li> 458 <li><a href="#n_api_napi_acquire_threadsafe_function">napi_acquire_threadsafe_function</a></li> 459 <li><a href="#n_api_napi_release_threadsafe_function">napi_release_threadsafe_function</a></li> 460 <li><a href="#n_api_napi_ref_threadsafe_function">napi_ref_threadsafe_function</a></li> 461 <li><a href="#n_api_napi_unref_threadsafe_function">napi_unref_threadsafe_function</a></li> 462 </ul> 463 </li> 464 <li><a href="#n_api_miscellaneous_utilities">Miscellaneous utilities</a></li> 465 <li><span class="stability_1"><a href="#n_api_node_api_get_module_file_name">node_api_get_module_file_name</a></span></li> 466 </ul> 467 </li> 468 </ul></details> 469 470 <div id="apicontent"> 471 <h2>Node-API<span><a class="mark" href="#n_api_node_api" id="n_api_node_api">#</a></span></h2> 472 473 474 <p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 475 <p>Node-API (formerly N-API) is an API for building native Addons. It is 476 independent from the underlying JavaScript runtime (for example, V8) and is 477 maintained as part of Node.js itself. This API will be Application Binary 478 Interface (ABI) stable across versions of Node.js. It is intended to insulate 479 addons from changes in the underlying JavaScript engine and allow modules 480 compiled for one major version to run on later major versions of Node.js without 481 recompilation. The <a href="https://nodejs.org/en/docs/guides/abi-stability/">ABI Stability</a> guide provides a more in-depth explanation.</p> 482 <p>Addons are built/packaged with the same approach/tools outlined in the section 483 titled <a href="addons.html">C++ Addons</a>. The only difference is the set of APIs that are used by 484 the native code. Instead of using the V8 or <a href="https://github.com/nodejs/nan">Native Abstractions for Node.js</a> 485 APIs, the functions available in Node-API are used.</p> 486 <p>APIs exposed by Node-API are generally used to create and manipulate 487 JavaScript values. Concepts and operations generally map to ideas specified 488 in the ECMA-262 Language Specification. The APIs have the following 489 properties:</p> 490 <ul> 491 <li>All Node-API calls return a status code of type <code>napi_status</code>. This 492 status indicates whether the API call succeeded or failed.</li> 493 <li>The API's return value is passed via an out parameter.</li> 494 <li>All JavaScript values are abstracted behind an opaque type named 495 <code>napi_value</code>.</li> 496 <li>In case of an error status code, additional information can be obtained 497 using <code>napi_get_last_error_info</code>. More information can be found in the error 498 handling section <a href="#n_api_error_handling">Error handling</a>.</li> 499 </ul> 500 <p>Node-API is a C API that ensures ABI stability across Node.js versions 501 and different compiler levels. A C++ API can be easier to use. 502 To support using C++, the project maintains a 503 C++ wrapper module called <a href="https://github.com/nodejs/node-addon-api"><code>node-addon-api</code></a>. 504 This wrapper provides an inlineable C++ API. Binaries built 505 with <code>node-addon-api</code> will depend on the symbols for the Node-API C-based 506 functions exported by Node.js. <code>node-addon-api</code> is a more 507 efficient way to write code that calls Node-API. Take, for example, the 508 following <code>node-addon-api</code> code. The first section shows the 509 <code>node-addon-api</code> code and the second section shows what actually gets 510 used in the addon.</p> 511 <pre><code class="language-cpp">Object obj = Object::<span class="hljs-built_in">New</span>(env); 512 obj[<span class="hljs-string">"foo"</span>] = String::<span class="hljs-built_in">New</span>(env, <span class="hljs-string">"bar"</span>);</code></pre> 513 <pre><code class="language-cpp">napi_status status; 514 napi_value object, string; 515 status = <span class="hljs-built_in">napi_create_object</span>(env, &object); 516 <span class="hljs-keyword">if</span> (status != napi_ok) { 517 <span class="hljs-built_in">napi_throw_error</span>(env, ...); 518 <span class="hljs-keyword">return</span>; 519 } 520 521 status = <span class="hljs-built_in">napi_create_string_utf8</span>(env, <span class="hljs-string">"bar"</span>, NAPI_AUTO_LENGTH, &string); 522 <span class="hljs-keyword">if</span> (status != napi_ok) { 523 <span class="hljs-built_in">napi_throw_error</span>(env, ...); 524 <span class="hljs-keyword">return</span>; 525 } 526 527 status = <span class="hljs-built_in">napi_set_named_property</span>(env, object, <span class="hljs-string">"foo"</span>, string); 528 <span class="hljs-keyword">if</span> (status != napi_ok) { 529 <span class="hljs-built_in">napi_throw_error</span>(env, ...); 530 <span class="hljs-keyword">return</span>; 531 }</code></pre> 532 <p>The end result is that the addon only uses the exported C APIs. As a result, 533 it still gets the benefits of the ABI stability provided by the C API.</p> 534 <p>When using <code>node-addon-api</code> instead of the C APIs, start with the API <a href="https://github.com/nodejs/node-addon-api#api-documentation">docs</a> 535 for <code>node-addon-api</code>.</p> 536 <p>The <a href="https://nodejs.github.io/node-addon-examples/">Node-API Resource</a> offers 537 an excellent orientation and tips for developers just getting started with 538 Node-API and <code>node-addon-api</code>.</p> 539 <section><h3>Implications of ABI stability<span><a class="mark" href="#n_api_implications_of_abi_stability" id="n_api_implications_of_abi_stability">#</a></span></h3> 540 <p>Although Node-API provides an ABI stability guarantee, other parts of Node.js do 541 not, and any external libraries used from the addon may not. In particular, 542 none of the following APIs provide an ABI stability guarantee across major 543 versions:</p> 544 <ul> 545 <li> 546 <p>the Node.js C++ APIs available via any of</p> 547 <pre><code class="language-cpp"><span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node.h></span></span> 548 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_buffer.h></span></span> 549 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_version.h></span></span> 550 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_object_wrap.h></span></span></code></pre> 551 </li> 552 <li> 553 <p>the libuv APIs which are also included with Node.js and available via</p> 554 <pre><code class="language-cpp"><span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><uv.h></span></span></code></pre> 555 </li> 556 <li> 557 <p>the V8 API available via</p> 558 <pre><code class="language-cpp"><span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><v8.h></span></span></code></pre> 559 </li> 560 </ul> 561 <p>Thus, for an addon to remain ABI-compatible across Node.js major versions, it 562 must use Node-API exclusively by restricting itself to using</p> 563 <pre><code class="language-c"><span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span></code></pre> 564 <p>and by checking, for all external libraries that it uses, that the external 565 library makes ABI stability guarantees similar to Node-API.</p> 566 </section><section><h3>Building<span><a class="mark" href="#n_api_building" id="n_api_building">#</a></span></h3> 567 <p>Unlike modules written in JavaScript, developing and deploying Node.js 568 native addons using Node-API requires an additional set of tools. Besides the 569 basic tools required to develop for Node.js, the native addon developer 570 requires a toolchain that can compile C and C++ code into a binary. In 571 addition, depending upon how the native addon is deployed, the <em>user</em> of 572 the native addon will also need to have a C/C++ toolchain installed.</p> 573 <p>For Linux developers, the necessary C/C++ toolchain packages are readily 574 available. <a href="https://gcc.gnu.org">GCC</a> is widely used in the Node.js community to build and 575 test across a variety of platforms. For many developers, the <a href="https://llvm.org">LLVM</a> 576 compiler infrastructure is also a good choice.</p> 577 <p>For Mac developers, <a href="https://developer.apple.com/xcode/">Xcode</a> offers all the required compiler tools. 578 However, it is not necessary to install the entire Xcode IDE. The following 579 command installs the necessary toolchain:</p> 580 <pre><code class="language-bash">xcode-select --install</code></pre> 581 <p>For Windows developers, <a href="https://visualstudio.microsoft.com">Visual Studio</a> offers all the required compiler 582 tools. However, it is not necessary to install the entire Visual Studio 583 IDE. The following command installs the necessary toolchain:</p> 584 <pre><code class="language-bash">npm install --global windows-build-tools</code></pre> 585 <p>The sections below describe the additional tools available for developing 586 and deploying Node.js native addons.</p> 587 <h4>Build tools<span><a class="mark" href="#n_api_build_tools" id="n_api_build_tools">#</a></span></h4> 588 <p>Both the tools listed here require that <em>users</em> of the native 589 addon have a C/C++ toolchain installed in order to successfully install 590 the native addon.</p> 591 <h5>node-gyp<span><a class="mark" href="#n_api_node_gyp" id="n_api_node_gyp">#</a></span></h5> 592 <p><a href="https://github.com/nodejs/node-gyp">node-gyp</a> is a build system based on the <a href="https://github.com/nodejs/gyp-next">gyp-next</a> fork of 593 Google's <a href="https://gyp.gsrc.io">GYP</a> tool and comes bundled with npm. GYP, and therefore node-gyp, 594 requires that Python be installed.</p> 595 <p>Historically, node-gyp has been the tool of choice for building native 596 addons. It has widespread adoption and documentation. However, some 597 developers have run into limitations in node-gyp.</p> 598 <h5>CMake.js<span><a class="mark" href="#n_api_cmake_js" id="n_api_cmake_js">#</a></span></h5> 599 <p><a href="https://github.com/cmake-js/cmake-js">CMake.js</a> is an alternative build system based on <a href="https://cmake.org">CMake</a>.</p> 600 <p>CMake.js is a good choice for projects that already use CMake or for 601 developers affected by limitations in node-gyp.</p> 602 <h4>Uploading precompiled binaries<span><a class="mark" href="#n_api_uploading_precompiled_binaries" id="n_api_uploading_precompiled_binaries">#</a></span></h4> 603 <p>The three tools listed here permit native addon developers and maintainers 604 to create and upload binaries to public or private servers. These tools are 605 typically integrated with CI/CD build systems like <a href="https://travis-ci.org">Travis CI</a> and 606 <a href="https://www.appveyor.com">AppVeyor</a> to build and upload binaries for a variety of platforms and 607 architectures. These binaries are then available for download by users who 608 do not need to have a C/C++ toolchain installed.</p> 609 <h5>node-pre-gyp<span><a class="mark" href="#n_api_node_pre_gyp" id="n_api_node_pre_gyp">#</a></span></h5> 610 <p><a href="https://github.com/mapbox/node-pre-gyp">node-pre-gyp</a> is a tool based on node-gyp that adds the ability to 611 upload binaries to a server of the developer's choice. node-pre-gyp has 612 particularly good support for uploading binaries to Amazon S3.</p> 613 <h5>prebuild<span><a class="mark" href="#n_api_prebuild" id="n_api_prebuild">#</a></span></h5> 614 <p><a href="https://github.com/prebuild/prebuild">prebuild</a> is a tool that supports builds using either node-gyp or 615 CMake.js. Unlike node-pre-gyp which supports a variety of servers, prebuild 616 uploads binaries only to <a href="https://help.github.com/en/github/administering-a-repository/about-releases">GitHub releases</a>. prebuild is a good choice for 617 GitHub projects using CMake.js.</p> 618 <h5>prebuildify<span><a class="mark" href="#n_api_prebuildify" id="n_api_prebuildify">#</a></span></h5> 619 <p><a href="https://github.com/prebuild/prebuildify">prebuildify</a> is a tool based on node-gyp. The advantage of prebuildify is 620 that the built binaries are bundled with the native module when it's 621 uploaded to npm. The binaries are downloaded from npm and are immediately 622 available to the module user when the native module is installed.</p> 623 </section><section><h3>Usage<span><a class="mark" href="#n_api_usage" id="n_api_usage">#</a></span></h3> 624 <p>In order to use the Node-API functions, include the file <a href="https://github.com/nodejs/node/blob/HEAD/src/node_api.h"><code>node_api.h</code></a> which 625 is located in the src directory in the node development tree:</p> 626 <pre><code class="language-c"><span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span></code></pre> 627 <p>This will opt into the default <code>NAPI_VERSION</code> for the given release of Node.js. 628 In order to ensure compatibility with specific versions of Node-API, the version 629 can be specified explicitly when including the header:</p> 630 <pre><code class="language-c"><span class="hljs-meta">#<span class="hljs-keyword">define</span> NAPI_VERSION 3</span> 631 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span></code></pre> 632 <p>This restricts the Node-API surface to just the functionality that was available 633 in the specified (and earlier) versions.</p> 634 <p>Some of the Node-API surface is experimental and requires explicit opt-in:</p> 635 <pre><code class="language-c"><span class="hljs-meta">#<span class="hljs-keyword">define</span> NAPI_EXPERIMENTAL</span> 636 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span></code></pre> 637 <p>In this case the entire API surface, including any experimental APIs, will be 638 available to the module code.</p> 639 </section><section><h3>Node-API version matrix<span><a class="mark" href="#n_api_node_api_version_matrix" id="n_api_node_api_version_matrix">#</a></span></h3> 640 <p>Node-API versions are additive and versioned independently from Node.js. 641 Version 4 is an extension to version 3 in that it has all of the APIs 642 from version 3 with some additions. This means that it is not necessary 643 to recompile for new versions of Node.js which are 644 listed as supporting a later version.</p> 645 <!-- For accessibility purposes, this table needs row headers. That means we 646 can't do it in markdown. Hence, the raw HTML. --> 647 <table> 648 <tbody><tr> 649 <td></td> 650 <th scope="col">1</th> 651 <th scope="col">2</th> 652 <th scope="col">3</th> 653 </tr> 654 <tr> 655 <th scope="row">v6.x</th> 656 <td></td> 657 <td></td> 658 <td>v6.14.2*</td> 659 </tr> 660 <tr> 661 <th scope="row">v8.x</th> 662 <td>v8.6.0**</td> 663 <td>v8.10.0*</td> 664 <td>v8.11.2</td> 665 </tr> 666 <tr> 667 <th scope="row">v9.x</th> 668 <td>v9.0.0*</td> 669 <td>v9.3.0*</td> 670 <td>v9.11.0*</td> 671 </tr> 672 <tr> 673 <th scope="row">≥ v10.x</th> 674 <td>all releases</td> 675 <td>all releases</td> 676 <td>all releases</td> 677 </tr> 678 </tbody></table> 679 <table> 680 <tbody><tr> 681 <td></td> 682 <th scope="col">4</th> 683 <th scope="col">5</th> 684 <th scope="col">6</th> 685 <th scope="col">7</th> 686 <th scope="col">8</th> 687 </tr> 688 <tr> 689 <th scope="row">v10.x</th> 690 <td>v10.16.0</td> 691 <td>v10.17.0</td> 692 <td>v10.20.0</td> 693 <td>v10.23.0</td> 694 <td></td> 695 </tr> 696 <tr> 697 <th scope="row">v11.x</th> 698 <td>v11.8.0</td> 699 <td></td> 700 <td></td> 701 <td></td> 702 <td></td> 703 </tr> 704 <tr> 705 <th scope="row">v12.x</th> 706 <td>v12.0.0</td> 707 <td>v12.11.0</td> 708 <td>v12.17.0</td> 709 <td>v12.19.0</td> 710 <td>v12.22.0</td> 711 </tr> 712 <tr> 713 <th scope="row">v13.x</th> 714 <td>v13.0.0</td> 715 <td>v13.0.0</td> 716 <td></td> 717 <td></td> 718 <td></td> 719 </tr> 720 <tr> 721 <th scope="row">v14.x</th> 722 <td>v14.0.0</td> 723 <td>v14.0.0</td> 724 <td>v14.0.0</td> 725 <td>v14.12.0</td> 726 <td>v14.17.0</td> 727 </tr> 728 <tr> 729 <th scope="row">v15.x</th> 730 <td>v15.0.0</td> 731 <td>v15.0.0</td> 732 <td>v15.0.0</td> 733 <td>v15.0.0</td> 734 <td>v15.12.0</td> 735 </tr> 736 <tr> 737 <th scope="row">v16.x</th> 738 <td>v16.0.0</td> 739 <td>v16.0.0</td> 740 <td>v16.0.0</td> 741 <td>v16.0.0</td> 742 <td>v16.0.0</td> 743 </tr> 744 </tbody></table> 745 <p>* Node-API was experimental.</p> 746 <p>** Node.js 8.0.0 included Node-API as experimental. It was released as 747 Node-API version 1 but continued to evolve until Node.js 8.6.0. The API is 748 different in versions prior to Node.js 8.6.0. We recommend Node-API version 3 or 749 later.</p> 750 <p>Each API documented for Node-API will have a header named <code>added in:</code>, and APIs 751 which are stable will have the additional header <code>Node-API version:</code>. 752 APIs are directly usable when using a Node.js version which supports 753 the Node-API version shown in <code>Node-API version:</code> or higher. 754 When using a Node.js version that does not support the 755 <code>Node-API version:</code> listed or if there is no <code>Node-API version:</code> listed, 756 then the API will only be available if 757 <code>#define NAPI_EXPERIMENTAL</code> precedes the inclusion of <code>node_api.h</code> 758 or <code>js_native_api.h</code>. If an API appears not to be available on 759 a version of Node.js which is later than the one shown in <code>added in:</code> then 760 this is most likely the reason for the apparent absence.</p> 761 <p>The Node-APIs associated strictly with accessing ECMAScript features from native 762 code can be found separately in <code>js_native_api.h</code> and <code>js_native_api_types.h</code>. 763 The APIs defined in these headers are included in <code>node_api.h</code> and 764 <code>node_api_types.h</code>. The headers are structured in this way in order to allow 765 implementations of Node-API outside of Node.js. For those implementations the 766 Node.js specific APIs may not be applicable.</p> 767 <p>The Node.js-specific parts of an addon can be separated from the code that 768 exposes the actual functionality to the JavaScript environment so that the 769 latter may be used with multiple implementations of Node-API. In the example 770 below, <code>addon.c</code> and <code>addon.h</code> refer only to <code>js_native_api.h</code>. This ensures 771 that <code>addon.c</code> can be reused to compile against either the Node.js 772 implementation of Node-API or any implementation of Node-API outside of Node.js.</p> 773 <p><code>addon_node.c</code> is a separate file that contains the Node.js specific entry point 774 to the addon and which instantiates the addon by calling into <code>addon.c</code> when the 775 addon is loaded into a Node.js environment.</p> 776 <pre><code class="language-c"><span class="hljs-comment">// addon.h</span> 777 <span class="hljs-meta">#<span class="hljs-keyword">ifndef</span> _ADDON_H_</span> 778 <span class="hljs-meta">#<span class="hljs-keyword">define</span> _ADDON_H_</span> 779 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><js_native_api.h></span></span> 780 napi_value <span class="hljs-title function_">create_addon</span><span class="hljs-params">(napi_env env)</span>; 781 <span class="hljs-meta">#<span class="hljs-keyword">endif</span> <span class="hljs-comment">// _ADDON_H_</span></span></code></pre> 782 <pre><code class="language-c"><span class="hljs-comment">// addon.c</span> 783 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string">"addon.h"</span></span> 784 785 <span class="hljs-meta">#<span class="hljs-keyword">define</span> NAPI_CALL(env, call) \ 786 do { \ 787 napi_status status = (call); \ 788 <span class="hljs-keyword">if</span> (status != napi_ok) { \ 789 const napi_extended_error_info* error_info = NULL; \ 790 napi_get_last_error_info((env), &error_info); \ 791 bool is_pending; \ 792 napi_is_exception_pending((env), &is_pending); \ 793 <span class="hljs-keyword">if</span> (!is_pending) { \ 794 const char* message = (error_info->error_message == NULL) \ 795 ? <span class="hljs-string">"empty error message"</span> \ 796 : error_info->error_message; \ 797 napi_throw_error((env), NULL, message); \ 798 return NULL; \ 799 } \ 800 } \ 801 } while(0)</span> 802 803 <span class="hljs-keyword">static</span> napi_value 804 <span class="hljs-title function_">DoSomethingUseful</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 805 <span class="hljs-comment">// Do something useful.</span> 806 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 807 } 808 809 napi_value <span class="hljs-title function_">create_addon</span><span class="hljs-params">(napi_env env)</span> { 810 napi_value result; 811 NAPI_CALL(env, napi_create_object(env, &result)); 812 813 napi_value exported_function; 814 NAPI_CALL(env, napi_create_function(env, 815 <span class="hljs-string">"doSomethingUseful"</span>, 816 NAPI_AUTO_LENGTH, 817 DoSomethingUseful, 818 <span class="hljs-literal">NULL</span>, 819 &exported_function)); 820 821 NAPI_CALL(env, napi_set_named_property(env, 822 result, 823 <span class="hljs-string">"doSomethingUseful"</span>, 824 exported_function)); 825 826 <span class="hljs-keyword">return</span> result; 827 }</code></pre> 828 <pre><code class="language-c"><span class="hljs-comment">// addon_node.c</span> 829 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span> 830 <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string">"addon.h"</span></span> 831 832 NAPI_MODULE_INIT() { 833 <span class="hljs-comment">// This function body is expected to return a `napi_value`.</span> 834 <span class="hljs-comment">// The variables `napi_env env` and `napi_value exports` may be used within</span> 835 <span class="hljs-comment">// the body, as they are provided by the definition of `NAPI_MODULE_INIT()`.</span> 836 <span class="hljs-keyword">return</span> create_addon(env); 837 }</code></pre> 838 </section><section><h3>Environment life cycle APIs<span><a class="mark" href="#n_api_environment_life_cycle_apis" id="n_api_environment_life_cycle_apis">#</a></span></h3> 839 <p><a href="https://tc39.es/ecma262/#sec-agents">Section 8.7</a> of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a> defines the concept 840 of an "Agent" as a self-contained environment in which JavaScript code runs. 841 Multiple such Agents may be started and terminated either concurrently or in 842 sequence by the process.</p> 843 <p>A Node.js environment corresponds to an ECMAScript Agent. In the main process, 844 an environment is created at startup, and additional environments can be created 845 on separate threads to serve as <a href="https://nodejs.org/api/worker_threads.html">worker threads</a>. When Node.js is embedded in 846 another application, the main thread of the application may also construct and 847 destroy a Node.js environment multiple times during the life cycle of the 848 application process such that each Node.js environment created by the 849 application may, in turn, during its life cycle create and destroy additional 850 environments as worker threads.</p> 851 <p>From the perspective of a native addon this means that the bindings it provides 852 may be called multiple times, from multiple contexts, and even concurrently from 853 multiple threads.</p> 854 <p>Native addons may need to allocate global state which they use during 855 their entire life cycle such that the state must be unique to each instance of 856 the addon.</p> 857 <p>To this end, Node-API provides a way to allocate data such that its life cycle 858 is tied to the life cycle of the Agent.</p> 859 <h4>napi_set_instance_data<span><a class="mark" href="#n_api_napi_set_instance_data" id="n_api_napi_set_instance_data">#</a></span></h4> 860 <div class="api_metadata"> 861 <span>Added in: v12.8.0, v10.20.0</span> 862 <span>N-API version: 6</span> 863 </div> 864 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_instance_data</span><span class="hljs-params">(napi_env env, 865 <span class="hljs-type">void</span>* data, 866 napi_finalize finalize_cb, 867 <span class="hljs-type">void</span>* finalize_hint)</span>;</code></pre> 868 <ul> 869 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 870 <li><code>[in] data</code>: The data item to make available to bindings of this instance.</li> 871 <li><code>[in] finalize_cb</code>: The function to call when the environment is being torn 872 down. The function receives <code>data</code> so that it might free it. 873 <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 874 <li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 875 collection.</li> 876 </ul> 877 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 878 <p>This API associates <code>data</code> with the currently running Agent. <code>data</code> can later 879 be retrieved using <code>napi_get_instance_data()</code>. Any existing data associated with 880 the currently running Agent which was set by means of a previous call to 881 <code>napi_set_instance_data()</code> will be overwritten. If a <code>finalize_cb</code> was provided 882 by the previous call, it will not be called.</p> 883 <h4>napi_get_instance_data<span><a class="mark" href="#n_api_napi_get_instance_data" id="n_api_napi_get_instance_data">#</a></span></h4> 884 <div class="api_metadata"> 885 <span>Added in: v12.8.0, v10.20.0</span> 886 <span>N-API version: 6</span> 887 </div> 888 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_instance_data</span><span class="hljs-params">(napi_env env, 889 <span class="hljs-type">void</span>** data)</span>;</code></pre> 890 <ul> 891 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 892 <li><code>[out] data</code>: The data item that was previously associated with the currently 893 running Agent by a call to <code>napi_set_instance_data()</code>.</li> 894 </ul> 895 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 896 <p>This API retrieves data that was previously associated with the currently 897 running Agent via <code>napi_set_instance_data()</code>. If no data is set, the call will 898 succeed and <code>data</code> will be set to <code>NULL</code>.</p> 899 </section><section><h3>Basic Node-API data types<span><a class="mark" href="#n_api_basic_node_api_data_types" id="n_api_basic_node_api_data_types">#</a></span></h3> 900 <p>Node-API exposes the following fundamental datatypes as abstractions that are 901 consumed by the various APIs. These APIs should be treated as opaque, 902 introspectable only with other Node-API calls.</p> 903 <h4>napi_status<span><a class="mark" href="#n_api_napi_status" id="n_api_napi_status">#</a></span></h4> 904 <div class="api_metadata"> 905 <span>Added in: v8.0.0</span> 906 <span>N-API version: 1</span> 907 </div> 908 <p>Integral status code indicating the success or failure of a Node-API call. 909 Currently, the following status codes are supported.</p> 910 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 911 napi_ok, 912 napi_invalid_arg, 913 napi_object_expected, 914 napi_string_expected, 915 napi_name_expected, 916 napi_function_expected, 917 napi_number_expected, 918 napi_boolean_expected, 919 napi_array_expected, 920 napi_generic_failure, 921 napi_pending_exception, 922 napi_cancelled, 923 napi_escape_called_twice, 924 napi_handle_scope_mismatch, 925 napi_callback_scope_mismatch, 926 napi_queue_full, 927 napi_closing, 928 napi_bigint_expected, 929 napi_date_expected, 930 napi_arraybuffer_expected, 931 napi_detachable_arraybuffer_expected, 932 napi_would_deadlock, <span class="hljs-comment">/* unused */</span> 933 } napi_status;</code></pre> 934 <p>If additional information is required upon an API returning a failed status, 935 it can be obtained by calling <code>napi_get_last_error_info</code>.</p> 936 <h4>napi_extended_error_info<span><a class="mark" href="#n_api_napi_extended_error_info" id="n_api_napi_extended_error_info">#</a></span></h4> 937 <div class="api_metadata"> 938 <span>Added in: v8.0.0</span> 939 <span>N-API version: 1</span> 940 </div> 941 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 942 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* error_message; 943 <span class="hljs-type">void</span>* engine_reserved; 944 <span class="hljs-type">uint32_t</span> engine_error_code; 945 napi_status error_code; 946 } napi_extended_error_info;</code></pre> 947 <ul> 948 <li><code>error_message</code>: UTF8-encoded string containing a VM-neutral description of 949 the error.</li> 950 <li><code>engine_reserved</code>: Reserved for VM-specific error details. This is currently 951 not implemented for any VM.</li> 952 <li><code>engine_error_code</code>: VM-specific error code. This is currently 953 not implemented for any VM.</li> 954 <li><code>error_code</code>: The Node-API status code that originated with the last error.</li> 955 </ul> 956 <p>See the <a href="#n_api_error_handling">Error handling</a> section for additional information.</p> 957 <h4>napi_env<span><a class="mark" href="#n_api_napi_env" id="n_api_napi_env">#</a></span></h4> 958 <p><code>napi_env</code> is used to represent a context that the underlying Node-API 959 implementation can use to persist VM-specific state. This structure is passed 960 to native functions when they're invoked, and it must be passed back when 961 making Node-API calls. Specifically, the same <code>napi_env</code> that was passed in when 962 the initial native function was called must be passed to any subsequent 963 nested Node-API calls. Caching the <code>napi_env</code> for the purpose of general reuse, 964 and passing the <code>napi_env</code> between instances of the same addon running on 965 different <a href="worker_threads.html#worker_threads_class_worker"><code>Worker</code></a> threads is not allowed. The <code>napi_env</code> becomes invalid 966 when an instance of a native addon is unloaded. Notification of this event is 967 delivered through the callbacks given to <a href="#n_api_napi_add_env_cleanup_hook"><code>napi_add_env_cleanup_hook</code></a> and 968 <a href="#n_api_napi_set_instance_data"><code>napi_set_instance_data</code></a>.</p> 969 <h4>napi_value<span><a class="mark" href="#n_api_napi_value" id="n_api_napi_value">#</a></span></h4> 970 <p>This is an opaque pointer that is used to represent a JavaScript value.</p> 971 <h4>napi_threadsafe_function<span><a class="mark" href="#n_api_napi_threadsafe_function" id="n_api_napi_threadsafe_function">#</a></span></h4> 972 <div class="api_metadata"> 973 <span>Added in: v10.6.0</span> 974 <span>N-API version: 4</span> 975 </div> 976 <p>This is an opaque pointer that represents a JavaScript function which can be 977 called asynchronously from multiple threads via 978 <code>napi_call_threadsafe_function()</code>.</p> 979 <h4>napi_threadsafe_function_release_mode<span><a class="mark" href="#n_api_napi_threadsafe_function_release_mode" id="n_api_napi_threadsafe_function_release_mode">#</a></span></h4> 980 <div class="api_metadata"> 981 <span>Added in: v10.6.0</span> 982 <span>N-API version: 4</span> 983 </div> 984 <p>A value to be given to <code>napi_release_threadsafe_function()</code> to indicate whether 985 the thread-safe function is to be closed immediately (<code>napi_tsfn_abort</code>) or 986 merely released (<code>napi_tsfn_release</code>) and thus available for subsequent use via 987 <code>napi_acquire_threadsafe_function()</code> and <code>napi_call_threadsafe_function()</code>.</p> 988 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 989 napi_tsfn_release, 990 napi_tsfn_abort 991 } napi_threadsafe_function_release_mode;</code></pre> 992 <h4>napi_threadsafe_function_call_mode<span><a class="mark" href="#n_api_napi_threadsafe_function_call_mode" id="n_api_napi_threadsafe_function_call_mode">#</a></span></h4> 993 <div class="api_metadata"> 994 <span>Added in: v10.6.0</span> 995 <span>N-API version: 4</span> 996 </div> 997 <p>A value to be given to <code>napi_call_threadsafe_function()</code> to indicate whether 998 the call should block whenever the queue associated with the thread-safe 999 function is full.</p> 1000 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 1001 napi_tsfn_nonblocking, 1002 napi_tsfn_blocking 1003 } napi_threadsafe_function_call_mode;</code></pre> 1004 <h4>Node-API memory management types<span><a class="mark" href="#n_api_node_api_memory_management_types" id="n_api_node_api_memory_management_types">#</a></span></h4> 1005 <h5>napi_handle_scope<span><a class="mark" href="#n_api_napi_handle_scope" id="n_api_napi_handle_scope">#</a></span></h5> 1006 <p>This is an abstraction used to control and modify the lifetime of objects 1007 created within a particular scope. In general, Node-API values are created 1008 within the context of a handle scope. When a native method is called from 1009 JavaScript, a default handle scope will exist. If the user does not explicitly 1010 create a new handle scope, Node-API values will be created in the default handle 1011 scope. For any invocations of code outside the execution of a native method 1012 (for instance, during a libuv callback invocation), the module is required to 1013 create a scope before invoking any functions that can result in the creation 1014 of JavaScript values.</p> 1015 <p>Handle scopes are created using <a href="#n_api_napi_open_handle_scope"><code>napi_open_handle_scope</code></a> and are destroyed 1016 using <a href="#n_api_napi_close_handle_scope"><code>napi_close_handle_scope</code></a>. Closing the scope can indicate to the GC 1017 that all <code>napi_value</code>s created during the lifetime of the handle scope are no 1018 longer referenced from the current stack frame.</p> 1019 <p>For more details, review the <a href="#n_api_object_lifetime_management">Object lifetime management</a>.</p> 1020 <h5>napi_escapable_handle_scope<span><a class="mark" href="#n_api_napi_escapable_handle_scope" id="n_api_napi_escapable_handle_scope">#</a></span></h5> 1021 <div class="api_metadata"> 1022 <span>Added in: v8.0.0</span> 1023 <span>N-API version: 1</span> 1024 </div> 1025 <p>Escapable handle scopes are a special type of handle scope to return values 1026 created within a particular handle scope to a parent scope.</p> 1027 <h5>napi_ref<span><a class="mark" href="#n_api_napi_ref" id="n_api_napi_ref">#</a></span></h5> 1028 <div class="api_metadata"> 1029 <span>Added in: v8.0.0</span> 1030 <span>N-API version: 1</span> 1031 </div> 1032 <p>This is the abstraction to use to reference a <code>napi_value</code>. This allows for 1033 users to manage the lifetimes of JavaScript values, including defining their 1034 minimum lifetimes explicitly.</p> 1035 <p>For more details, review the <a href="#n_api_object_lifetime_management">Object lifetime management</a>.</p> 1036 <h5>napi_type_tag<span><a class="mark" href="#n_api_napi_type_tag" id="n_api_napi_type_tag">#</a></span></h5> 1037 <div class="api_metadata"> 1038 <span>Added in: v14.8.0, v12.19.0</span> 1039 <span>N-API version: 8</span> 1040 </div> 1041 <p>A 128-bit value stored as two unsigned 64-bit integers. It serves as a UUID 1042 with which JavaScript objects can be "tagged" in order to ensure that they are 1043 of a certain type. This is a stronger check than <a href="#n_api_napi_instanceof"><code>napi_instanceof</code></a>, because 1044 the latter can report a false positive if the object's prototype has been 1045 manipulated. Type-tagging is most useful in conjunction with <a href="#n_api_napi_wrap"><code>napi_wrap</code></a> 1046 because it ensures that the pointer retrieved from a wrapped object can be 1047 safely cast to the native type corresponding to the type tag that had been 1048 previously applied to the JavaScript object.</p> 1049 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 1050 <span class="hljs-type">uint64_t</span> lower; 1051 <span class="hljs-type">uint64_t</span> upper; 1052 } napi_type_tag;</code></pre> 1053 <h5>napi_async_cleanup_hook_handle<span><a class="mark" href="#n_api_napi_async_cleanup_hook_handle" id="n_api_napi_async_cleanup_hook_handle">#</a></span></h5> 1054 <div class="api_metadata"> 1055 <span>Added in: v14.10.0</span> 1056 </div> 1057 <p>An opaque value returned by <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a>. It must be passed 1058 to <a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a> when the chain of asynchronous cleanup 1059 events completes.</p> 1060 <h4>Node-API callback types<span><a class="mark" href="#n_api_node_api_callback_types" id="n_api_node_api_callback_types">#</a></span></h4> 1061 <h5>napi_callback_info<span><a class="mark" href="#n_api_napi_callback_info" id="n_api_napi_callback_info">#</a></span></h5> 1062 <div class="api_metadata"> 1063 <span>Added in: v8.0.0</span> 1064 <span>N-API version: 1</span> 1065 </div> 1066 <p>Opaque datatype that is passed to a callback function. It can be used for 1067 getting additional information about the context in which the callback was 1068 invoked.</p> 1069 <h5>napi_callback<span><a class="mark" href="#n_api_napi_callback" id="n_api_napi_callback">#</a></span></h5> 1070 <div class="api_metadata"> 1071 <span>Added in: v8.0.0</span> 1072 <span>N-API version: 1</span> 1073 </div> 1074 <p>Function pointer type for user-provided native functions which are to be 1075 exposed to JavaScript via Node-API. Callback functions should satisfy the 1076 following signature:</p> 1077 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-title function_">napi_value</span> <span class="hljs-params">(*napi_callback)</span><span class="hljs-params">(napi_env, napi_callback_info)</span>;</code></pre> 1078 <p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1079 handle and/or callback scope inside a <code>napi_callback</code> is not necessary.</p> 1080 <h5>napi_finalize<span><a class="mark" href="#n_api_napi_finalize" id="n_api_napi_finalize">#</a></span></h5> 1081 <div class="api_metadata"> 1082 <span>Added in: v8.0.0</span> 1083 <span>N-API version: 1</span> 1084 </div> 1085 <p>Function pointer type for add-on provided functions that allow the user to be 1086 notified when externally-owned data is ready to be cleaned up because the 1087 object with which it was associated with, has been garbage-collected. The user 1088 must provide a function satisfying the following signature which would get 1089 called upon the object's collection. Currently, <code>napi_finalize</code> can be used for 1090 finding out when objects that have external data are collected.</p> 1091 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-title function_">void</span> <span class="hljs-params">(*napi_finalize)</span><span class="hljs-params">(napi_env env, 1092 <span class="hljs-type">void</span>* finalize_data, 1093 <span class="hljs-type">void</span>* finalize_hint)</span>;</code></pre> 1094 <p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1095 handle and/or callback scope inside the function body is not necessary.</p> 1096 <h5>napi_async_execute_callback<span><a class="mark" href="#n_api_napi_async_execute_callback" id="n_api_napi_async_execute_callback">#</a></span></h5> 1097 <div class="api_metadata"> 1098 <span>Added in: v8.0.0</span> 1099 <span>N-API version: 1</span> 1100 </div> 1101 <p>Function pointer used with functions that support asynchronous 1102 operations. Callback functions must satisfy the following signature:</p> 1103 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-title function_">void</span> <span class="hljs-params">(*napi_async_execute_callback)</span><span class="hljs-params">(napi_env env, <span class="hljs-type">void</span>* data)</span>;</code></pre> 1104 <p>Implementations of this function must avoid making Node-API calls that execute 1105 JavaScript or interact with JavaScript objects. Node-API calls should be in the 1106 <code>napi_async_complete_callback</code> instead. Do not use the <code>napi_env</code> parameter as 1107 it will likely result in execution of JavaScript.</p> 1108 <h5>napi_async_complete_callback<span><a class="mark" href="#n_api_napi_async_complete_callback" id="n_api_napi_async_complete_callback">#</a></span></h5> 1109 <div class="api_metadata"> 1110 <span>Added in: v8.0.0</span> 1111 <span>N-API version: 1</span> 1112 </div> 1113 <p>Function pointer used with functions that support asynchronous 1114 operations. Callback functions must satisfy the following signature:</p> 1115 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-title function_">void</span> <span class="hljs-params">(*napi_async_complete_callback)</span><span class="hljs-params">(napi_env env, 1116 napi_status status, 1117 <span class="hljs-type">void</span>* data)</span>;</code></pre> 1118 <p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1119 handle and/or callback scope inside the function body is not necessary.</p> 1120 <h5>napi_threadsafe_function_call_js<span><a class="mark" href="#n_api_napi_threadsafe_function_call_js" id="n_api_napi_threadsafe_function_call_js">#</a></span></h5> 1121 <div class="api_metadata"> 1122 <span>Added in: v10.6.0</span> 1123 <span>N-API version: 4</span> 1124 </div> 1125 <p>Function pointer used with asynchronous thread-safe function calls. The callback 1126 will be called on the main thread. Its purpose is to use a data item arriving 1127 via the queue from one of the secondary threads to construct the parameters 1128 necessary for a call into JavaScript, usually via <code>napi_call_function</code>, and then 1129 make the call into JavaScript.</p> 1130 <p>The data arriving from the secondary thread via the queue is given in the <code>data</code> 1131 parameter and the JavaScript function to call is given in the <code>js_callback</code> 1132 parameter.</p> 1133 <p>Node-API sets up the environment prior to calling this callback, so it is 1134 sufficient to call the JavaScript function via <code>napi_call_function</code> rather than 1135 via <code>napi_make_callback</code>.</p> 1136 <p>Callback functions must satisfy the following signature:</p> 1137 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-title function_">void</span> <span class="hljs-params">(*napi_threadsafe_function_call_js)</span><span class="hljs-params">(napi_env env, 1138 napi_value js_callback, 1139 <span class="hljs-type">void</span>* context, 1140 <span class="hljs-type">void</span>* data)</span>;</code></pre> 1141 <ul> 1142 <li><code>[in] env</code>: The environment to use for API calls, or <code>NULL</code> if the thread-safe 1143 function is being torn down and <code>data</code> may need to be freed.</li> 1144 <li><code>[in] js_callback</code>: The JavaScript function to call, or <code>NULL</code> if the 1145 thread-safe function is being torn down and <code>data</code> may need to be freed. It 1146 may also be <code>NULL</code> if the thread-safe function was created without 1147 <code>js_callback</code>.</li> 1148 <li><code>[in] context</code>: The optional data with which the thread-safe function was 1149 created.</li> 1150 <li><code>[in] data</code>: Data created by the secondary thread. It is the responsibility of 1151 the callback to convert this native data to JavaScript values (with Node-API 1152 functions) that can be passed as parameters when <code>js_callback</code> is invoked. 1153 This pointer is managed entirely by the threads and this callback. Thus this 1154 callback should free the data.</li> 1155 </ul> 1156 <p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1157 handle and/or callback scope inside the function body is not necessary.</p> 1158 <h5>napi_async_cleanup_hook<span><a class="mark" href="#n_api_napi_async_cleanup_hook" id="n_api_napi_async_cleanup_hook">#</a></span></h5> 1159 <div class="api_metadata"> 1160 <span>Added in: v14.10.0</span> 1161 </div> 1162 <p>Function pointer used with <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a>. It will be called 1163 when the environment is being torn down.</p> 1164 <p>Callback functions must satisfy the following signature:</p> 1165 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-title function_">void</span> <span class="hljs-params">(*napi_async_cleanup_hook)</span><span class="hljs-params">(napi_async_cleanup_hook_handle handle, 1166 <span class="hljs-type">void</span>* data)</span>;</code></pre> 1167 <ul> 1168 <li><code>[in] handle</code>: The handle that must be passed to 1169 <a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a> after completion of the asynchronous 1170 cleanup.</li> 1171 <li><code>[in] data</code>: The data that was passed to <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a>.</li> 1172 </ul> 1173 <p>The body of the function should initiate the asynchronous cleanup actions at the 1174 end of which <code>handle</code> must be passed in a call to 1175 <a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a>.</p> 1176 </section><section><h3>Error handling<span><a class="mark" href="#n_api_error_handling" id="n_api_error_handling">#</a></span></h3> 1177 <p>Node-API uses both return values and JavaScript exceptions for error handling. 1178 The following sections explain the approach for each case.</p> 1179 <h4>Return values<span><a class="mark" href="#n_api_return_values" id="n_api_return_values">#</a></span></h4> 1180 <p>All of the Node-API functions share the same error handling pattern. The 1181 return type of all API functions is <code>napi_status</code>.</p> 1182 <p>The return value will be <code>napi_ok</code> if the request was successful and 1183 no uncaught JavaScript exception was thrown. If an error occurred AND 1184 an exception was thrown, the <code>napi_status</code> value for the error 1185 will be returned. If an exception was thrown, and no error occurred, 1186 <code>napi_pending_exception</code> will be returned.</p> 1187 <p>In cases where a return value other than <code>napi_ok</code> or 1188 <code>napi_pending_exception</code> is returned, <a href="#n_api_napi_is_exception_pending"><code>napi_is_exception_pending</code></a> 1189 must be called to check if an exception is pending. 1190 See the section on exceptions for more details.</p> 1191 <p>The full set of possible <code>napi_status</code> values is defined 1192 in <code>napi_api_types.h</code>.</p> 1193 <p>The <code>napi_status</code> return value provides a VM-independent representation of 1194 the error which occurred. In some cases it is useful to be able to get 1195 more detailed information, including a string representing the error as well as 1196 VM (engine)-specific information.</p> 1197 <p>In order to retrieve this information <a href="#n_api_napi_get_last_error_info"><code>napi_get_last_error_info</code></a> 1198 is provided which returns a <code>napi_extended_error_info</code> structure. 1199 The format of the <code>napi_extended_error_info</code> structure is as follows:</p> 1200 <div class="api_metadata"> 1201 <span>Added in: v8.0.0</span> 1202 <span>N-API version: 1</span> 1203 </div> 1204 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> <span class="hljs-title">napi_extended_error_info</span> {</span> 1205 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* error_message; 1206 <span class="hljs-type">void</span>* engine_reserved; 1207 <span class="hljs-type">uint32_t</span> engine_error_code; 1208 napi_status error_code; 1209 };</code></pre> 1210 <ul> 1211 <li><code>error_message</code>: Textual representation of the error that occurred.</li> 1212 <li><code>engine_reserved</code>: Opaque handle reserved for engine use only.</li> 1213 <li><code>engine_error_code</code>: VM specific error code.</li> 1214 <li><code>error_code</code>: Node-API status code for the last error.</li> 1215 </ul> 1216 <p><a href="#n_api_napi_get_last_error_info"><code>napi_get_last_error_info</code></a> returns the information for the last 1217 Node-API call that was made.</p> 1218 <p>Do not rely on the content or format of any of the extended information as it 1219 is not subject to SemVer and may change at any time. It is intended only for 1220 logging purposes.</p> 1221 <h5>napi_get_last_error_info<span><a class="mark" href="#n_api_napi_get_last_error_info" id="n_api_napi_get_last_error_info">#</a></span></h5> 1222 <div class="api_metadata"> 1223 <span>Added in: v8.0.0</span> 1224 <span>N-API version: 1</span> 1225 </div> 1226 <pre><code class="language-c">napi_status 1227 <span class="hljs-title function_">napi_get_last_error_info</span><span class="hljs-params">(napi_env env, 1228 <span class="hljs-keyword">const</span> napi_extended_error_info** result)</span>;</code></pre> 1229 <ul> 1230 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1231 <li><code>[out] result</code>: The <code>napi_extended_error_info</code> structure with more 1232 information about the error.</li> 1233 </ul> 1234 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1235 <p>This API retrieves a <code>napi_extended_error_info</code> structure with information 1236 about the last error that occurred.</p> 1237 <p>The content of the <code>napi_extended_error_info</code> returned is only valid up until 1238 a Node-API function is called on the same <code>env</code>.</p> 1239 <p>Do not rely on the content or format of any of the extended information as it 1240 is not subject to SemVer and may change at any time. It is intended only for 1241 logging purposes.</p> 1242 <p>This API can be called even if there is a pending JavaScript exception.</p> 1243 <h4>Exceptions<span><a class="mark" href="#n_api_exceptions" id="n_api_exceptions">#</a></span></h4> 1244 <p>Any Node-API function call may result in a pending JavaScript exception. This is 1245 the case for any of the API functions, even those that may not cause the 1246 execution of JavaScript.</p> 1247 <p>If the <code>napi_status</code> returned by a function is <code>napi_ok</code> then no 1248 exception is pending and no additional action is required. If the 1249 <code>napi_status</code> returned is anything other than <code>napi_ok</code> or 1250 <code>napi_pending_exception</code>, in order to try to recover and continue 1251 instead of simply returning immediately, <a href="#n_api_napi_is_exception_pending"><code>napi_is_exception_pending</code></a> 1252 must be called in order to determine if an exception is pending or not.</p> 1253 <p>In many cases when a Node-API function is called and an exception is 1254 already pending, the function will return immediately with a 1255 <code>napi_status</code> of <code>napi_pending_exception</code>. However, this is not the case 1256 for all functions. Node-API allows a subset of the functions to be 1257 called to allow for some minimal cleanup before returning to JavaScript. 1258 In that case, <code>napi_status</code> will reflect the status for the function. It 1259 will not reflect previous pending exceptions. To avoid confusion, check 1260 the error status after every function call.</p> 1261 <p>When an exception is pending one of two approaches can be employed.</p> 1262 <p>The first approach is to do any appropriate cleanup and then return so that 1263 execution will return to JavaScript. As part of the transition back to 1264 JavaScript, the exception will be thrown at the point in the JavaScript 1265 code where the native method was invoked. The behavior of most Node-API calls 1266 is unspecified while an exception is pending, and many will simply return 1267 <code>napi_pending_exception</code>, so do as little as possible and then return to 1268 JavaScript where the exception can be handled.</p> 1269 <p>The second approach is to try to handle the exception. There will be cases 1270 where the native code can catch the exception, take the appropriate action, 1271 and then continue. This is only recommended in specific cases 1272 where it is known that the exception can be safely handled. In these 1273 cases <a href="#n_api_napi_get_and_clear_last_exception"><code>napi_get_and_clear_last_exception</code></a> can be used to get and 1274 clear the exception. On success, result will contain the handle to 1275 the last JavaScript <code>Object</code> thrown. If it is determined, after 1276 retrieving the exception, the exception cannot be handled after all 1277 it can be re-thrown it with <a href="#n_api_napi_throw"><code>napi_throw</code></a> where error is the 1278 JavaScript value to be thrown.</p> 1279 <p>The following utility functions are also available in case native code 1280 needs to throw an exception or determine if a <code>napi_value</code> is an instance 1281 of a JavaScript <code>Error</code> object: <a href="#n_api_napi_throw_error"><code>napi_throw_error</code></a>, 1282 <a href="#n_api_napi_throw_type_error"><code>napi_throw_type_error</code></a>, <a href="#n_api_napi_throw_range_error"><code>napi_throw_range_error</code></a> and 1283 <a href="#n_api_napi_is_error"><code>napi_is_error</code></a>.</p> 1284 <p>The following utility functions are also available in case native 1285 code needs to create an <code>Error</code> object: <a href="#n_api_napi_create_error"><code>napi_create_error</code></a>, 1286 <a href="#n_api_napi_create_type_error"><code>napi_create_type_error</code></a>, and <a href="#n_api_napi_create_range_error"><code>napi_create_range_error</code></a>, 1287 where result is the <code>napi_value</code> that refers to the newly created 1288 JavaScript <code>Error</code> object.</p> 1289 <p>The Node.js project is adding error codes to all of the errors 1290 generated internally. The goal is for applications to use these 1291 error codes for all error checking. The associated error messages 1292 will remain, but will only be meant to be used for logging and 1293 display with the expectation that the message can change without 1294 SemVer applying. In order to support this model with Node-API, both 1295 in internal functionality and for module specific functionality 1296 (as its good practice), the <code>throw_</code> and <code>create_</code> functions 1297 take an optional code parameter which is the string for the code 1298 to be added to the error object. If the optional parameter is <code>NULL</code> 1299 then no code will be associated with the error. If a code is provided, 1300 the name associated with the error is also updated to be:</p> 1301 <pre><code class="language-text">originalName [code]</code></pre> 1302 <p>where <code>originalName</code> is the original name associated with the error 1303 and <code>code</code> is the code that was provided. For example, if the code 1304 is <code>'ERR_ERROR_1'</code> and a <code>TypeError</code> is being created the name will be:</p> 1305 <pre><code class="language-text">TypeError [ERR_ERROR_1]</code></pre> 1306 <h5>napi_throw<span><a class="mark" href="#n_api_napi_throw" id="n_api_napi_throw">#</a></span></h5> 1307 <div class="api_metadata"> 1308 <span>Added in: v8.0.0</span> 1309 <span>N-API version: 1</span> 1310 </div> 1311 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_throw</span><span class="hljs-params">(napi_env env, napi_value error)</span>;</code></pre> 1312 <ul> 1313 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1314 <li><code>[in] error</code>: The JavaScript value to be thrown.</li> 1315 </ul> 1316 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1317 <p>This API throws the JavaScript value provided.</p> 1318 <h5>napi_throw_error<span><a class="mark" href="#n_api_napi_throw_error" id="n_api_napi_throw_error">#</a></span></h5> 1319 <div class="api_metadata"> 1320 <span>Added in: v8.0.0</span> 1321 <span>N-API version: 1</span> 1322 </div> 1323 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_throw_error</span><span class="hljs-params">(napi_env env, 1324 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* code, 1325 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* msg)</span>;</code></pre> 1326 <ul> 1327 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1328 <li><code>[in] code</code>: Optional error code to be set on the error.</li> 1329 <li><code>[in] msg</code>: C string representing the text to be associated with the error.</li> 1330 </ul> 1331 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1332 <p>This API throws a JavaScript <code>Error</code> with the text provided.</p> 1333 <h5>napi_throw_type_error<span><a class="mark" href="#n_api_napi_throw_type_error" id="n_api_napi_throw_type_error">#</a></span></h5> 1334 <div class="api_metadata"> 1335 <span>Added in: v8.0.0</span> 1336 <span>N-API version: 1</span> 1337 </div> 1338 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_throw_type_error</span><span class="hljs-params">(napi_env env, 1339 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* code, 1340 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* msg)</span>;</code></pre> 1341 <ul> 1342 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1343 <li><code>[in] code</code>: Optional error code to be set on the error.</li> 1344 <li><code>[in] msg</code>: C string representing the text to be associated with the error.</li> 1345 </ul> 1346 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1347 <p>This API throws a JavaScript <code>TypeError</code> with the text provided.</p> 1348 <h5>napi_throw_range_error<span><a class="mark" href="#n_api_napi_throw_range_error" id="n_api_napi_throw_range_error">#</a></span></h5> 1349 <div class="api_metadata"> 1350 <span>Added in: v8.0.0</span> 1351 <span>N-API version: 1</span> 1352 </div> 1353 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_throw_range_error</span><span class="hljs-params">(napi_env env, 1354 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* code, 1355 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* msg)</span>;</code></pre> 1356 <ul> 1357 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1358 <li><code>[in] code</code>: Optional error code to be set on the error.</li> 1359 <li><code>[in] msg</code>: C string representing the text to be associated with the error.</li> 1360 </ul> 1361 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1362 <p>This API throws a JavaScript <code>RangeError</code> with the text provided.</p> 1363 <h5>napi_is_error<span><a class="mark" href="#n_api_napi_is_error" id="n_api_napi_is_error">#</a></span></h5> 1364 <div class="api_metadata"> 1365 <span>Added in: v8.0.0</span> 1366 <span>N-API version: 1</span> 1367 </div> 1368 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_is_error</span><span class="hljs-params">(napi_env env, 1369 napi_value value, 1370 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 1371 <ul> 1372 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1373 <li><code>[in] value</code>: The <code>napi_value</code> to be checked.</li> 1374 <li><code>[out] result</code>: Boolean value that is set to true if <code>napi_value</code> represents 1375 an error, false otherwise.</li> 1376 </ul> 1377 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1378 <p>This API queries a <code>napi_value</code> to check if it represents an error object.</p> 1379 <h5>napi_create_error<span><a class="mark" href="#n_api_napi_create_error" id="n_api_napi_create_error">#</a></span></h5> 1380 <div class="api_metadata"> 1381 <span>Added in: v8.0.0</span> 1382 <span>N-API version: 1</span> 1383 </div> 1384 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_create_error</span><span class="hljs-params">(napi_env env, 1385 napi_value code, 1386 napi_value msg, 1387 napi_value* result)</span>;</code></pre> 1388 <ul> 1389 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1390 <li><code>[in] code</code>: Optional <code>napi_value</code> with the string for the error code to be 1391 associated with the error.</li> 1392 <li><code>[in] msg</code>: <code>napi_value</code> that references a JavaScript <code>string</code> to be used as 1393 the message for the <code>Error</code>.</li> 1394 <li><code>[out] result</code>: <code>napi_value</code> representing the error created.</li> 1395 </ul> 1396 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1397 <p>This API returns a JavaScript <code>Error</code> with the text provided.</p> 1398 <h5>napi_create_type_error<span><a class="mark" href="#n_api_napi_create_type_error" id="n_api_napi_create_type_error">#</a></span></h5> 1399 <div class="api_metadata"> 1400 <span>Added in: v8.0.0</span> 1401 <span>N-API version: 1</span> 1402 </div> 1403 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_create_type_error</span><span class="hljs-params">(napi_env env, 1404 napi_value code, 1405 napi_value msg, 1406 napi_value* result)</span>;</code></pre> 1407 <ul> 1408 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1409 <li><code>[in] code</code>: Optional <code>napi_value</code> with the string for the error code to be 1410 associated with the error.</li> 1411 <li><code>[in] msg</code>: <code>napi_value</code> that references a JavaScript <code>string</code> to be used as 1412 the message for the <code>Error</code>.</li> 1413 <li><code>[out] result</code>: <code>napi_value</code> representing the error created.</li> 1414 </ul> 1415 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1416 <p>This API returns a JavaScript <code>TypeError</code> with the text provided.</p> 1417 <h5>napi_create_range_error<span><a class="mark" href="#n_api_napi_create_range_error" id="n_api_napi_create_range_error">#</a></span></h5> 1418 <div class="api_metadata"> 1419 <span>Added in: v8.0.0</span> 1420 <span>N-API version: 1</span> 1421 </div> 1422 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_create_range_error</span><span class="hljs-params">(napi_env env, 1423 napi_value code, 1424 napi_value msg, 1425 napi_value* result)</span>;</code></pre> 1426 <ul> 1427 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1428 <li><code>[in] code</code>: Optional <code>napi_value</code> with the string for the error code to be 1429 associated with the error.</li> 1430 <li><code>[in] msg</code>: <code>napi_value</code> that references a JavaScript <code>string</code> to be used as 1431 the message for the <code>Error</code>.</li> 1432 <li><code>[out] result</code>: <code>napi_value</code> representing the error created.</li> 1433 </ul> 1434 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1435 <p>This API returns a JavaScript <code>RangeError</code> with the text provided.</p> 1436 <h5>napi_get_and_clear_last_exception<span><a class="mark" href="#n_api_napi_get_and_clear_last_exception" id="n_api_napi_get_and_clear_last_exception">#</a></span></h5> 1437 <div class="api_metadata"> 1438 <span>Added in: v8.0.0</span> 1439 <span>N-API version: 1</span> 1440 </div> 1441 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_and_clear_last_exception</span><span class="hljs-params">(napi_env env, 1442 napi_value* result)</span>;</code></pre> 1443 <ul> 1444 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1445 <li><code>[out] result</code>: The exception if one is pending, <code>NULL</code> otherwise.</li> 1446 </ul> 1447 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1448 <p>This API can be called even if there is a pending JavaScript exception.</p> 1449 <h5>napi_is_exception_pending<span><a class="mark" href="#n_api_napi_is_exception_pending" id="n_api_napi_is_exception_pending">#</a></span></h5> 1450 <div class="api_metadata"> 1451 <span>Added in: v8.0.0</span> 1452 <span>N-API version: 1</span> 1453 </div> 1454 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_exception_pending</span><span class="hljs-params">(napi_env env, <span class="hljs-type">bool</span>* result)</span>;</code></pre> 1455 <ul> 1456 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1457 <li><code>[out] result</code>: Boolean value that is set to true if an exception is pending.</li> 1458 </ul> 1459 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1460 <p>This API can be called even if there is a pending JavaScript exception.</p> 1461 <h5>napi_fatal_exception<span><a class="mark" href="#n_api_napi_fatal_exception" id="n_api_napi_fatal_exception">#</a></span></h5> 1462 <div class="api_metadata"> 1463 <span>Added in: v9.10.0</span> 1464 <span>N-API version: 3</span> 1465 </div> 1466 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_fatal_exception</span><span class="hljs-params">(napi_env env, napi_value err)</span>;</code></pre> 1467 <ul> 1468 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1469 <li><code>[in] err</code>: The error that is passed to <code>'uncaughtException'</code>.</li> 1470 </ul> 1471 <p>Trigger an <code>'uncaughtException'</code> in JavaScript. Useful if an async 1472 callback throws an exception with no way to recover.</p> 1473 <h4>Fatal errors<span><a class="mark" href="#n_api_fatal_errors" id="n_api_fatal_errors">#</a></span></h4> 1474 <p>In the event of an unrecoverable error in a native module, a fatal error can be 1475 thrown to immediately terminate the process.</p> 1476 <h5>napi_fatal_error<span><a class="mark" href="#n_api_napi_fatal_error" id="n_api_napi_fatal_error">#</a></span></h5> 1477 <div class="api_metadata"> 1478 <span>Added in: v8.2.0</span> 1479 <span>N-API version: 1</span> 1480 </div> 1481 <pre><code class="language-c">NAPI_NO_RETURN <span class="hljs-type">void</span> <span class="hljs-title function_">napi_fatal_error</span><span class="hljs-params">(<span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* location, 1482 <span class="hljs-type">size_t</span> location_len, 1483 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* message, 1484 <span class="hljs-type">size_t</span> message_len)</span>;</code></pre> 1485 <ul> 1486 <li><code>[in] location</code>: Optional location at which the error occurred.</li> 1487 <li><code>[in] location_len</code>: The length of the location in bytes, or 1488 <code>NAPI_AUTO_LENGTH</code> if it is null-terminated.</li> 1489 <li><code>[in] message</code>: The message associated with the error.</li> 1490 <li><code>[in] message_len</code>: The length of the message in bytes, or <code>NAPI_AUTO_LENGTH</code> 1491 if it is null-terminated.</li> 1492 </ul> 1493 <p>The function call does not return, the process will be terminated.</p> 1494 <p>This API can be called even if there is a pending JavaScript exception.</p> 1495 </section><section><h3>Object lifetime management<span><a class="mark" href="#n_api_object_lifetime_management" id="n_api_object_lifetime_management">#</a></span></h3> 1496 <p>As Node-API calls are made, handles to objects in the heap for the underlying 1497 VM may be returned as <code>napi_values</code>. These handles must hold the 1498 objects 'live' until they are no longer required by the native code, 1499 otherwise the objects could be collected before the native code was 1500 finished using them.</p> 1501 <p>As object handles are returned they are associated with a 1502 'scope'. The lifespan for the default scope is tied to the lifespan 1503 of the native method call. The result is that, by default, handles 1504 remain valid and the objects associated with these handles will be 1505 held live for the lifespan of the native method call.</p> 1506 <p>In many cases, however, it is necessary that the handles remain valid for 1507 either a shorter or longer lifespan than that of the native method. 1508 The sections which follow describe the Node-API functions that can be used 1509 to change the handle lifespan from the default.</p> 1510 <h4>Making handle lifespan shorter than that of the native method<span><a class="mark" href="#n_api_making_handle_lifespan_shorter_than_that_of_the_native_method" id="n_api_making_handle_lifespan_shorter_than_that_of_the_native_method">#</a></span></h4> 1511 <p>It is often necessary to make the lifespan of handles shorter than 1512 the lifespan of a native method. For example, consider a native method 1513 that has a loop which iterates through the elements in a large array:</p> 1514 <pre><code class="language-c"><span class="hljs-keyword">for</span> (<span class="hljs-type">int</span> i = <span class="hljs-number">0</span>; i < <span class="hljs-number">1000000</span>; i++) { 1515 napi_value result; 1516 napi_status status = napi_get_element(env, object, i, &result); 1517 <span class="hljs-keyword">if</span> (status != napi_ok) { 1518 <span class="hljs-keyword">break</span>; 1519 } 1520 <span class="hljs-comment">// do something with element</span> 1521 }</code></pre> 1522 <p>This would result in a large number of handles being created, consuming 1523 substantial resources. In addition, even though the native code could only 1524 use the most recent handle, all of the associated objects would also be 1525 kept alive since they all share the same scope.</p> 1526 <p>To handle this case, Node-API provides the ability to establish a new 'scope' to 1527 which newly created handles will be associated. Once those handles 1528 are no longer required, the scope can be 'closed' and any handles associated 1529 with the scope are invalidated. The methods available to open/close scopes are 1530 <a href="#n_api_napi_open_handle_scope"><code>napi_open_handle_scope</code></a> and <a href="#n_api_napi_close_handle_scope"><code>napi_close_handle_scope</code></a>.</p> 1531 <p>Node-API only supports a single nested hierarchy of scopes. There is only one 1532 active scope at any time, and all new handles will be associated with that 1533 scope while it is active. Scopes must be closed in the reverse order from 1534 which they are opened. In addition, all scopes created within a native method 1535 must be closed before returning from that method.</p> 1536 <p>Taking the earlier example, adding calls to <a href="#n_api_napi_open_handle_scope"><code>napi_open_handle_scope</code></a> and 1537 <a href="#n_api_napi_close_handle_scope"><code>napi_close_handle_scope</code></a> would ensure that at most a single handle 1538 is valid throughout the execution of the loop:</p> 1539 <pre><code class="language-c"><span class="hljs-keyword">for</span> (<span class="hljs-type">int</span> i = <span class="hljs-number">0</span>; i < <span class="hljs-number">1000000</span>; i++) { 1540 napi_handle_scope scope; 1541 napi_status status = napi_open_handle_scope(env, &scope); 1542 <span class="hljs-keyword">if</span> (status != napi_ok) { 1543 <span class="hljs-keyword">break</span>; 1544 } 1545 napi_value result; 1546 status = napi_get_element(env, object, i, &result); 1547 <span class="hljs-keyword">if</span> (status != napi_ok) { 1548 <span class="hljs-keyword">break</span>; 1549 } 1550 <span class="hljs-comment">// do something with element</span> 1551 status = napi_close_handle_scope(env, scope); 1552 <span class="hljs-keyword">if</span> (status != napi_ok) { 1553 <span class="hljs-keyword">break</span>; 1554 } 1555 }</code></pre> 1556 <p>When nesting scopes, there are cases where a handle from an 1557 inner scope needs to live beyond the lifespan of that scope. Node-API supports 1558 an 'escapable scope' in order to support this case. An escapable scope 1559 allows one handle to be 'promoted' so that it 'escapes' the 1560 current scope and the lifespan of the handle changes from the current 1561 scope to that of the outer scope.</p> 1562 <p>The methods available to open/close escapable scopes are 1563 <a href="#n_api_napi_open_escapable_handle_scope"><code>napi_open_escapable_handle_scope</code></a> and 1564 <a href="#n_api_napi_close_escapable_handle_scope"><code>napi_close_escapable_handle_scope</code></a>.</p> 1565 <p>The request to promote a handle is made through <a href="#n_api_napi_escape_handle"><code>napi_escape_handle</code></a> which 1566 can only be called once.</p> 1567 <h5>napi_open_handle_scope<span><a class="mark" href="#n_api_napi_open_handle_scope" id="n_api_napi_open_handle_scope">#</a></span></h5> 1568 <div class="api_metadata"> 1569 <span>Added in: v8.0.0</span> 1570 <span>N-API version: 1</span> 1571 </div> 1572 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_open_handle_scope</span><span class="hljs-params">(napi_env env, 1573 napi_handle_scope* result)</span>;</code></pre> 1574 <ul> 1575 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1576 <li><code>[out] result</code>: <code>napi_value</code> representing the new scope.</li> 1577 </ul> 1578 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1579 <p>This API opens a new scope.</p> 1580 <h5>napi_close_handle_scope<span><a class="mark" href="#n_api_napi_close_handle_scope" id="n_api_napi_close_handle_scope">#</a></span></h5> 1581 <div class="api_metadata"> 1582 <span>Added in: v8.0.0</span> 1583 <span>N-API version: 1</span> 1584 </div> 1585 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_close_handle_scope</span><span class="hljs-params">(napi_env env, 1586 napi_handle_scope scope)</span>;</code></pre> 1587 <ul> 1588 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1589 <li><code>[in] scope</code>: <code>napi_value</code> representing the scope to be closed.</li> 1590 </ul> 1591 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1592 <p>This API closes the scope passed in. Scopes must be closed in the 1593 reverse order from which they were created.</p> 1594 <p>This API can be called even if there is a pending JavaScript exception.</p> 1595 <h5>napi_open_escapable_handle_scope<span><a class="mark" href="#n_api_napi_open_escapable_handle_scope" id="n_api_napi_open_escapable_handle_scope">#</a></span></h5> 1596 <div class="api_metadata"> 1597 <span>Added in: v8.0.0</span> 1598 <span>N-API version: 1</span> 1599 </div> 1600 <pre><code class="language-c">NAPI_EXTERN napi_status 1601 <span class="hljs-title function_">napi_open_escapable_handle_scope</span><span class="hljs-params">(napi_env env, 1602 napi_handle_scope* result)</span>;</code></pre> 1603 <ul> 1604 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1605 <li><code>[out] result</code>: <code>napi_value</code> representing the new scope.</li> 1606 </ul> 1607 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1608 <p>This API opens a new scope from which one object can be promoted 1609 to the outer scope.</p> 1610 <h5>napi_close_escapable_handle_scope<span><a class="mark" href="#n_api_napi_close_escapable_handle_scope" id="n_api_napi_close_escapable_handle_scope">#</a></span></h5> 1611 <div class="api_metadata"> 1612 <span>Added in: v8.0.0</span> 1613 <span>N-API version: 1</span> 1614 </div> 1615 <pre><code class="language-c">NAPI_EXTERN napi_status 1616 <span class="hljs-title function_">napi_close_escapable_handle_scope</span><span class="hljs-params">(napi_env env, 1617 napi_handle_scope scope)</span>;</code></pre> 1618 <ul> 1619 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1620 <li><code>[in] scope</code>: <code>napi_value</code> representing the scope to be closed.</li> 1621 </ul> 1622 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1623 <p>This API closes the scope passed in. Scopes must be closed in the 1624 reverse order from which they were created.</p> 1625 <p>This API can be called even if there is a pending JavaScript exception.</p> 1626 <h5>napi_escape_handle<span><a class="mark" href="#n_api_napi_escape_handle" id="n_api_napi_escape_handle">#</a></span></h5> 1627 <div class="api_metadata"> 1628 <span>Added in: v8.0.0</span> 1629 <span>N-API version: 1</span> 1630 </div> 1631 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_escape_handle</span><span class="hljs-params">(napi_env env, 1632 napi_escapable_handle_scope scope, 1633 napi_value escapee, 1634 napi_value* result)</span>;</code></pre> 1635 <ul> 1636 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1637 <li><code>[in] scope</code>: <code>napi_value</code> representing the current scope.</li> 1638 <li><code>[in] escapee</code>: <code>napi_value</code> representing the JavaScript <code>Object</code> to be 1639 escaped.</li> 1640 <li><code>[out] result</code>: <code>napi_value</code> representing the handle to the escaped <code>Object</code> 1641 in the outer scope.</li> 1642 </ul> 1643 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1644 <p>This API promotes the handle to the JavaScript object so that it is valid 1645 for the lifetime of the outer scope. It can only be called once per scope. 1646 If it is called more than once an error will be returned.</p> 1647 <p>This API can be called even if there is a pending JavaScript exception.</p> 1648 <h4>References to objects with a lifespan longer than that of the native method<span><a class="mark" href="#n_api_references_to_objects_with_a_lifespan_longer_than_that_of_the_native_method" id="n_api_references_to_objects_with_a_lifespan_longer_than_that_of_the_native_method">#</a></span></h4> 1649 <p>In some cases an addon will need to be able to create and reference objects 1650 with a lifespan longer than that of a single native method invocation. For 1651 example, to create a constructor and later use that constructor 1652 in a request to creates instances, it must be possible to reference 1653 the constructor object across many different instance creation requests. This 1654 would not be possible with a normal handle returned as a <code>napi_value</code> as 1655 described in the earlier section. The lifespan of a normal handle is 1656 managed by scopes and all scopes must be closed before the end of a native 1657 method.</p> 1658 <p>Node-API provides methods to create persistent references to an object. 1659 Each persistent reference has an associated count with a value of 0 1660 or higher. The count determines if the reference will keep 1661 the corresponding object live. References with a count of 0 do not 1662 prevent the object from being collected and are often called 'weak' 1663 references. Any count greater than 0 will prevent the object 1664 from being collected.</p> 1665 <p>References can be created with an initial reference count. The count can 1666 then be modified through <a href="#n_api_napi_reference_ref"><code>napi_reference_ref</code></a> and 1667 <a href="#n_api_napi_reference_unref"><code>napi_reference_unref</code></a>. If an object is collected while the count 1668 for a reference is 0, all subsequent calls to 1669 get the object associated with the reference <a href="#n_api_napi_get_reference_value"><code>napi_get_reference_value</code></a> 1670 will return <code>NULL</code> for the returned <code>napi_value</code>. An attempt to call 1671 <a href="#n_api_napi_reference_ref"><code>napi_reference_ref</code></a> for a reference whose object has been collected 1672 results in an error.</p> 1673 <p>References must be deleted once they are no longer required by the addon. When 1674 a reference is deleted, it will no longer prevent the corresponding object from 1675 being collected. Failure to delete a persistent reference results in 1676 a 'memory leak' with both the native memory for the persistent reference and 1677 the corresponding object on the heap being retained forever.</p> 1678 <p>There can be multiple persistent references created which refer to the same 1679 object, each of which will either keep the object live or not based on its 1680 individual count.</p> 1681 <h5>napi_create_reference<span><a class="mark" href="#n_api_napi_create_reference" id="n_api_napi_create_reference">#</a></span></h5> 1682 <div class="api_metadata"> 1683 <span>Added in: v8.0.0</span> 1684 <span>N-API version: 1</span> 1685 </div> 1686 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_create_reference</span><span class="hljs-params">(napi_env env, 1687 napi_value value, 1688 <span class="hljs-type">uint32_t</span> initial_refcount, 1689 napi_ref* result)</span>;</code></pre> 1690 <ul> 1691 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1692 <li><code>[in] value</code>: <code>napi_value</code> representing the <code>Object</code> to which we want a 1693 reference.</li> 1694 <li><code>[in] initial_refcount</code>: Initial reference count for the new reference.</li> 1695 <li><code>[out] result</code>: <code>napi_ref</code> pointing to the new reference.</li> 1696 </ul> 1697 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1698 <p>This API create a new reference with the specified reference count 1699 to the <code>Object</code> passed in.</p> 1700 <h5>napi_delete_reference<span><a class="mark" href="#n_api_napi_delete_reference" id="n_api_napi_delete_reference">#</a></span></h5> 1701 <div class="api_metadata"> 1702 <span>Added in: v8.0.0</span> 1703 <span>N-API version: 1</span> 1704 </div> 1705 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_delete_reference</span><span class="hljs-params">(napi_env env, napi_ref ref)</span>;</code></pre> 1706 <ul> 1707 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1708 <li><code>[in] ref</code>: <code>napi_ref</code> to be deleted.</li> 1709 </ul> 1710 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1711 <p>This API deletes the reference passed in.</p> 1712 <p>This API can be called even if there is a pending JavaScript exception.</p> 1713 <h5>napi_reference_ref<span><a class="mark" href="#n_api_napi_reference_ref" id="n_api_napi_reference_ref">#</a></span></h5> 1714 <div class="api_metadata"> 1715 <span>Added in: v8.0.0</span> 1716 <span>N-API version: 1</span> 1717 </div> 1718 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_reference_ref</span><span class="hljs-params">(napi_env env, 1719 napi_ref ref, 1720 <span class="hljs-type">uint32_t</span>* result)</span>;</code></pre> 1721 <ul> 1722 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1723 <li><code>[in] ref</code>: <code>napi_ref</code> for which the reference count will be incremented.</li> 1724 <li><code>[out] result</code>: The new reference count.</li> 1725 </ul> 1726 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1727 <p>This API increments the reference count for the reference 1728 passed in and returns the resulting reference count.</p> 1729 <h5>napi_reference_unref<span><a class="mark" href="#n_api_napi_reference_unref" id="n_api_napi_reference_unref">#</a></span></h5> 1730 <div class="api_metadata"> 1731 <span>Added in: v8.0.0</span> 1732 <span>N-API version: 1</span> 1733 </div> 1734 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_reference_unref</span><span class="hljs-params">(napi_env env, 1735 napi_ref ref, 1736 <span class="hljs-type">uint32_t</span>* result)</span>;</code></pre> 1737 <ul> 1738 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1739 <li><code>[in] ref</code>: <code>napi_ref</code> for which the reference count will be decremented.</li> 1740 <li><code>[out] result</code>: The new reference count.</li> 1741 </ul> 1742 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1743 <p>This API decrements the reference count for the reference 1744 passed in and returns the resulting reference count.</p> 1745 <h5>napi_get_reference_value<span><a class="mark" href="#n_api_napi_get_reference_value" id="n_api_napi_get_reference_value">#</a></span></h5> 1746 <div class="api_metadata"> 1747 <span>Added in: v8.0.0</span> 1748 <span>N-API version: 1</span> 1749 </div> 1750 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_get_reference_value</span><span class="hljs-params">(napi_env env, 1751 napi_ref ref, 1752 napi_value* result)</span>;</code></pre> 1753 <p>the <code>napi_value passed</code> in or out of these methods is a handle to the 1754 object to which the reference is related.</p> 1755 <ul> 1756 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1757 <li><code>[in] ref</code>: <code>napi_ref</code> for which we requesting the corresponding <code>Object</code>.</li> 1758 <li><code>[out] result</code>: The <code>napi_value</code> for the <code>Object</code> referenced by the 1759 <code>napi_ref</code>.</li> 1760 </ul> 1761 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 1762 <p>If still valid, this API returns the <code>napi_value</code> representing the 1763 JavaScript <code>Object</code> associated with the <code>napi_ref</code>. Otherwise, result 1764 will be <code>NULL</code>.</p> 1765 <h4>Cleanup on exit of the current Node.js instance<span><a class="mark" href="#n_api_cleanup_on_exit_of_the_current_node_js_instance" id="n_api_cleanup_on_exit_of_the_current_node_js_instance">#</a></span></h4> 1766 <p>While a Node.js process typically releases all its resources when exiting, 1767 embedders of Node.js, or future Worker support, may require addons to register 1768 clean-up hooks that will be run once the current Node.js instance exits.</p> 1769 <p>Node-API provides functions for registering and un-registering such callbacks. 1770 When those callbacks are run, all resources that are being held by the addon 1771 should be freed up.</p> 1772 <h5>napi_add_env_cleanup_hook<span><a class="mark" href="#n_api_napi_add_env_cleanup_hook" id="n_api_napi_add_env_cleanup_hook">#</a></span></h5> 1773 <div class="api_metadata"> 1774 <span>Added in: v10.2.0</span> 1775 <span>N-API version: 3</span> 1776 </div> 1777 <pre><code class="language-c">NODE_EXTERN napi_status <span class="hljs-title function_">napi_add_env_cleanup_hook</span><span class="hljs-params">(napi_env env, 1778 <span class="hljs-type">void</span> (*fun)(<span class="hljs-type">void</span>* arg), 1779 <span class="hljs-type">void</span>* arg)</span>;</code></pre> 1780 <p>Registers <code>fun</code> as a function to be run with the <code>arg</code> parameter once the 1781 current Node.js environment exits.</p> 1782 <p>A function can safely be specified multiple times with different 1783 <code>arg</code> values. In that case, it will be called multiple times as well. 1784 Providing the same <code>fun</code> and <code>arg</code> values multiple times is not allowed 1785 and will lead the process to abort.</p> 1786 <p>The hooks will be called in reverse order, i.e. the most recently added one 1787 will be called first.</p> 1788 <p>Removing this hook can be done by using <a href="#n_api_napi_remove_env_cleanup_hook"><code>napi_remove_env_cleanup_hook</code></a>. 1789 Typically, that happens when the resource for which this hook was added 1790 is being torn down anyway.</p> 1791 <p>For asynchronous cleanup, <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a> is available.</p> 1792 <h5>napi_remove_env_cleanup_hook<span><a class="mark" href="#n_api_napi_remove_env_cleanup_hook" id="n_api_napi_remove_env_cleanup_hook">#</a></span></h5> 1793 <div class="api_metadata"> 1794 <span>Added in: v10.2.0</span> 1795 <span>N-API version: 3</span> 1796 </div> 1797 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_remove_env_cleanup_hook</span><span class="hljs-params">(napi_env env, 1798 <span class="hljs-type">void</span> (*fun)(<span class="hljs-type">void</span>* arg), 1799 <span class="hljs-type">void</span>* arg)</span>;</code></pre> 1800 <p>Unregisters <code>fun</code> as a function to be run with the <code>arg</code> parameter once the 1801 current Node.js environment exits. Both the argument and the function value 1802 need to be exact matches.</p> 1803 <p>The function must have originally been registered 1804 with <code>napi_add_env_cleanup_hook</code>, otherwise the process will abort.</p> 1805 <h5>napi_add_async_cleanup_hook<span><a class="mark" href="#n_api_napi_add_async_cleanup_hook" id="n_api_napi_add_async_cleanup_hook">#</a></span></h5> 1806 <div class="api_metadata"> 1807 <details class="changelog"><summary>History</summary> 1808 <table> 1809 <tbody><tr><th>Version</th><th>Changes</th></tr> 1810 <tr><td>v14.10.0</td> 1811 <td><p>Changed signature of the <code>hook</code> callback.</p></td></tr> 1812 <tr><td>v14.8.0, v12.19.0</td> 1813 <td><p><span>Added in: v14.8.0, v12.19.0</span></p></td></tr> 1814 </tbody></table> 1815 </details> 1816 <span>N-API version: 8</span> 1817 </div> 1818 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_add_async_cleanup_hook</span><span class="hljs-params">( 1819 napi_env env, 1820 napi_async_cleanup_hook hook, 1821 <span class="hljs-type">void</span>* arg, 1822 napi_async_cleanup_hook_handle* remove_handle)</span>;</code></pre> 1823 <ul> 1824 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 1825 <li><code>[in] hook</code>: The function pointer to call at environment teardown.</li> 1826 <li><code>[in] arg</code>: The pointer to pass to <code>hook</code> when it gets called.</li> 1827 <li><code>[out] remove_handle</code>: Optional handle that refers to the asynchronous cleanup 1828 hook.</li> 1829 </ul> 1830 <p>Registers <code>hook</code>, which is a function of type <a href="#n_api_napi_async_cleanup_hook"><code>napi_async_cleanup_hook</code></a>, as 1831 a function to be run with the <code>remove_handle</code> and <code>arg</code> parameters once the 1832 current Node.js environment exits.</p> 1833 <p>Unlike <a href="#n_api_napi_add_env_cleanup_hook"><code>napi_add_env_cleanup_hook</code></a>, the hook is allowed to be asynchronous.</p> 1834 <p>Otherwise, behavior generally matches that of <a href="#n_api_napi_add_env_cleanup_hook"><code>napi_add_env_cleanup_hook</code></a>.</p> 1835 <p>If <code>remove_handle</code> is not <code>NULL</code>, an opaque value will be stored in it 1836 that must later be passed to <a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a>, 1837 regardless of whether the hook has already been invoked. 1838 Typically, that happens when the resource for which this hook was added 1839 is being torn down anyway.</p> 1840 <h5>napi_remove_async_cleanup_hook<span><a class="mark" href="#n_api_napi_remove_async_cleanup_hook" id="n_api_napi_remove_async_cleanup_hook">#</a></span></h5> 1841 <div class="api_metadata"> 1842 <details class="changelog"><summary>History</summary> 1843 <table> 1844 <tbody><tr><th>Version</th><th>Changes</th></tr> 1845 <tr><td>v14.10.0</td> 1846 <td><p>Removed <code>env</code> parameter.</p></td></tr> 1847 <tr><td>v14.8.0</td> 1848 <td><p><span>Added in: v14.8.0</span></p></td></tr> 1849 </tbody></table> 1850 </details> 1851 </div> 1852 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_remove_async_cleanup_hook</span><span class="hljs-params">( 1853 napi_async_cleanup_hook_handle remove_handle)</span>;</code></pre> 1854 <ul> 1855 <li><code>[in] remove_handle</code>: The handle to an asynchronous cleanup hook that was 1856 created with <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a>.</li> 1857 </ul> 1858 <p>Unregisters the cleanup hook corresponding to <code>remove_handle</code>. This will prevent 1859 the hook from being executed, unless it has already started executing. 1860 This must be called on any <code>napi_async_cleanup_hook_handle</code> value obtained 1861 from <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a>.</p> 1862 </section><section><h3>Module registration<span><a class="mark" href="#n_api_module_registration" id="n_api_module_registration">#</a></span></h3> 1863 <p>Node-API modules are registered in a manner similar to other modules 1864 except that instead of using the <code>NODE_MODULE</code> macro the following 1865 is used:</p> 1866 <pre><code class="language-c">NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)</code></pre> 1867 <p>The next difference is the signature for the <code>Init</code> method. For a Node-API 1868 module it is as follows:</p> 1869 <pre><code class="language-c">napi_value <span class="hljs-title function_">Init</span><span class="hljs-params">(napi_env env, napi_value exports)</span>;</code></pre> 1870 <p>The return value from <code>Init</code> is treated as the <code>exports</code> object for the module. 1871 The <code>Init</code> method is passed an empty object via the <code>exports</code> parameter as a 1872 convenience. If <code>Init</code> returns <code>NULL</code>, the parameter passed as <code>exports</code> is 1873 exported by the module. Node-API modules cannot modify the <code>module</code> object but 1874 can specify anything as the <code>exports</code> property of the module.</p> 1875 <p>To add the method <code>hello</code> as a function so that it can be called as a method 1876 provided by the addon:</p> 1877 <pre><code class="language-c">napi_value <span class="hljs-title function_">Init</span><span class="hljs-params">(napi_env env, napi_value exports)</span> { 1878 napi_status status; 1879 napi_property_descriptor desc = { 1880 <span class="hljs-string">"hello"</span>, 1881 <span class="hljs-literal">NULL</span>, 1882 Method, 1883 <span class="hljs-literal">NULL</span>, 1884 <span class="hljs-literal">NULL</span>, 1885 <span class="hljs-literal">NULL</span>, 1886 napi_writable | napi_enumerable | napi_configurable, 1887 <span class="hljs-literal">NULL</span> 1888 }; 1889 status = napi_define_properties(env, exports, <span class="hljs-number">1</span>, &desc); 1890 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1891 <span class="hljs-keyword">return</span> exports; 1892 }</code></pre> 1893 <p>To set a function to be returned by the <code>require()</code> for the addon:</p> 1894 <pre><code class="language-c">napi_value <span class="hljs-title function_">Init</span><span class="hljs-params">(napi_env env, napi_value exports)</span> { 1895 napi_value method; 1896 napi_status status; 1897 status = napi_create_function(env, <span class="hljs-string">"exports"</span>, NAPI_AUTO_LENGTH, Method, <span class="hljs-literal">NULL</span>, &method); 1898 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1899 <span class="hljs-keyword">return</span> method; 1900 }</code></pre> 1901 <p>To define a class so that new instances can be created (often used with 1902 <a href="#n_api_object_wrap">Object wrap</a>):</p> 1903 <pre><code class="language-c"><span class="hljs-comment">// <span class="hljs-doctag">NOTE:</span> partial example, not all referenced code is included</span> 1904 napi_value <span class="hljs-title function_">Init</span><span class="hljs-params">(napi_env env, napi_value exports)</span> { 1905 napi_status status; 1906 napi_property_descriptor properties[] = { 1907 { <span class="hljs-string">"value"</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, GetValue, SetValue, <span class="hljs-literal">NULL</span>, napi_writable | napi_configurable, <span class="hljs-literal">NULL</span> }, 1908 DECLARE_NAPI_METHOD(<span class="hljs-string">"plusOne"</span>, PlusOne), 1909 DECLARE_NAPI_METHOD(<span class="hljs-string">"multiply"</span>, Multiply), 1910 }; 1911 1912 napi_value cons; 1913 status = 1914 napi_define_class(env, <span class="hljs-string">"MyObject"</span>, New, <span class="hljs-literal">NULL</span>, <span class="hljs-number">3</span>, properties, &cons); 1915 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1916 1917 status = napi_create_reference(env, cons, <span class="hljs-number">1</span>, &constructor); 1918 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1919 1920 status = napi_set_named_property(env, exports, <span class="hljs-string">"MyObject"</span>, cons); 1921 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1922 1923 <span class="hljs-keyword">return</span> exports; 1924 }</code></pre> 1925 <p>You can also use the <code>NAPI_MODULE_INIT</code> macro, which acts as a shorthand 1926 for <code>NAPI_MODULE</code> and defining an <code>Init</code> function:</p> 1927 <pre><code class="language-c">NAPI_MODULE_INIT() { 1928 napi_value answer; 1929 napi_status result; 1930 1931 status = napi_create_int64(env, <span class="hljs-number">42</span>, &answer); 1932 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1933 1934 status = napi_set_named_property(env, exports, <span class="hljs-string">"answer"</span>, answer); 1935 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1936 1937 <span class="hljs-keyword">return</span> exports; 1938 }</code></pre> 1939 <p>All Node-API addons are context-aware, meaning they may be loaded multiple 1940 times. There are a few design considerations when declaring such a module. 1941 The documentation on <a href="addons.html#addons_context_aware_addons">context-aware addons</a> provides more details.</p> 1942 <p>The variables <code>env</code> and <code>exports</code> will be available inside the function body 1943 following the macro invocation.</p> 1944 <p>For more details on setting properties on objects, see the section on 1945 <a href="#n_api_working_with_javascript_properties">Working with JavaScript properties</a>.</p> 1946 <p>For more details on building addon modules in general, refer to the existing 1947 API.</p> 1948 </section><section><h3>Working with JavaScript values<span><a class="mark" href="#n_api_working_with_javascript_values" id="n_api_working_with_javascript_values">#</a></span></h3> 1949 <p>Node-API exposes a set of APIs to create all types of JavaScript values. 1950 Some of these types are documented under <a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Section 6</a> 1951 of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</p> 1952 <p>Fundamentally, these APIs are used to do one of the following:</p> 1953 <ol> 1954 <li>Create a new JavaScript object</li> 1955 <li>Convert from a primitive C type to a Node-API value</li> 1956 <li>Convert from Node-API value to a primitive C type</li> 1957 <li>Get global instances including <code>undefined</code> and <code>null</code></li> 1958 </ol> 1959 <p>Node-API values are represented by the type <code>napi_value</code>. 1960 Any Node-API call that requires a JavaScript value takes in a <code>napi_value</code>. 1961 In some cases, the API does check the type of the <code>napi_value</code> up-front. 1962 However, for better performance, it's better for the caller to make sure that 1963 the <code>napi_value</code> in question is of the JavaScript type expected by the API.</p> 1964 <h4>Enum types<span><a class="mark" href="#n_api_enum_types" id="n_api_enum_types">#</a></span></h4> 1965 <h5>napi_key_collection_mode<span><a class="mark" href="#n_api_napi_key_collection_mode" id="n_api_napi_key_collection_mode">#</a></span></h5> 1966 <div class="api_metadata"> 1967 <span>Added in: v13.7.0, v10.20.0</span> 1968 <span>N-API version: 6</span> 1969 </div> 1970 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 1971 napi_key_include_prototypes, 1972 napi_key_own_only 1973 } napi_key_collection_mode;</code></pre> 1974 <p>Describes the <code>Keys/Properties</code> filter enums:</p> 1975 <p><code>napi_key_collection_mode</code> limits the range of collected properties.</p> 1976 <p><code>napi_key_own_only</code> limits the collected properties to the given 1977 object only. <code>napi_key_include_prototypes</code> will include all keys 1978 of the objects's prototype chain as well.</p> 1979 <h5>napi_key_filter<span><a class="mark" href="#n_api_napi_key_filter" id="n_api_napi_key_filter">#</a></span></h5> 1980 <div class="api_metadata"> 1981 <span>Added in: v13.7.0, v10.20.0</span> 1982 <span>N-API version: 6</span> 1983 </div> 1984 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 1985 napi_key_all_properties = <span class="hljs-number">0</span>, 1986 napi_key_writable = <span class="hljs-number">1</span>, 1987 napi_key_enumerable = <span class="hljs-number">1</span> << <span class="hljs-number">1</span>, 1988 napi_key_configurable = <span class="hljs-number">1</span> << <span class="hljs-number">2</span>, 1989 napi_key_skip_strings = <span class="hljs-number">1</span> << <span class="hljs-number">3</span>, 1990 napi_key_skip_symbols = <span class="hljs-number">1</span> << <span class="hljs-number">4</span> 1991 } napi_key_filter;</code></pre> 1992 <p>Property filter bits. They can be or'ed to build a composite filter.</p> 1993 <h5>napi_key_conversion<span><a class="mark" href="#n_api_napi_key_conversion" id="n_api_napi_key_conversion">#</a></span></h5> 1994 <div class="api_metadata"> 1995 <span>Added in: v13.7.0, v10.20.0</span> 1996 <span>N-API version: 6</span> 1997 </div> 1998 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 1999 napi_key_keep_numbers, 2000 napi_key_numbers_to_strings 2001 } napi_key_conversion;</code></pre> 2002 <p><code>napi_key_numbers_to_strings</code> will convert integer indices to 2003 strings. <code>napi_key_keep_numbers</code> will return numbers for integer 2004 indices.</p> 2005 <h5>napi_valuetype<span><a class="mark" href="#n_api_napi_valuetype" id="n_api_napi_valuetype">#</a></span></h5> 2006 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 2007 <span class="hljs-comment">// ES6 types (corresponds to typeof)</span> 2008 napi_undefined, 2009 napi_null, 2010 napi_boolean, 2011 napi_number, 2012 napi_string, 2013 napi_symbol, 2014 napi_object, 2015 napi_function, 2016 napi_external, 2017 napi_bigint, 2018 } napi_valuetype;</code></pre> 2019 <p>Describes the type of a <code>napi_value</code>. This generally corresponds to the types 2020 described in <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">Section 6.1</a> of the ECMAScript Language Specification. 2021 In addition to types in that section, <code>napi_valuetype</code> can also represent 2022 <code>Function</code>s and <code>Object</code>s with external data.</p> 2023 <p>A JavaScript value of type <code>napi_external</code> appears in JavaScript as a plain 2024 object such that no properties can be set on it, and no prototype.</p> 2025 <h5>napi_typedarray_type<span><a class="mark" href="#n_api_napi_typedarray_type" id="n_api_napi_typedarray_type">#</a></span></h5> 2026 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 2027 napi_int8_array, 2028 napi_uint8_array, 2029 napi_uint8_clamped_array, 2030 napi_int16_array, 2031 napi_uint16_array, 2032 napi_int32_array, 2033 napi_uint32_array, 2034 napi_float32_array, 2035 napi_float64_array, 2036 napi_bigint64_array, 2037 napi_biguint64_array, 2038 } napi_typedarray_type;</code></pre> 2039 <p>This represents the underlying binary scalar datatype of the <code>TypedArray</code>. 2040 Elements of this enum correspond to 2041 <a href="https://tc39.github.io/ecma262/#sec-typedarray-objects">Section 22.2</a> of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</p> 2042 <h4>Object creation functions<span><a class="mark" href="#n_api_object_creation_functions" id="n_api_object_creation_functions">#</a></span></h4> 2043 <h5>napi_create_array<span><a class="mark" href="#n_api_napi_create_array" id="n_api_napi_create_array">#</a></span></h5> 2044 <div class="api_metadata"> 2045 <span>Added in: v8.0.0</span> 2046 <span>N-API version: 1</span> 2047 </div> 2048 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_array</span><span class="hljs-params">(napi_env env, napi_value* result)</span></code></pre> 2049 <ul> 2050 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 2051 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Array</code>.</li> 2052 </ul> 2053 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2054 <p>This API returns a Node-API value corresponding to a JavaScript <code>Array</code> type. 2055 JavaScript arrays are described in 2056 <a href="https://tc39.github.io/ecma262/#sec-array-objects">Section 22.1</a> of the ECMAScript Language Specification.</p> 2057 <h5>napi_create_array_with_length<span><a class="mark" href="#n_api_napi_create_array_with_length" id="n_api_napi_create_array_with_length">#</a></span></h5> 2058 <div class="api_metadata"> 2059 <span>Added in: v8.0.0</span> 2060 <span>N-API version: 1</span> 2061 </div> 2062 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_array_with_length</span><span class="hljs-params">(napi_env env, 2063 <span class="hljs-type">size_t</span> length, 2064 napi_value* result)</span></code></pre> 2065 <ul> 2066 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2067 <li><code>[in] length</code>: The initial length of the <code>Array</code>.</li> 2068 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Array</code>.</li> 2069 </ul> 2070 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2071 <p>This API returns a Node-API value corresponding to a JavaScript <code>Array</code> type. 2072 The <code>Array</code>'s length property is set to the passed-in length parameter. 2073 However, the underlying buffer is not guaranteed to be pre-allocated by the VM 2074 when the array is created. That behavior is left to the underlying VM 2075 implementation. If the buffer must be a contiguous block of memory that can be 2076 directly read and/or written via C, consider using 2077 <a href="#n_api_napi_create_external_arraybuffer"><code>napi_create_external_arraybuffer</code></a>.</p> 2078 <p>JavaScript arrays are described in 2079 <a href="https://tc39.github.io/ecma262/#sec-array-objects">Section 22.1</a> of the ECMAScript Language Specification.</p> 2080 <h5>napi_create_arraybuffer<span><a class="mark" href="#n_api_napi_create_arraybuffer" id="n_api_napi_create_arraybuffer">#</a></span></h5> 2081 <div class="api_metadata"> 2082 <span>Added in: v8.0.0</span> 2083 <span>N-API version: 1</span> 2084 </div> 2085 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_arraybuffer</span><span class="hljs-params">(napi_env env, 2086 <span class="hljs-type">size_t</span> byte_length, 2087 <span class="hljs-type">void</span>** data, 2088 napi_value* result)</span></code></pre> 2089 <ul> 2090 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2091 <li><code>[in] length</code>: The length in bytes of the array buffer to create.</li> 2092 <li><code>[out] data</code>: Pointer to the underlying byte buffer of the <code>ArrayBuffer</code>.</li> 2093 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>ArrayBuffer</code>.</li> 2094 </ul> 2095 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2096 <p>This API returns a Node-API value corresponding to a JavaScript <code>ArrayBuffer</code>. 2097 <code>ArrayBuffer</code>s are used to represent fixed-length binary data buffers. They are 2098 normally used as a backing-buffer for <code>TypedArray</code> objects. 2099 The <code>ArrayBuffer</code> allocated will have an underlying byte buffer whose size is 2100 determined by the <code>length</code> parameter that's passed in. 2101 The underlying buffer is optionally returned back to the caller in case the 2102 caller wants to directly manipulate the buffer. This buffer can only be 2103 written to directly from native code. To write to this buffer from JavaScript, 2104 a typed array or <code>DataView</code> object would need to be created.</p> 2105 <p>JavaScript <code>ArrayBuffer</code> objects are described in 2106 <a href="https://tc39.github.io/ecma262/#sec-arraybuffer-objects">Section 24.1</a> of the ECMAScript Language Specification.</p> 2107 <h5>napi_create_buffer<span><a class="mark" href="#n_api_napi_create_buffer" id="n_api_napi_create_buffer">#</a></span></h5> 2108 <div class="api_metadata"> 2109 <span>Added in: v8.0.0</span> 2110 <span>N-API version: 1</span> 2111 </div> 2112 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_buffer</span><span class="hljs-params">(napi_env env, 2113 <span class="hljs-type">size_t</span> size, 2114 <span class="hljs-type">void</span>** data, 2115 napi_value* result)</span></code></pre> 2116 <ul> 2117 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2118 <li><code>[in] size</code>: Size in bytes of the underlying buffer.</li> 2119 <li><code>[out] data</code>: Raw pointer to the underlying buffer.</li> 2120 <li><code>[out] result</code>: A <code>napi_value</code> representing a <code>node::Buffer</code>.</li> 2121 </ul> 2122 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2123 <p>This API allocates a <code>node::Buffer</code> object. While this is still a 2124 fully-supported data structure, in most cases using a <code>TypedArray</code> will suffice.</p> 2125 <h5>napi_create_buffer_copy<span><a class="mark" href="#n_api_napi_create_buffer_copy" id="n_api_napi_create_buffer_copy">#</a></span></h5> 2126 <div class="api_metadata"> 2127 <span>Added in: v8.0.0</span> 2128 <span>N-API version: 1</span> 2129 </div> 2130 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_buffer_copy</span><span class="hljs-params">(napi_env env, 2131 <span class="hljs-type">size_t</span> length, 2132 <span class="hljs-keyword">const</span> <span class="hljs-type">void</span>* data, 2133 <span class="hljs-type">void</span>** result_data, 2134 napi_value* result)</span></code></pre> 2135 <ul> 2136 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2137 <li><code>[in] size</code>: Size in bytes of the input buffer (should be the same as the size 2138 of the new buffer).</li> 2139 <li><code>[in] data</code>: Raw pointer to the underlying buffer to copy from.</li> 2140 <li><code>[out] result_data</code>: Pointer to the new <code>Buffer</code>'s underlying data buffer.</li> 2141 <li><code>[out] result</code>: A <code>napi_value</code> representing a <code>node::Buffer</code>.</li> 2142 </ul> 2143 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2144 <p>This API allocates a <code>node::Buffer</code> object and initializes it with data copied 2145 from the passed-in buffer. While this is still a fully-supported data 2146 structure, in most cases using a <code>TypedArray</code> will suffice.</p> 2147 <h5>napi_create_date<span><a class="mark" href="#n_api_napi_create_date" id="n_api_napi_create_date">#</a></span></h5> 2148 <div class="api_metadata"> 2149 <span>Added in: v11.11.0, v10.17.0</span> 2150 <span>N-API version: 5</span> 2151 </div> 2152 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_date</span><span class="hljs-params">(napi_env env, 2153 <span class="hljs-type">double</span> time, 2154 napi_value* result)</span>;</code></pre> 2155 <ul> 2156 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2157 <li><code>[in] time</code>: ECMAScript time value in milliseconds since 01 January, 1970 UTC.</li> 2158 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Date</code>.</li> 2159 </ul> 2160 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2161 <p>This API does not observe leap seconds; they are ignored, as 2162 ECMAScript aligns with POSIX time specification.</p> 2163 <p>This API allocates a JavaScript <code>Date</code> object.</p> 2164 <p>JavaScript <code>Date</code> objects are described in 2165 <a href="https://tc39.github.io/ecma262/#sec-date-objects">Section 20.3</a> of the ECMAScript Language Specification.</p> 2166 <h5>napi_create_external<span><a class="mark" href="#n_api_napi_create_external" id="n_api_napi_create_external">#</a></span></h5> 2167 <div class="api_metadata"> 2168 <span>Added in: v8.0.0</span> 2169 <span>N-API version: 1</span> 2170 </div> 2171 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_external</span><span class="hljs-params">(napi_env env, 2172 <span class="hljs-type">void</span>* data, 2173 napi_finalize finalize_cb, 2174 <span class="hljs-type">void</span>* finalize_hint, 2175 napi_value* result)</span></code></pre> 2176 <ul> 2177 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2178 <li><code>[in] data</code>: Raw pointer to the external data.</li> 2179 <li><code>[in] finalize_cb</code>: Optional callback to call when the external value is being 2180 collected. <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 2181 <li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 2182 collection.</li> 2183 <li><code>[out] result</code>: A <code>napi_value</code> representing an external value.</li> 2184 </ul> 2185 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2186 <p>This API allocates a JavaScript value with external data attached to it. This 2187 is used to pass external data through JavaScript code, so it can be retrieved 2188 later by native code using <a href="#n_api_napi_get_value_external"><code>napi_get_value_external</code></a>.</p> 2189 <p>The API adds a <code>napi_finalize</code> callback which will be called when the JavaScript 2190 object just created is ready for garbage collection. It is similar to 2191 <code>napi_wrap()</code> except that:</p> 2192 <ul> 2193 <li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 2194 <li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 2195 <li>the object created by the API can be used with <code>napi_wrap()</code>.</li> 2196 </ul> 2197 <p>The created value is not an object, and therefore does not support additional 2198 properties. It is considered a distinct value type: calling <code>napi_typeof()</code> with 2199 an external value yields <code>napi_external</code>.</p> 2200 <h5>napi_create_external_arraybuffer<span><a class="mark" href="#n_api_napi_create_external_arraybuffer" id="n_api_napi_create_external_arraybuffer">#</a></span></h5> 2201 <div class="api_metadata"> 2202 <span>Added in: v8.0.0</span> 2203 <span>N-API version: 1</span> 2204 </div> 2205 <pre><code class="language-c">napi_status 2206 <span class="hljs-title function_">napi_create_external_arraybuffer</span><span class="hljs-params">(napi_env env, 2207 <span class="hljs-type">void</span>* external_data, 2208 <span class="hljs-type">size_t</span> byte_length, 2209 napi_finalize finalize_cb, 2210 <span class="hljs-type">void</span>* finalize_hint, 2211 napi_value* result)</span></code></pre> 2212 <ul> 2213 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2214 <li><code>[in] external_data</code>: Pointer to the underlying byte buffer of the 2215 <code>ArrayBuffer</code>.</li> 2216 <li><code>[in] byte_length</code>: The length in bytes of the underlying buffer.</li> 2217 <li><code>[in] finalize_cb</code>: Optional callback to call when the <code>ArrayBuffer</code> is being 2218 collected. <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 2219 <li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 2220 collection.</li> 2221 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>ArrayBuffer</code>.</li> 2222 </ul> 2223 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2224 <p>This API returns a Node-API value corresponding to a JavaScript <code>ArrayBuffer</code>. 2225 The underlying byte buffer of the <code>ArrayBuffer</code> is externally allocated and 2226 managed. The caller must ensure that the byte buffer remains valid until the 2227 finalize callback is called.</p> 2228 <p>The API adds a <code>napi_finalize</code> callback which will be called when the JavaScript 2229 object just created is ready for garbage collection. It is similar to 2230 <code>napi_wrap()</code> except that:</p> 2231 <ul> 2232 <li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 2233 <li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 2234 <li>the object created by the API can be used with <code>napi_wrap()</code>.</li> 2235 </ul> 2236 <p>JavaScript <code>ArrayBuffer</code>s are described in 2237 <a href="https://tc39.github.io/ecma262/#sec-arraybuffer-objects">Section 24.1</a> of the ECMAScript Language Specification.</p> 2238 <h5>napi_create_external_buffer<span><a class="mark" href="#n_api_napi_create_external_buffer" id="n_api_napi_create_external_buffer">#</a></span></h5> 2239 <div class="api_metadata"> 2240 <span>Added in: v8.0.0</span> 2241 <span>N-API version: 1</span> 2242 </div> 2243 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_external_buffer</span><span class="hljs-params">(napi_env env, 2244 <span class="hljs-type">size_t</span> length, 2245 <span class="hljs-type">void</span>* data, 2246 napi_finalize finalize_cb, 2247 <span class="hljs-type">void</span>* finalize_hint, 2248 napi_value* result)</span></code></pre> 2249 <ul> 2250 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2251 <li><code>[in] length</code>: Size in bytes of the input buffer (should be the same as the 2252 size of the new buffer).</li> 2253 <li><code>[in] data</code>: Raw pointer to the underlying buffer to expose to JavaScript.</li> 2254 <li><code>[in] finalize_cb</code>: Optional callback to call when the <code>ArrayBuffer</code> is being 2255 collected. <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 2256 <li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 2257 collection.</li> 2258 <li><code>[out] result</code>: A <code>napi_value</code> representing a <code>node::Buffer</code>.</li> 2259 </ul> 2260 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2261 <p>This API allocates a <code>node::Buffer</code> object and initializes it with data 2262 backed by the passed in buffer. While this is still a fully-supported data 2263 structure, in most cases using a <code>TypedArray</code> will suffice.</p> 2264 <p>The API adds a <code>napi_finalize</code> callback which will be called when the JavaScript 2265 object just created is ready for garbage collection. It is similar to 2266 <code>napi_wrap()</code> except that:</p> 2267 <ul> 2268 <li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 2269 <li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 2270 <li>the object created by the API can be used with <code>napi_wrap()</code>.</li> 2271 </ul> 2272 <p>For Node.js >=4 <code>Buffers</code> are <code>Uint8Array</code>s.</p> 2273 <h5>napi_create_object<span><a class="mark" href="#n_api_napi_create_object" id="n_api_napi_create_object">#</a></span></h5> 2274 <div class="api_metadata"> 2275 <span>Added in: v8.0.0</span> 2276 <span>N-API version: 1</span> 2277 </div> 2278 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_object</span><span class="hljs-params">(napi_env env, napi_value* result)</span></code></pre> 2279 <ul> 2280 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2281 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Object</code>.</li> 2282 </ul> 2283 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2284 <p>This API allocates a default JavaScript <code>Object</code>. 2285 It is the equivalent of doing <code>new Object()</code> in JavaScript.</p> 2286 <p>The JavaScript <code>Object</code> type is described in <a href="https://tc39.github.io/ecma262/#sec-object-type">Section 6.1.7</a> of the 2287 ECMAScript Language Specification.</p> 2288 <h5>napi_create_symbol<span><a class="mark" href="#n_api_napi_create_symbol" id="n_api_napi_create_symbol">#</a></span></h5> 2289 <div class="api_metadata"> 2290 <span>Added in: v8.0.0</span> 2291 <span>N-API version: 1</span> 2292 </div> 2293 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_symbol</span><span class="hljs-params">(napi_env env, 2294 napi_value description, 2295 napi_value* result)</span></code></pre> 2296 <ul> 2297 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2298 <li><code>[in] description</code>: Optional <code>napi_value</code> which refers to a JavaScript 2299 <code>string</code> to be set as the description for the symbol.</li> 2300 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>symbol</code>.</li> 2301 </ul> 2302 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2303 <p>This API creates a JavaScript <code>symbol</code> value from a UTF8-encoded C string.</p> 2304 <p>The JavaScript <code>symbol</code> type is described in <a href="https://tc39.github.io/ecma262/#sec-symbol-objects">Section 19.4</a> 2305 of the ECMAScript Language Specification.</p> 2306 <h5>napi_create_typedarray<span><a class="mark" href="#n_api_napi_create_typedarray" id="n_api_napi_create_typedarray">#</a></span></h5> 2307 <div class="api_metadata"> 2308 <span>Added in: v8.0.0</span> 2309 <span>N-API version: 1</span> 2310 </div> 2311 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_typedarray</span><span class="hljs-params">(napi_env env, 2312 napi_typedarray_type type, 2313 <span class="hljs-type">size_t</span> length, 2314 napi_value arraybuffer, 2315 <span class="hljs-type">size_t</span> byte_offset, 2316 napi_value* result)</span></code></pre> 2317 <ul> 2318 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2319 <li><code>[in] type</code>: Scalar datatype of the elements within the <code>TypedArray</code>.</li> 2320 <li><code>[in] length</code>: Number of elements in the <code>TypedArray</code>.</li> 2321 <li><code>[in] arraybuffer</code>: <code>ArrayBuffer</code> underlying the typed array.</li> 2322 <li><code>[in] byte_offset</code>: The byte offset within the <code>ArrayBuffer</code> from which to 2323 start projecting the <code>TypedArray</code>.</li> 2324 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>TypedArray</code>.</li> 2325 </ul> 2326 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2327 <p>This API creates a JavaScript <code>TypedArray</code> object over an existing 2328 <code>ArrayBuffer</code>. <code>TypedArray</code> objects provide an array-like view over an 2329 underlying data buffer where each element has the same underlying binary scalar 2330 datatype.</p> 2331 <p>It's required that <code>(length * size_of_element) + byte_offset</code> should 2332 be <= the size in bytes of the array passed in. If not, a <code>RangeError</code> exception 2333 is raised.</p> 2334 <p>JavaScript <code>TypedArray</code> objects are described in 2335 <a href="https://tc39.github.io/ecma262/#sec-typedarray-objects">Section 22.2</a> of the ECMAScript Language Specification.</p> 2336 <h5>napi_create_dataview<span><a class="mark" href="#n_api_napi_create_dataview" id="n_api_napi_create_dataview">#</a></span></h5> 2337 <div class="api_metadata"> 2338 <span>Added in: v8.3.0</span> 2339 <span>N-API version: 1</span> 2340 </div> 2341 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_dataview</span><span class="hljs-params">(napi_env env, 2342 <span class="hljs-type">size_t</span> byte_length, 2343 napi_value arraybuffer, 2344 <span class="hljs-type">size_t</span> byte_offset, 2345 napi_value* result)</span></code></pre> 2346 <ul> 2347 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2348 <li><code>[in] length</code>: Number of elements in the <code>DataView</code>.</li> 2349 <li><code>[in] arraybuffer</code>: <code>ArrayBuffer</code> underlying the <code>DataView</code>.</li> 2350 <li><code>[in] byte_offset</code>: The byte offset within the <code>ArrayBuffer</code> from which to 2351 start projecting the <code>DataView</code>.</li> 2352 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>DataView</code>.</li> 2353 </ul> 2354 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2355 <p>This API creates a JavaScript <code>DataView</code> object over an existing <code>ArrayBuffer</code>. 2356 <code>DataView</code> objects provide an array-like view over an underlying data buffer, 2357 but one which allows items of different size and type in the <code>ArrayBuffer</code>.</p> 2358 <p>It is required that <code>byte_length + byte_offset</code> is less than or equal to the 2359 size in bytes of the array passed in. If not, a <code>RangeError</code> exception is 2360 raised.</p> 2361 <p>JavaScript <code>DataView</code> objects are described in 2362 <a href="https://tc39.github.io/ecma262/#sec-dataview-objects">Section 24.3</a> of the ECMAScript Language Specification.</p> 2363 <h4>Functions to convert from C types to Node-API<span><a class="mark" href="#n_api_functions_to_convert_from_c_types_to_node_api" id="n_api_functions_to_convert_from_c_types_to_node_api">#</a></span></h4> 2364 <h5>napi_create_int32<span><a class="mark" href="#n_api_napi_create_int32" id="n_api_napi_create_int32">#</a></span></h5> 2365 <div class="api_metadata"> 2366 <span>Added in: v8.4.0</span> 2367 <span>N-API version: 1</span> 2368 </div> 2369 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_int32</span><span class="hljs-params">(napi_env env, <span class="hljs-type">int32_t</span> value, napi_value* result)</span></code></pre> 2370 <ul> 2371 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2372 <li><code>[in] value</code>: Integer value to be represented in JavaScript.</li> 2373 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2374 </ul> 2375 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2376 <p>This API is used to convert from the C <code>int32_t</code> type to the JavaScript 2377 <code>number</code> type.</p> 2378 <p>The JavaScript <code>number</code> type is described in 2379 <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type">Section 6.1.6</a> of the ECMAScript Language Specification.</p> 2380 <h5>napi_create_uint32<span><a class="mark" href="#n_api_napi_create_uint32" id="n_api_napi_create_uint32">#</a></span></h5> 2381 <div class="api_metadata"> 2382 <span>Added in: v8.4.0</span> 2383 <span>N-API version: 1</span> 2384 </div> 2385 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_uint32</span><span class="hljs-params">(napi_env env, <span class="hljs-type">uint32_t</span> value, napi_value* result)</span></code></pre> 2386 <ul> 2387 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2388 <li><code>[in] value</code>: Unsigned integer value to be represented in JavaScript.</li> 2389 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2390 </ul> 2391 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2392 <p>This API is used to convert from the C <code>uint32_t</code> type to the JavaScript 2393 <code>number</code> type.</p> 2394 <p>The JavaScript <code>number</code> type is described in 2395 <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type">Section 6.1.6</a> of the ECMAScript Language Specification.</p> 2396 <h5>napi_create_int64<span><a class="mark" href="#n_api_napi_create_int64" id="n_api_napi_create_int64">#</a></span></h5> 2397 <div class="api_metadata"> 2398 <span>Added in: v8.4.0</span> 2399 <span>N-API version: 1</span> 2400 </div> 2401 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_int64</span><span class="hljs-params">(napi_env env, <span class="hljs-type">int64_t</span> value, napi_value* result)</span></code></pre> 2402 <ul> 2403 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2404 <li><code>[in] value</code>: Integer value to be represented in JavaScript.</li> 2405 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2406 </ul> 2407 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2408 <p>This API is used to convert from the C <code>int64_t</code> type to the JavaScript 2409 <code>number</code> type.</p> 2410 <p>The JavaScript <code>number</code> type is described in <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type">Section 6.1.6</a> 2411 of the ECMAScript Language Specification. Note the complete range of <code>int64_t</code> 2412 cannot be represented with full precision in JavaScript. Integer values 2413 outside the range of <a href="https://tc39.github.io/ecma262/#sec-number.min_safe_integer"><code>Number.MIN_SAFE_INTEGER</code></a> <code>-(2**53 - 1)</code> - 2414 <a href="https://tc39.github.io/ecma262/#sec-number.max_safe_integer"><code>Number.MAX_SAFE_INTEGER</code></a> <code>(2**53 - 1)</code> will lose precision.</p> 2415 <h5>napi_create_double<span><a class="mark" href="#n_api_napi_create_double" id="n_api_napi_create_double">#</a></span></h5> 2416 <div class="api_metadata"> 2417 <span>Added in: v8.4.0</span> 2418 <span>N-API version: 1</span> 2419 </div> 2420 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_double</span><span class="hljs-params">(napi_env env, <span class="hljs-type">double</span> value, napi_value* result)</span></code></pre> 2421 <ul> 2422 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2423 <li><code>[in] value</code>: Double-precision value to be represented in JavaScript.</li> 2424 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2425 </ul> 2426 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2427 <p>This API is used to convert from the C <code>double</code> type to the JavaScript 2428 <code>number</code> type.</p> 2429 <p>The JavaScript <code>number</code> type is described in 2430 <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type">Section 6.1.6</a> of the ECMAScript Language Specification.</p> 2431 <h5>napi_create_bigint_int64<span><a class="mark" href="#n_api_napi_create_bigint_int64" id="n_api_napi_create_bigint_int64">#</a></span></h5> 2432 <div class="api_metadata"> 2433 <span>Added in: v10.7.0</span> 2434 <span>N-API version: 6</span> 2435 </div> 2436 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_bigint_int64</span><span class="hljs-params">(napi_env env, 2437 <span class="hljs-type">int64_t</span> value, 2438 napi_value* result)</span>;</code></pre> 2439 <ul> 2440 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2441 <li><code>[in] value</code>: Integer value to be represented in JavaScript.</li> 2442 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>BigInt</code>.</li> 2443 </ul> 2444 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2445 <p>This API converts the C <code>int64_t</code> type to the JavaScript <code>BigInt</code> type.</p> 2446 <h5>napi_create_bigint_uint64<span><a class="mark" href="#n_api_napi_create_bigint_uint64" id="n_api_napi_create_bigint_uint64">#</a></span></h5> 2447 <div class="api_metadata"> 2448 <span>Added in: v10.7.0</span> 2449 <span>N-API version: 6</span> 2450 </div> 2451 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_bigint_uint64</span><span class="hljs-params">(napi_env env, 2452 <span class="hljs-type">uint64_t</span> value, 2453 napi_value* result)</span>;</code></pre> 2454 <ul> 2455 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2456 <li><code>[in] value</code>: Unsigned integer value to be represented in JavaScript.</li> 2457 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>BigInt</code>.</li> 2458 </ul> 2459 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2460 <p>This API converts the C <code>uint64_t</code> type to the JavaScript <code>BigInt</code> type.</p> 2461 <h5>napi_create_bigint_words<span><a class="mark" href="#n_api_napi_create_bigint_words" id="n_api_napi_create_bigint_words">#</a></span></h5> 2462 <div class="api_metadata"> 2463 <span>Added in: v10.7.0</span> 2464 <span>N-API version: 6</span> 2465 </div> 2466 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_bigint_words</span><span class="hljs-params">(napi_env env, 2467 <span class="hljs-type">int</span> sign_bit, 2468 <span class="hljs-type">size_t</span> word_count, 2469 <span class="hljs-keyword">const</span> <span class="hljs-type">uint64_t</span>* words, 2470 napi_value* result)</span>;</code></pre> 2471 <ul> 2472 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2473 <li><code>[in] sign_bit</code>: Determines if the resulting <code>BigInt</code> will be positive or 2474 negative.</li> 2475 <li><code>[in] word_count</code>: The length of the <code>words</code> array.</li> 2476 <li><code>[in] words</code>: An array of <code>uint64_t</code> little-endian 64-bit words.</li> 2477 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>BigInt</code>.</li> 2478 </ul> 2479 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2480 <p>This API converts an array of unsigned 64-bit words into a single <code>BigInt</code> 2481 value.</p> 2482 <p>The resulting <code>BigInt</code> is calculated as: (–1)<sup><code>sign_bit</code></sup> (<code>words[0]</code> 2483 × (2<sup>64</sup>)<sup>0</sup> + <code>words[1]</code> × (2<sup>64</sup>)<sup>1</sup> + …)</p> 2484 <h5>napi_create_string_latin1<span><a class="mark" href="#n_api_napi_create_string_latin1" id="n_api_napi_create_string_latin1">#</a></span></h5> 2485 <div class="api_metadata"> 2486 <span>Added in: v8.0.0</span> 2487 <span>N-API version: 1</span> 2488 </div> 2489 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_string_latin1</span><span class="hljs-params">(napi_env env, 2490 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* str, 2491 <span class="hljs-type">size_t</span> length, 2492 napi_value* result)</span>;</code></pre> 2493 <ul> 2494 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2495 <li><code>[in] str</code>: Character buffer representing an ISO-8859-1-encoded string.</li> 2496 <li><code>[in] length</code>: The length of the string in bytes, or <code>NAPI_AUTO_LENGTH</code> if it 2497 is null-terminated.</li> 2498 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>string</code>.</li> 2499 </ul> 2500 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2501 <p>This API creates a JavaScript <code>string</code> value from an ISO-8859-1-encoded C 2502 string. The native string is copied.</p> 2503 <p>The JavaScript <code>string</code> type is described in 2504 <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type">Section 6.1.4</a> of the ECMAScript Language Specification.</p> 2505 <h5>napi_create_string_utf16<span><a class="mark" href="#n_api_napi_create_string_utf16" id="n_api_napi_create_string_utf16">#</a></span></h5> 2506 <div class="api_metadata"> 2507 <span>Added in: v8.0.0</span> 2508 <span>N-API version: 1</span> 2509 </div> 2510 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_string_utf16</span><span class="hljs-params">(napi_env env, 2511 <span class="hljs-keyword">const</span> <span class="hljs-type">char16_t</span>* str, 2512 <span class="hljs-type">size_t</span> length, 2513 napi_value* result)</span></code></pre> 2514 <ul> 2515 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2516 <li><code>[in] str</code>: Character buffer representing a UTF16-LE-encoded string.</li> 2517 <li><code>[in] length</code>: The length of the string in two-byte code units, or 2518 <code>NAPI_AUTO_LENGTH</code> if it is null-terminated.</li> 2519 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>string</code>.</li> 2520 </ul> 2521 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2522 <p>This API creates a JavaScript <code>string</code> value from a UTF16-LE-encoded C string. 2523 The native string is copied.</p> 2524 <p>The JavaScript <code>string</code> type is described in 2525 <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type">Section 6.1.4</a> of the ECMAScript Language Specification.</p> 2526 <h5>napi_create_string_utf8<span><a class="mark" href="#n_api_napi_create_string_utf8" id="n_api_napi_create_string_utf8">#</a></span></h5> 2527 <div class="api_metadata"> 2528 <span>Added in: v8.0.0</span> 2529 <span>N-API version: 1</span> 2530 </div> 2531 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_string_utf8</span><span class="hljs-params">(napi_env env, 2532 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* str, 2533 <span class="hljs-type">size_t</span> length, 2534 napi_value* result)</span></code></pre> 2535 <ul> 2536 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2537 <li><code>[in] str</code>: Character buffer representing a UTF8-encoded string.</li> 2538 <li><code>[in] length</code>: The length of the string in bytes, or <code>NAPI_AUTO_LENGTH</code> if it 2539 is null-terminated.</li> 2540 <li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>string</code>.</li> 2541 </ul> 2542 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2543 <p>This API creates a JavaScript <code>string</code> value from a UTF8-encoded C string. 2544 The native string is copied.</p> 2545 <p>The JavaScript <code>string</code> type is described in 2546 <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type">Section 6.1.4</a> of the ECMAScript Language Specification.</p> 2547 <h4>Functions to convert from Node-API to C types<span><a class="mark" href="#n_api_functions_to_convert_from_node_api_to_c_types" id="n_api_functions_to_convert_from_node_api_to_c_types">#</a></span></h4> 2548 <h5>napi_get_array_length<span><a class="mark" href="#n_api_napi_get_array_length" id="n_api_napi_get_array_length">#</a></span></h5> 2549 <div class="api_metadata"> 2550 <span>Added in: v8.0.0</span> 2551 <span>N-API version: 1</span> 2552 </div> 2553 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_array_length</span><span class="hljs-params">(napi_env env, 2554 napi_value value, 2555 <span class="hljs-type">uint32_t</span>* result)</span></code></pre> 2556 <ul> 2557 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2558 <li><code>[in] value</code>: <code>napi_value</code> representing the JavaScript <code>Array</code> whose length is 2559 being queried.</li> 2560 <li><code>[out] result</code>: <code>uint32</code> representing length of the array.</li> 2561 </ul> 2562 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2563 <p>This API returns the length of an array.</p> 2564 <p><code>Array</code> length is described in <a href="https://tc39.github.io/ecma262/#sec-properties-of-array-instances-length">Section 22.1.4.1</a> of the ECMAScript Language 2565 Specification.</p> 2566 <h5>napi_get_arraybuffer_info<span><a class="mark" href="#n_api_napi_get_arraybuffer_info" id="n_api_napi_get_arraybuffer_info">#</a></span></h5> 2567 <div class="api_metadata"> 2568 <span>Added in: v8.0.0</span> 2569 <span>N-API version: 1</span> 2570 </div> 2571 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_arraybuffer_info</span><span class="hljs-params">(napi_env env, 2572 napi_value arraybuffer, 2573 <span class="hljs-type">void</span>** data, 2574 <span class="hljs-type">size_t</span>* byte_length)</span></code></pre> 2575 <ul> 2576 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2577 <li><code>[in] arraybuffer</code>: <code>napi_value</code> representing the <code>ArrayBuffer</code> being queried.</li> 2578 <li><code>[out] data</code>: The underlying data buffer of the <code>ArrayBuffer</code>. If byte_length 2579 is <code>0</code>, this may be <code>NULL</code> or any other pointer value.</li> 2580 <li><code>[out] byte_length</code>: Length in bytes of the underlying data buffer.</li> 2581 </ul> 2582 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2583 <p>This API is used to retrieve the underlying data buffer of an <code>ArrayBuffer</code> and 2584 its length.</p> 2585 <p><em>WARNING</em>: Use caution while using this API. The lifetime of the underlying data 2586 buffer is managed by the <code>ArrayBuffer</code> even after it's returned. A 2587 possible safe way to use this API is in conjunction with 2588 <a href="#n_api_napi_create_reference"><code>napi_create_reference</code></a>, which can be used to guarantee control over the 2589 lifetime of the <code>ArrayBuffer</code>. It's also safe to use the returned data buffer 2590 within the same callback as long as there are no calls to other APIs that might 2591 trigger a GC.</p> 2592 <h5>napi_get_buffer_info<span><a class="mark" href="#n_api_napi_get_buffer_info" id="n_api_napi_get_buffer_info">#</a></span></h5> 2593 <div class="api_metadata"> 2594 <span>Added in: v8.0.0</span> 2595 <span>N-API version: 1</span> 2596 </div> 2597 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_buffer_info</span><span class="hljs-params">(napi_env env, 2598 napi_value value, 2599 <span class="hljs-type">void</span>** data, 2600 <span class="hljs-type">size_t</span>* length)</span></code></pre> 2601 <ul> 2602 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2603 <li><code>[in] value</code>: <code>napi_value</code> representing the <code>node::Buffer</code> being queried.</li> 2604 <li><code>[out] data</code>: The underlying data buffer of the <code>node::Buffer</code>. 2605 If length is <code>0</code>, this may be <code>NULL</code> or any other pointer value.</li> 2606 <li><code>[out] length</code>: Length in bytes of the underlying data buffer.</li> 2607 </ul> 2608 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2609 <p>This API is used to retrieve the underlying data buffer of a <code>node::Buffer</code> 2610 and it's length.</p> 2611 <p><em>Warning</em>: Use caution while using this API since the underlying data buffer's 2612 lifetime is not guaranteed if it's managed by the VM.</p> 2613 <h5>napi_get_prototype<span><a class="mark" href="#n_api_napi_get_prototype" id="n_api_napi_get_prototype">#</a></span></h5> 2614 <div class="api_metadata"> 2615 <span>Added in: v8.0.0</span> 2616 <span>N-API version: 1</span> 2617 </div> 2618 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_prototype</span><span class="hljs-params">(napi_env env, 2619 napi_value object, 2620 napi_value* result)</span></code></pre> 2621 <ul> 2622 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2623 <li><code>[in] object</code>: <code>napi_value</code> representing JavaScript <code>Object</code> whose prototype 2624 to return. This returns the equivalent of <code>Object.getPrototypeOf</code> (which is 2625 not the same as the function's <code>prototype</code> property).</li> 2626 <li><code>[out] result</code>: <code>napi_value</code> representing prototype of the given object.</li> 2627 </ul> 2628 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2629 <h5>napi_get_typedarray_info<span><a class="mark" href="#n_api_napi_get_typedarray_info" id="n_api_napi_get_typedarray_info">#</a></span></h5> 2630 <div class="api_metadata"> 2631 <span>Added in: v8.0.0</span> 2632 <span>N-API version: 1</span> 2633 </div> 2634 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_typedarray_info</span><span class="hljs-params">(napi_env env, 2635 napi_value typedarray, 2636 napi_typedarray_type* type, 2637 <span class="hljs-type">size_t</span>* length, 2638 <span class="hljs-type">void</span>** data, 2639 napi_value* arraybuffer, 2640 <span class="hljs-type">size_t</span>* byte_offset)</span></code></pre> 2641 <ul> 2642 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2643 <li><code>[in] typedarray</code>: <code>napi_value</code> representing the <code>TypedArray</code> whose 2644 properties to query.</li> 2645 <li><code>[out] type</code>: Scalar datatype of the elements within the <code>TypedArray</code>.</li> 2646 <li><code>[out] length</code>: The number of elements in the <code>TypedArray</code>.</li> 2647 <li><code>[out] data</code>: The data buffer underlying the <code>TypedArray</code> adjusted by 2648 the <code>byte_offset</code> value so that it points to the first element in the 2649 <code>TypedArray</code>. If the length of the array is <code>0</code>, this may be <code>NULL</code> or 2650 any other pointer value.</li> 2651 <li><code>[out] arraybuffer</code>: The <code>ArrayBuffer</code> underlying the <code>TypedArray</code>.</li> 2652 <li><code>[out] byte_offset</code>: The byte offset within the underlying native array 2653 at which the first element of the arrays is located. The value for the data 2654 parameter has already been adjusted so that data points to the first element 2655 in the array. Therefore, the first byte of the native array would be at 2656 <code>data - byte_offset</code>.</li> 2657 </ul> 2658 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2659 <p>This API returns various properties of a typed array.</p> 2660 <p><em>Warning</em>: Use caution while using this API since the underlying data buffer 2661 is managed by the VM.</p> 2662 <h5>napi_get_dataview_info<span><a class="mark" href="#n_api_napi_get_dataview_info" id="n_api_napi_get_dataview_info">#</a></span></h5> 2663 <div class="api_metadata"> 2664 <span>Added in: v8.3.0</span> 2665 <span>N-API version: 1</span> 2666 </div> 2667 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_dataview_info</span><span class="hljs-params">(napi_env env, 2668 napi_value dataview, 2669 <span class="hljs-type">size_t</span>* byte_length, 2670 <span class="hljs-type">void</span>** data, 2671 napi_value* arraybuffer, 2672 <span class="hljs-type">size_t</span>* byte_offset)</span></code></pre> 2673 <ul> 2674 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2675 <li><code>[in] dataview</code>: <code>napi_value</code> representing the <code>DataView</code> whose 2676 properties to query.</li> 2677 <li><code>[out] byte_length</code>: Number of bytes in the <code>DataView</code>.</li> 2678 <li><code>[out] data</code>: The data buffer underlying the <code>DataView</code>. 2679 If byte_length is <code>0</code>, this may be <code>NULL</code> or any other pointer value.</li> 2680 <li><code>[out] arraybuffer</code>: <code>ArrayBuffer</code> underlying the <code>DataView</code>.</li> 2681 <li><code>[out] byte_offset</code>: The byte offset within the data buffer from which 2682 to start projecting the <code>DataView</code>.</li> 2683 </ul> 2684 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2685 <p>This API returns various properties of a <code>DataView</code>.</p> 2686 <h5>napi_get_date_value<span><a class="mark" href="#n_api_napi_get_date_value" id="n_api_napi_get_date_value">#</a></span></h5> 2687 <div class="api_metadata"> 2688 <span>Added in: v11.11.0, v10.17.0</span> 2689 <span>N-API version: 5</span> 2690 </div> 2691 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_date_value</span><span class="hljs-params">(napi_env env, 2692 napi_value value, 2693 <span class="hljs-type">double</span>* result)</span></code></pre> 2694 <ul> 2695 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2696 <li><code>[in] value</code>: <code>napi_value</code> representing a JavaScript <code>Date</code>.</li> 2697 <li><code>[out] result</code>: Time value as a <code>double</code> represented as milliseconds since 2698 midnight at the beginning of 01 January, 1970 UTC.</li> 2699 </ul> 2700 <p>This API does not observe leap seconds; they are ignored, as 2701 ECMAScript aligns with POSIX time specification.</p> 2702 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-date <code>napi_value</code> is passed 2703 in it returns <code>napi_date_expected</code>.</p> 2704 <p>This API returns the C double primitive of time value for the given JavaScript 2705 <code>Date</code>.</p> 2706 <h5>napi_get_value_bool<span><a class="mark" href="#n_api_napi_get_value_bool" id="n_api_napi_get_value_bool">#</a></span></h5> 2707 <div class="api_metadata"> 2708 <span>Added in: v8.0.0</span> 2709 <span>N-API version: 1</span> 2710 </div> 2711 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_bool</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 2712 <ul> 2713 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2714 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>Boolean</code>.</li> 2715 <li><code>[out] result</code>: C boolean primitive equivalent of the given JavaScript 2716 <code>Boolean</code>.</li> 2717 </ul> 2718 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-boolean <code>napi_value</code> is 2719 passed in it returns <code>napi_boolean_expected</code>.</p> 2720 <p>This API returns the C boolean primitive equivalent of the given JavaScript 2721 <code>Boolean</code>.</p> 2722 <h5>napi_get_value_double<span><a class="mark" href="#n_api_napi_get_value_double" id="n_api_napi_get_value_double">#</a></span></h5> 2723 <div class="api_metadata"> 2724 <span>Added in: v8.0.0</span> 2725 <span>N-API version: 1</span> 2726 </div> 2727 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_double</span><span class="hljs-params">(napi_env env, 2728 napi_value value, 2729 <span class="hljs-type">double</span>* result)</span></code></pre> 2730 <ul> 2731 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2732 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2733 <li><code>[out] result</code>: C double primitive equivalent of the given JavaScript 2734 <code>number</code>.</li> 2735 </ul> 2736 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> is passed 2737 in it returns <code>napi_number_expected</code>.</p> 2738 <p>This API returns the C double primitive equivalent of the given JavaScript 2739 <code>number</code>.</p> 2740 <h5>napi_get_value_bigint_int64<span><a class="mark" href="#n_api_napi_get_value_bigint_int64" id="n_api_napi_get_value_bigint_int64">#</a></span></h5> 2741 <div class="api_metadata"> 2742 <span>Added in: v10.7.0</span> 2743 <span>N-API version: 6</span> 2744 </div> 2745 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_bigint_int64</span><span class="hljs-params">(napi_env env, 2746 napi_value value, 2747 <span class="hljs-type">int64_t</span>* result, 2748 <span class="hljs-type">bool</span>* lossless)</span>;</code></pre> 2749 <ul> 2750 <li><code>[in] env</code>: The environment that the API is invoked under</li> 2751 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>BigInt</code>.</li> 2752 <li><code>[out] result</code>: C <code>int64_t</code> primitive equivalent of the given JavaScript 2753 <code>BigInt</code>.</li> 2754 <li><code>[out] lossless</code>: Indicates whether the <code>BigInt</code> value was converted 2755 losslessly.</li> 2756 </ul> 2757 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>BigInt</code> is passed in it 2758 returns <code>napi_bigint_expected</code>.</p> 2759 <p>This API returns the C <code>int64_t</code> primitive equivalent of the given JavaScript 2760 <code>BigInt</code>. If needed it will truncate the value, setting <code>lossless</code> to <code>false</code>.</p> 2761 <h5>napi_get_value_bigint_uint64<span><a class="mark" href="#n_api_napi_get_value_bigint_uint64" id="n_api_napi_get_value_bigint_uint64">#</a></span></h5> 2762 <div class="api_metadata"> 2763 <span>Added in: v10.7.0</span> 2764 <span>N-API version: 6</span> 2765 </div> 2766 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_bigint_uint64</span><span class="hljs-params">(napi_env env, 2767 napi_value value, 2768 <span class="hljs-type">uint64_t</span>* result, 2769 <span class="hljs-type">bool</span>* lossless)</span>;</code></pre> 2770 <ul> 2771 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2772 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>BigInt</code>.</li> 2773 <li><code>[out] result</code>: C <code>uint64_t</code> primitive equivalent of the given JavaScript 2774 <code>BigInt</code>.</li> 2775 <li><code>[out] lossless</code>: Indicates whether the <code>BigInt</code> value was converted 2776 losslessly.</li> 2777 </ul> 2778 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>BigInt</code> is passed in it 2779 returns <code>napi_bigint_expected</code>.</p> 2780 <p>This API returns the C <code>uint64_t</code> primitive equivalent of the given JavaScript 2781 <code>BigInt</code>. If needed it will truncate the value, setting <code>lossless</code> to <code>false</code>.</p> 2782 <h5>napi_get_value_bigint_words<span><a class="mark" href="#n_api_napi_get_value_bigint_words" id="n_api_napi_get_value_bigint_words">#</a></span></h5> 2783 <div class="api_metadata"> 2784 <span>Added in: v10.7.0</span> 2785 <span>N-API version: 6</span> 2786 </div> 2787 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_bigint_words</span><span class="hljs-params">(napi_env env, 2788 napi_value value, 2789 <span class="hljs-type">int</span>* sign_bit, 2790 <span class="hljs-type">size_t</span>* word_count, 2791 <span class="hljs-type">uint64_t</span>* words)</span>;</code></pre> 2792 <ul> 2793 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2794 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>BigInt</code>.</li> 2795 <li><code>[out] sign_bit</code>: Integer representing if the JavaScript <code>BigInt</code> is positive 2796 or negative.</li> 2797 <li><code>[in/out] word_count</code>: Must be initialized to the length of the <code>words</code> 2798 array. Upon return, it will be set to the actual number of words that 2799 would be needed to store this <code>BigInt</code>.</li> 2800 <li><code>[out] words</code>: Pointer to a pre-allocated 64-bit word array.</li> 2801 </ul> 2802 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2803 <p>This API converts a single <code>BigInt</code> value into a sign bit, 64-bit little-endian 2804 array, and the number of elements in the array. <code>sign_bit</code> and <code>words</code> may be 2805 both set to <code>NULL</code>, in order to get only <code>word_count</code>.</p> 2806 <h5>napi_get_value_external<span><a class="mark" href="#n_api_napi_get_value_external" id="n_api_napi_get_value_external">#</a></span></h5> 2807 <div class="api_metadata"> 2808 <span>Added in: v8.0.0</span> 2809 <span>N-API version: 1</span> 2810 </div> 2811 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_external</span><span class="hljs-params">(napi_env env, 2812 napi_value value, 2813 <span class="hljs-type">void</span>** result)</span></code></pre> 2814 <ul> 2815 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2816 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript external value.</li> 2817 <li><code>[out] result</code>: Pointer to the data wrapped by the JavaScript external value.</li> 2818 </ul> 2819 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-external <code>napi_value</code> is 2820 passed in it returns <code>napi_invalid_arg</code>.</p> 2821 <p>This API retrieves the external data pointer that was previously passed to 2822 <code>napi_create_external()</code>.</p> 2823 <h5>napi_get_value_int32<span><a class="mark" href="#n_api_napi_get_value_int32" id="n_api_napi_get_value_int32">#</a></span></h5> 2824 <div class="api_metadata"> 2825 <span>Added in: v8.0.0</span> 2826 <span>N-API version: 1</span> 2827 </div> 2828 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_int32</span><span class="hljs-params">(napi_env env, 2829 napi_value value, 2830 <span class="hljs-type">int32_t</span>* result)</span></code></pre> 2831 <ul> 2832 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2833 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2834 <li><code>[out] result</code>: C <code>int32</code> primitive equivalent of the given JavaScript 2835 <code>number</code>.</li> 2836 </ul> 2837 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> 2838 is passed in <code>napi_number_expected</code>.</p> 2839 <p>This API returns the C <code>int32</code> primitive equivalent 2840 of the given JavaScript <code>number</code>.</p> 2841 <p>If the number exceeds the range of the 32 bit integer, then the result is 2842 truncated to the equivalent of the bottom 32 bits. This can result in a large 2843 positive number becoming a negative number if the value is > 2<sup>31</sup> - 1.</p> 2844 <p>Non-finite number values (<code>NaN</code>, <code>+Infinity</code>, or <code>-Infinity</code>) set the 2845 result to zero.</p> 2846 <h5>napi_get_value_int64<span><a class="mark" href="#n_api_napi_get_value_int64" id="n_api_napi_get_value_int64">#</a></span></h5> 2847 <div class="api_metadata"> 2848 <span>Added in: v8.0.0</span> 2849 <span>N-API version: 1</span> 2850 </div> 2851 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_int64</span><span class="hljs-params">(napi_env env, 2852 napi_value value, 2853 <span class="hljs-type">int64_t</span>* result)</span></code></pre> 2854 <ul> 2855 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2856 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2857 <li><code>[out] result</code>: C <code>int64</code> primitive equivalent of the given JavaScript 2858 <code>number</code>.</li> 2859 </ul> 2860 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> 2861 is passed in it returns <code>napi_number_expected</code>.</p> 2862 <p>This API returns the C <code>int64</code> primitive equivalent of the given JavaScript 2863 <code>number</code>.</p> 2864 <p><code>number</code> values outside the range of <a href="https://tc39.github.io/ecma262/#sec-number.min_safe_integer"><code>Number.MIN_SAFE_INTEGER</code></a> 2865 <code>-(2**53 - 1)</code> - <a href="https://tc39.github.io/ecma262/#sec-number.max_safe_integer"><code>Number.MAX_SAFE_INTEGER</code></a> <code>(2**53 - 1)</code> will lose 2866 precision.</p> 2867 <p>Non-finite number values (<code>NaN</code>, <code>+Infinity</code>, or <code>-Infinity</code>) set the 2868 result to zero.</p> 2869 <h5>napi_get_value_string_latin1<span><a class="mark" href="#n_api_napi_get_value_string_latin1" id="n_api_napi_get_value_string_latin1">#</a></span></h5> 2870 <div class="api_metadata"> 2871 <span>Added in: v8.0.0</span> 2872 <span>N-API version: 1</span> 2873 </div> 2874 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_string_latin1</span><span class="hljs-params">(napi_env env, 2875 napi_value value, 2876 <span class="hljs-type">char</span>* buf, 2877 <span class="hljs-type">size_t</span> bufsize, 2878 <span class="hljs-type">size_t</span>* result)</span></code></pre> 2879 <ul> 2880 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2881 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript string.</li> 2882 <li><code>[in] buf</code>: Buffer to write the ISO-8859-1-encoded string into. If <code>NULL</code> is 2883 passed in, the length of the string in bytes and excluding the null terminator 2884 is returned in <code>result</code>.</li> 2885 <li><code>[in] bufsize</code>: Size of the destination buffer. When this value is 2886 insufficient, the returned string is truncated and null-terminated.</li> 2887 <li><code>[out] result</code>: Number of bytes copied into the buffer, excluding the null 2888 terminator.</li> 2889 </ul> 2890 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>string</code> <code>napi_value</code> 2891 is passed in it returns <code>napi_string_expected</code>.</p> 2892 <p>This API returns the ISO-8859-1-encoded string corresponding the value passed 2893 in.</p> 2894 <h5>napi_get_value_string_utf8<span><a class="mark" href="#n_api_napi_get_value_string_utf8" id="n_api_napi_get_value_string_utf8">#</a></span></h5> 2895 <div class="api_metadata"> 2896 <span>Added in: v8.0.0</span> 2897 <span>N-API version: 1</span> 2898 </div> 2899 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_string_utf8</span><span class="hljs-params">(napi_env env, 2900 napi_value value, 2901 <span class="hljs-type">char</span>* buf, 2902 <span class="hljs-type">size_t</span> bufsize, 2903 <span class="hljs-type">size_t</span>* result)</span></code></pre> 2904 <ul> 2905 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2906 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript string.</li> 2907 <li><code>[in] buf</code>: Buffer to write the UTF8-encoded string into. If <code>NULL</code> is passed 2908 in, the length of the string in bytes and excluding the null terminator is 2909 returned in <code>result</code>.</li> 2910 <li><code>[in] bufsize</code>: Size of the destination buffer. When this value is 2911 insufficient, the returned string is truncated and null-terminated.</li> 2912 <li><code>[out] result</code>: Number of bytes copied into the buffer, excluding the null 2913 terminator.</li> 2914 </ul> 2915 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>string</code> <code>napi_value</code> 2916 is passed in it returns <code>napi_string_expected</code>.</p> 2917 <p>This API returns the UTF8-encoded string corresponding the value passed in.</p> 2918 <h5>napi_get_value_string_utf16<span><a class="mark" href="#n_api_napi_get_value_string_utf16" id="n_api_napi_get_value_string_utf16">#</a></span></h5> 2919 <div class="api_metadata"> 2920 <span>Added in: v8.0.0</span> 2921 <span>N-API version: 1</span> 2922 </div> 2923 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_string_utf16</span><span class="hljs-params">(napi_env env, 2924 napi_value value, 2925 <span class="hljs-type">char16_t</span>* buf, 2926 <span class="hljs-type">size_t</span> bufsize, 2927 <span class="hljs-type">size_t</span>* result)</span></code></pre> 2928 <ul> 2929 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2930 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript string.</li> 2931 <li><code>[in] buf</code>: Buffer to write the UTF16-LE-encoded string into. If <code>NULL</code> is 2932 passed in, the length of the string in 2-byte code units and excluding the 2933 null terminator is returned.</li> 2934 <li><code>[in] bufsize</code>: Size of the destination buffer. When this value is 2935 insufficient, the returned string is truncated and null-terminated.</li> 2936 <li><code>[out] result</code>: Number of 2-byte code units copied into the buffer, excluding 2937 the null terminator.</li> 2938 </ul> 2939 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>string</code> <code>napi_value</code> 2940 is passed in it returns <code>napi_string_expected</code>.</p> 2941 <p>This API returns the UTF16-encoded string corresponding the value passed in.</p> 2942 <h5>napi_get_value_uint32<span><a class="mark" href="#n_api_napi_get_value_uint32" id="n_api_napi_get_value_uint32">#</a></span></h5> 2943 <div class="api_metadata"> 2944 <span>Added in: v8.0.0</span> 2945 <span>N-API version: 1</span> 2946 </div> 2947 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_uint32</span><span class="hljs-params">(napi_env env, 2948 napi_value value, 2949 <span class="hljs-type">uint32_t</span>* result)</span></code></pre> 2950 <ul> 2951 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2952 <li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2953 <li><code>[out] result</code>: C primitive equivalent of the given <code>napi_value</code> as a 2954 <code>uint32_t</code>.</li> 2955 </ul> 2956 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> 2957 is passed in it returns <code>napi_number_expected</code>.</p> 2958 <p>This API returns the C primitive equivalent of the given <code>napi_value</code> as a 2959 <code>uint32_t</code>.</p> 2960 <h4>Functions to get global instances<span><a class="mark" href="#n_api_functions_to_get_global_instances" id="n_api_functions_to_get_global_instances">#</a></span></h4> 2961 <h5>napi_get_boolean<span><a class="mark" href="#n_api_napi_get_boolean" id="n_api_napi_get_boolean">#</a></span></h5> 2962 <div class="api_metadata"> 2963 <span>Added in: v8.0.0</span> 2964 <span>N-API version: 1</span> 2965 </div> 2966 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_boolean</span><span class="hljs-params">(napi_env env, <span class="hljs-type">bool</span> value, napi_value* result)</span></code></pre> 2967 <ul> 2968 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2969 <li><code>[in] value</code>: The value of the boolean to retrieve.</li> 2970 <li><code>[out] result</code>: <code>napi_value</code> representing JavaScript <code>Boolean</code> singleton to 2971 retrieve.</li> 2972 </ul> 2973 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2974 <p>This API is used to return the JavaScript singleton object that is used to 2975 represent the given boolean value.</p> 2976 <h5>napi_get_global<span><a class="mark" href="#n_api_napi_get_global" id="n_api_napi_get_global">#</a></span></h5> 2977 <div class="api_metadata"> 2978 <span>Added in: v8.0.0</span> 2979 <span>N-API version: 1</span> 2980 </div> 2981 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_global</span><span class="hljs-params">(napi_env env, napi_value* result)</span></code></pre> 2982 <ul> 2983 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2984 <li><code>[out] result</code>: <code>napi_value</code> representing JavaScript <code>global</code> object.</li> 2985 </ul> 2986 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2987 <p>This API returns the <code>global</code> object.</p> 2988 <h5>napi_get_null<span><a class="mark" href="#n_api_napi_get_null" id="n_api_napi_get_null">#</a></span></h5> 2989 <div class="api_metadata"> 2990 <span>Added in: v8.0.0</span> 2991 <span>N-API version: 1</span> 2992 </div> 2993 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_null</span><span class="hljs-params">(napi_env env, napi_value* result)</span></code></pre> 2994 <ul> 2995 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 2996 <li><code>[out] result</code>: <code>napi_value</code> representing JavaScript <code>null</code> object.</li> 2997 </ul> 2998 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 2999 <p>This API returns the <code>null</code> object.</p> 3000 <h5>napi_get_undefined<span><a class="mark" href="#n_api_napi_get_undefined" id="n_api_napi_get_undefined">#</a></span></h5> 3001 <div class="api_metadata"> 3002 <span>Added in: v8.0.0</span> 3003 <span>N-API version: 1</span> 3004 </div> 3005 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_undefined</span><span class="hljs-params">(napi_env env, napi_value* result)</span></code></pre> 3006 <ul> 3007 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3008 <li><code>[out] result</code>: <code>napi_value</code> representing JavaScript Undefined value.</li> 3009 </ul> 3010 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3011 <p>This API returns the Undefined object.</p> 3012 </section><section><h3>Working with JavaScript values and abstract operations<span><a class="mark" href="#n_api_working_with_javascript_values_and_abstract_operations" id="n_api_working_with_javascript_values_and_abstract_operations">#</a></span></h3> 3013 <p>Node-API exposes a set of APIs to perform some abstract operations on JavaScript 3014 values. Some of these operations are documented under <a href="https://tc39.github.io/ecma262/#sec-abstract-operations">Section 7</a> 3015 of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</p> 3016 <p>These APIs support doing one of the following:</p> 3017 <ol> 3018 <li>Coerce JavaScript values to specific JavaScript types (such as <code>number</code> or 3019 <code>string</code>).</li> 3020 <li>Check the type of a JavaScript value.</li> 3021 <li>Check for equality between two JavaScript values.</li> 3022 </ol> 3023 <h4>napi_coerce_to_bool<span><a class="mark" href="#n_api_napi_coerce_to_bool" id="n_api_napi_coerce_to_bool">#</a></span></h4> 3024 <div class="api_metadata"> 3025 <span>Added in: v8.0.0</span> 3026 <span>N-API version: 1</span> 3027 </div> 3028 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_bool</span><span class="hljs-params">(napi_env env, 3029 napi_value value, 3030 napi_value* result)</span></code></pre> 3031 <ul> 3032 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3033 <li><code>[in] value</code>: The JavaScript value to coerce.</li> 3034 <li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>Boolean</code>.</li> 3035 </ul> 3036 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3037 <p>This API implements the abstract operation <code>ToBoolean()</code> as defined in 3038 <a href="https://tc39.github.io/ecma262/#sec-toboolean">Section 7.1.2</a> of the ECMAScript Language Specification. 3039 This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3040 <h4>napi_coerce_to_number<span><a class="mark" href="#n_api_napi_coerce_to_number" id="n_api_napi_coerce_to_number">#</a></span></h4> 3041 <div class="api_metadata"> 3042 <span>Added in: v8.0.0</span> 3043 <span>N-API version: 1</span> 3044 </div> 3045 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_number</span><span class="hljs-params">(napi_env env, 3046 napi_value value, 3047 napi_value* result)</span></code></pre> 3048 <ul> 3049 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3050 <li><code>[in] value</code>: The JavaScript value to coerce.</li> 3051 <li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>number</code>.</li> 3052 </ul> 3053 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3054 <p>This API implements the abstract operation <code>ToNumber()</code> as defined in 3055 <a href="https://tc39.github.io/ecma262/#sec-tonumber">Section 7.1.3</a> of the ECMAScript Language Specification. 3056 This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3057 <h4>napi_coerce_to_object<span><a class="mark" href="#n_api_napi_coerce_to_object" id="n_api_napi_coerce_to_object">#</a></span></h4> 3058 <div class="api_metadata"> 3059 <span>Added in: v8.0.0</span> 3060 <span>N-API version: 1</span> 3061 </div> 3062 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_object</span><span class="hljs-params">(napi_env env, 3063 napi_value value, 3064 napi_value* result)</span></code></pre> 3065 <ul> 3066 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3067 <li><code>[in] value</code>: The JavaScript value to coerce.</li> 3068 <li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>Object</code>.</li> 3069 </ul> 3070 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3071 <p>This API implements the abstract operation <code>ToObject()</code> as defined in 3072 <a href="https://tc39.github.io/ecma262/#sec-toobject">Section 7.1.13</a> of the ECMAScript Language Specification. 3073 This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3074 <h4>napi_coerce_to_string<span><a class="mark" href="#n_api_napi_coerce_to_string" id="n_api_napi_coerce_to_string">#</a></span></h4> 3075 <div class="api_metadata"> 3076 <span>Added in: v8.0.0</span> 3077 <span>N-API version: 1</span> 3078 </div> 3079 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_string</span><span class="hljs-params">(napi_env env, 3080 napi_value value, 3081 napi_value* result)</span></code></pre> 3082 <ul> 3083 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3084 <li><code>[in] value</code>: The JavaScript value to coerce.</li> 3085 <li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>string</code>.</li> 3086 </ul> 3087 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3088 <p>This API implements the abstract operation <code>ToString()</code> as defined in 3089 <a href="https://tc39.github.io/ecma262/#sec-toobject">Section 7.1.13</a> of the ECMAScript Language Specification. 3090 This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3091 <h4>napi_typeof<span><a class="mark" href="#n_api_napi_typeof" id="n_api_napi_typeof">#</a></span></h4> 3092 <div class="api_metadata"> 3093 <span>Added in: v8.0.0</span> 3094 <span>N-API version: 1</span> 3095 </div> 3096 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_typeof</span><span class="hljs-params">(napi_env env, napi_value value, napi_valuetype* result)</span></code></pre> 3097 <ul> 3098 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3099 <li><code>[in] value</code>: The JavaScript value whose type to query.</li> 3100 <li><code>[out] result</code>: The type of the JavaScript value.</li> 3101 </ul> 3102 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3103 <ul> 3104 <li><code>napi_invalid_arg</code> if the type of <code>value</code> is not a known ECMAScript type and 3105 <code>value</code> is not an External value.</li> 3106 </ul> 3107 <p>This API represents behavior similar to invoking the <code>typeof</code> Operator on 3108 the object as defined in <a href="https://tc39.github.io/ecma262/#sec-typeof-operator">Section 12.5.5</a> of the ECMAScript Language 3109 Specification. However, there are some differences:</p> 3110 <ol> 3111 <li>It has support for detecting an External value.</li> 3112 <li>It detects <code>null</code> as a separate type, while ECMAScript <code>typeof</code> would detect 3113 <code>object</code>.</li> 3114 </ol> 3115 <p>If <code>value</code> has a type that is invalid, an error is returned.</p> 3116 <h4>napi_instanceof<span><a class="mark" href="#n_api_napi_instanceof" id="n_api_napi_instanceof">#</a></span></h4> 3117 <div class="api_metadata"> 3118 <span>Added in: v8.0.0</span> 3119 <span>N-API version: 1</span> 3120 </div> 3121 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_instanceof</span><span class="hljs-params">(napi_env env, 3122 napi_value object, 3123 napi_value constructor, 3124 <span class="hljs-type">bool</span>* result)</span></code></pre> 3125 <ul> 3126 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3127 <li><code>[in] object</code>: The JavaScript value to check.</li> 3128 <li><code>[in] constructor</code>: The JavaScript function object of the constructor function 3129 to check against.</li> 3130 <li><code>[out] result</code>: Boolean that is set to true if <code>object instanceof constructor</code> 3131 is true.</li> 3132 </ul> 3133 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3134 <p>This API represents invoking the <code>instanceof</code> Operator on the object as 3135 defined in <a href="https://tc39.github.io/ecma262/#sec-instanceofoperator">Section 12.10.4</a> of the ECMAScript Language Specification.</p> 3136 <h4>napi_is_array<span><a class="mark" href="#n_api_napi_is_array" id="n_api_napi_is_array">#</a></span></h4> 3137 <div class="api_metadata"> 3138 <span>Added in: v8.0.0</span> 3139 <span>N-API version: 1</span> 3140 </div> 3141 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_array</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 3142 <ul> 3143 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3144 <li><code>[in] value</code>: The JavaScript value to check.</li> 3145 <li><code>[out] result</code>: Whether the given object is an array.</li> 3146 </ul> 3147 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3148 <p>This API represents invoking the <code>IsArray</code> operation on the object 3149 as defined in <a href="https://tc39.github.io/ecma262/#sec-isarray">Section 7.2.2</a> of the ECMAScript Language Specification.</p> 3150 <h4>napi_is_arraybuffer<span><a class="mark" href="#n_api_napi_is_arraybuffer" id="n_api_napi_is_arraybuffer">#</a></span></h4> 3151 <div class="api_metadata"> 3152 <span>Added in: v8.0.0</span> 3153 <span>N-API version: 1</span> 3154 </div> 3155 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_arraybuffer</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 3156 <ul> 3157 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3158 <li><code>[in] value</code>: The JavaScript value to check.</li> 3159 <li><code>[out] result</code>: Whether the given object is an <code>ArrayBuffer</code>.</li> 3160 </ul> 3161 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3162 <p>This API checks if the <code>Object</code> passed in is an array buffer.</p> 3163 <h4>napi_is_buffer<span><a class="mark" href="#n_api_napi_is_buffer" id="n_api_napi_is_buffer">#</a></span></h4> 3164 <div class="api_metadata"> 3165 <span>Added in: v8.0.0</span> 3166 <span>N-API version: 1</span> 3167 </div> 3168 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_buffer</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 3169 <ul> 3170 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3171 <li><code>[in] value</code>: The JavaScript value to check.</li> 3172 <li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a <code>node::Buffer</code> 3173 object.</li> 3174 </ul> 3175 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3176 <p>This API checks if the <code>Object</code> passed in is a buffer.</p> 3177 <h4>napi_is_date<span><a class="mark" href="#n_api_napi_is_date" id="n_api_napi_is_date">#</a></span></h4> 3178 <div class="api_metadata"> 3179 <span>Added in: v11.11.0, v10.17.0</span> 3180 <span>N-API version: 5</span> 3181 </div> 3182 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_date</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 3183 <ul> 3184 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3185 <li><code>[in] value</code>: The JavaScript value to check.</li> 3186 <li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a JavaScript <code>Date</code> 3187 object.</li> 3188 </ul> 3189 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3190 <p>This API checks if the <code>Object</code> passed in is a date.</p> 3191 <h4>napi_is_error<span><a class="mark" href="#n_api_napi_is_error_1" id="n_api_napi_is_error_1">#</a></span></h4> 3192 <div class="api_metadata"> 3193 <span>Added in: v8.0.0</span> 3194 <span>N-API version: 1</span> 3195 </div> 3196 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_error</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 3197 <ul> 3198 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3199 <li><code>[in] value</code>: The JavaScript value to check.</li> 3200 <li><code>[out] result</code>: Whether the given <code>napi_value</code> represents an <code>Error</code> object.</li> 3201 </ul> 3202 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3203 <p>This API checks if the <code>Object</code> passed in is an <code>Error</code>.</p> 3204 <h4>napi_is_typedarray<span><a class="mark" href="#n_api_napi_is_typedarray" id="n_api_napi_is_typedarray">#</a></span></h4> 3205 <div class="api_metadata"> 3206 <span>Added in: v8.0.0</span> 3207 <span>N-API version: 1</span> 3208 </div> 3209 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_typedarray</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 3210 <ul> 3211 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3212 <li><code>[in] value</code>: The JavaScript value to check.</li> 3213 <li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a <code>TypedArray</code>.</li> 3214 </ul> 3215 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3216 <p>This API checks if the <code>Object</code> passed in is a typed array.</p> 3217 <h4>napi_is_dataview<span><a class="mark" href="#n_api_napi_is_dataview" id="n_api_napi_is_dataview">#</a></span></h4> 3218 <div class="api_metadata"> 3219 <span>Added in: v8.3.0</span> 3220 <span>N-API version: 1</span> 3221 </div> 3222 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_dataview</span><span class="hljs-params">(napi_env env, napi_value value, <span class="hljs-type">bool</span>* result)</span></code></pre> 3223 <ul> 3224 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3225 <li><code>[in] value</code>: The JavaScript value to check.</li> 3226 <li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a <code>DataView</code>.</li> 3227 </ul> 3228 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3229 <p>This API checks if the <code>Object</code> passed in is a <code>DataView</code>.</p> 3230 <h4>napi_strict_equals<span><a class="mark" href="#n_api_napi_strict_equals" id="n_api_napi_strict_equals">#</a></span></h4> 3231 <div class="api_metadata"> 3232 <span>Added in: v8.0.0</span> 3233 <span>N-API version: 1</span> 3234 </div> 3235 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_strict_equals</span><span class="hljs-params">(napi_env env, 3236 napi_value lhs, 3237 napi_value rhs, 3238 <span class="hljs-type">bool</span>* result)</span></code></pre> 3239 <ul> 3240 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3241 <li><code>[in] lhs</code>: The JavaScript value to check.</li> 3242 <li><code>[in] rhs</code>: The JavaScript value to check against.</li> 3243 <li><code>[out] result</code>: Whether the two <code>napi_value</code> objects are equal.</li> 3244 </ul> 3245 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3246 <p>This API represents the invocation of the Strict Equality algorithm as 3247 defined in <a href="https://tc39.github.io/ecma262/#sec-strict-equality-comparison">Section 7.2.14</a> of the ECMAScript Language Specification.</p> 3248 <h4>napi_detach_arraybuffer<span><a class="mark" href="#n_api_napi_detach_arraybuffer" id="n_api_napi_detach_arraybuffer">#</a></span></h4> 3249 <div class="api_metadata"> 3250 <span>Added in: v13.0.0, v12.16.0, v10.22.0</span> 3251 <span>N-API version: 7</span> 3252 </div> 3253 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_detach_arraybuffer</span><span class="hljs-params">(napi_env env, 3254 napi_value arraybuffer)</span></code></pre> 3255 <ul> 3256 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3257 <li><code>[in] arraybuffer</code>: The JavaScript <code>ArrayBuffer</code> to be detached.</li> 3258 </ul> 3259 <p>Returns <code>napi_ok</code> if the API succeeded. If a non-detachable <code>ArrayBuffer</code> is 3260 passed in it returns <code>napi_detachable_arraybuffer_expected</code>.</p> 3261 <p>Generally, an <code>ArrayBuffer</code> is non-detachable if it has been detached before. 3262 The engine may impose additional conditions on whether an <code>ArrayBuffer</code> is 3263 detachable. For example, V8 requires that the <code>ArrayBuffer</code> be external, 3264 that is, created with <a href="#n_api_napi_create_external_arraybuffer"><code>napi_create_external_arraybuffer</code></a>.</p> 3265 <p>This API represents the invocation of the <code>ArrayBuffer</code> detach operation as 3266 defined in <a href="https://tc39.es/ecma262/#sec-detacharraybuffer">Section 24.1.1.3</a> of the ECMAScript Language Specification.</p> 3267 <h4>napi_is_detached_arraybuffer<span><a class="mark" href="#n_api_napi_is_detached_arraybuffer" id="n_api_napi_is_detached_arraybuffer">#</a></span></h4> 3268 <div class="api_metadata"> 3269 <span>Added in: v13.3.0, v12.16.0, v10.22.0</span> 3270 <span>N-API version: 7</span> 3271 </div> 3272 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_detached_arraybuffer</span><span class="hljs-params">(napi_env env, 3273 napi_value arraybuffer, 3274 <span class="hljs-type">bool</span>* result)</span></code></pre> 3275 <ul> 3276 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3277 <li><code>[in] arraybuffer</code>: The JavaScript <code>ArrayBuffer</code> to be checked.</li> 3278 <li><code>[out] result</code>: Whether the <code>arraybuffer</code> is detached.</li> 3279 </ul> 3280 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3281 <p>The <code>ArrayBuffer</code> is considered detached if its internal data is <code>null</code>.</p> 3282 <p>This API represents the invocation of the <code>ArrayBuffer</code> <code>IsDetachedBuffer</code> 3283 operation as defined in <a href="https://tc39.es/ecma262/#sec-isdetachedbuffer">Section 24.1.1.2</a> of the ECMAScript Language 3284 Specification.</p> 3285 </section><section><h3>Working with JavaScript properties<span><a class="mark" href="#n_api_working_with_javascript_properties" id="n_api_working_with_javascript_properties">#</a></span></h3> 3286 <p>Node-API exposes a set of APIs to get and set properties on JavaScript 3287 objects. Some of these types are documented under <a href="https://tc39.github.io/ecma262/#sec-abstract-operations">Section 7</a> of the 3288 <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</p> 3289 <p>Properties in JavaScript are represented as a tuple of a key and a value. 3290 Fundamentally, all property keys in Node-API can be represented in one of the 3291 following forms:</p> 3292 <ul> 3293 <li>Named: a simple UTF8-encoded string</li> 3294 <li>Integer-Indexed: an index value represented by <code>uint32_t</code></li> 3295 <li>JavaScript value: these are represented in Node-API by <code>napi_value</code>. This can 3296 be a <code>napi_value</code> representing a <code>string</code>, <code>number</code>, or <code>symbol</code>.</li> 3297 </ul> 3298 <p>Node-API values are represented by the type <code>napi_value</code>. 3299 Any Node-API call that requires a JavaScript value takes in a <code>napi_value</code>. 3300 However, it's the caller's responsibility to make sure that the 3301 <code>napi_value</code> in question is of the JavaScript type expected by the API.</p> 3302 <p>The APIs documented in this section provide a simple interface to 3303 get and set properties on arbitrary JavaScript objects represented by 3304 <code>napi_value</code>.</p> 3305 <p>For instance, consider the following JavaScript code snippet:</p> 3306 <pre><code class="language-js"><span class="hljs-keyword">const</span> obj = {}; 3307 obj.<span class="hljs-property">myProp</span> = <span class="hljs-number">123</span>;</code></pre> 3308 <p>The equivalent can be done using Node-API values with the following snippet:</p> 3309 <pre><code class="language-c">napi_status status = napi_generic_failure; 3310 3311 <span class="hljs-comment">// const obj = {}</span> 3312 napi_value obj, value; 3313 status = napi_create_object(env, &obj); 3314 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3315 3316 <span class="hljs-comment">// Create a napi_value for 123</span> 3317 status = napi_create_int32(env, <span class="hljs-number">123</span>, &value); 3318 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3319 3320 <span class="hljs-comment">// obj.myProp = 123</span> 3321 status = napi_set_named_property(env, obj, <span class="hljs-string">"myProp"</span>, value); 3322 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3323 <p>Indexed properties can be set in a similar manner. Consider the following 3324 JavaScript snippet:</p> 3325 <pre><code class="language-js"><span class="hljs-keyword">const</span> arr = []; 3326 arr[<span class="hljs-number">123</span>] = <span class="hljs-string">'hello'</span>;</code></pre> 3327 <p>The equivalent can be done using Node-API values with the following snippet:</p> 3328 <pre><code class="language-c">napi_status status = napi_generic_failure; 3329 3330 <span class="hljs-comment">// const arr = [];</span> 3331 napi_value arr, value; 3332 status = napi_create_array(env, &arr); 3333 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3334 3335 <span class="hljs-comment">// Create a napi_value for 'hello'</span> 3336 status = napi_create_string_utf8(env, <span class="hljs-string">"hello"</span>, NAPI_AUTO_LENGTH, &value); 3337 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3338 3339 <span class="hljs-comment">// arr[123] = 'hello';</span> 3340 status = napi_set_element(env, arr, <span class="hljs-number">123</span>, value); 3341 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3342 <p>Properties can be retrieved using the APIs described in this section. 3343 Consider the following JavaScript snippet:</p> 3344 <pre><code class="language-js"><span class="hljs-keyword">const</span> arr = []; 3345 <span class="hljs-keyword">const</span> value = arr[<span class="hljs-number">123</span>];</code></pre> 3346 <p>The following is the approximate equivalent of the Node-API counterpart:</p> 3347 <pre><code class="language-c">napi_status status = napi_generic_failure; 3348 3349 <span class="hljs-comment">// const arr = []</span> 3350 napi_value arr, value; 3351 status = napi_create_array(env, &arr); 3352 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3353 3354 <span class="hljs-comment">// const value = arr[123]</span> 3355 status = napi_get_element(env, arr, <span class="hljs-number">123</span>, &value); 3356 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3357 <p>Finally, multiple properties can also be defined on an object for performance 3358 reasons. Consider the following JavaScript:</p> 3359 <pre><code class="language-js"><span class="hljs-keyword">const</span> obj = {}; 3360 <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">defineProperties</span>(obj, { 3361 <span class="hljs-string">'foo'</span>: { <span class="hljs-attr">value</span>: <span class="hljs-number">123</span>, <span class="hljs-attr">writable</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">configurable</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">enumerable</span>: <span class="hljs-literal">true</span> }, 3362 <span class="hljs-string">'bar'</span>: { <span class="hljs-attr">value</span>: <span class="hljs-number">456</span>, <span class="hljs-attr">writable</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">configurable</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">enumerable</span>: <span class="hljs-literal">true</span> } 3363 });</code></pre> 3364 <p>The following is the approximate equivalent of the Node-API counterpart:</p> 3365 <pre><code class="language-c">napi_status status = napi_status_generic_failure; 3366 3367 <span class="hljs-comment">// const obj = {};</span> 3368 napi_value obj; 3369 status = napi_create_object(env, &obj); 3370 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3371 3372 <span class="hljs-comment">// Create napi_values for 123 and 456</span> 3373 napi_value fooValue, barValue; 3374 status = napi_create_int32(env, <span class="hljs-number">123</span>, &fooValue); 3375 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3376 status = napi_create_int32(env, <span class="hljs-number">456</span>, &barValue); 3377 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3378 3379 <span class="hljs-comment">// Set the properties</span> 3380 napi_property_descriptor descriptors[] = { 3381 { <span class="hljs-string">"foo"</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, fooValue, napi_writable | napi_configurable, <span class="hljs-literal">NULL</span> }, 3382 { <span class="hljs-string">"bar"</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, barValue, napi_writable | napi_configurable, <span class="hljs-literal">NULL</span> } 3383 } 3384 status = napi_define_properties(env, 3385 obj, 3386 <span class="hljs-keyword">sizeof</span>(descriptors) / <span class="hljs-keyword">sizeof</span>(descriptors[<span class="hljs-number">0</span>]), 3387 descriptors); 3388 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3389 <h4>Structures<span><a class="mark" href="#n_api_structures" id="n_api_structures">#</a></span></h4> 3390 <h5>napi_property_attributes<span><a class="mark" href="#n_api_napi_property_attributes" id="n_api_napi_property_attributes">#</a></span></h5> 3391 <div class="api_metadata"> 3392 <details class="changelog"><summary>History</summary> 3393 <table> 3394 <tbody><tr><th>Version</th><th>Changes</th></tr> 3395 <tr><td>v14.12.0</td> 3396 <td><p>added <code>napi_default_method</code> and <code>napi_default_property</code>.</p></td></tr> 3397 </tbody></table> 3398 </details> 3399 </div> 3400 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 3401 napi_default = <span class="hljs-number">0</span>, 3402 napi_writable = <span class="hljs-number">1</span> << <span class="hljs-number">0</span>, 3403 napi_enumerable = <span class="hljs-number">1</span> << <span class="hljs-number">1</span>, 3404 napi_configurable = <span class="hljs-number">1</span> << <span class="hljs-number">2</span>, 3405 3406 <span class="hljs-comment">// Used with napi_define_class to distinguish static properties</span> 3407 <span class="hljs-comment">// from instance properties. Ignored by napi_define_properties.</span> 3408 napi_static = <span class="hljs-number">1</span> << <span class="hljs-number">10</span>, 3409 3410 <span class="hljs-comment">// Default for class methods.</span> 3411 napi_default_method = napi_writable | napi_configurable, 3412 3413 <span class="hljs-comment">// Default for object properties, like in JS obj[prop].</span> 3414 napi_default_jsproperty = napi_writable | 3415 napi_enumerable | 3416 napi_configurable, 3417 } napi_property_attributes;</code></pre> 3418 <p><code>napi_property_attributes</code> are flags used to control the behavior of properties 3419 set on a JavaScript object. Other than <code>napi_static</code> they correspond to the 3420 attributes listed in <a href="https://tc39.github.io/ecma262/#table-2">Section 6.1.7.1</a> 3421 of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>. 3422 They can be one or more of the following bitflags:</p> 3423 <ul> 3424 <li><code>napi_default</code>: No explicit attributes are set on the property. By default, a 3425 property is read only, not enumerable and not configurable.</li> 3426 <li><code>napi_writable</code>: The property is writable.</li> 3427 <li><code>napi_enumerable</code>: The property is enumerable.</li> 3428 <li><code>napi_configurable</code>: The property is configurable as defined in 3429 <a href="https://tc39.github.io/ecma262/#table-2">Section 6.1.7.1</a> of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</li> 3430 <li><code>napi_static</code>: The property will be defined as a static property on a class as 3431 opposed to an instance property, which is the default. This is used only by 3432 <a href="#n_api_napi_define_class"><code>napi_define_class</code></a>. It is ignored by <code>napi_define_properties</code>.</li> 3433 <li><code>napi_default_method</code>: Like a method in a JS class, the property is 3434 configurable and writeable, but not enumerable.</li> 3435 <li><code>napi_default_jsproperty</code>: Like a property set via assignment in JavaScript, 3436 the property is writable, enumerable, and configurable.</li> 3437 </ul> 3438 <h5>napi_property_descriptor<span><a class="mark" href="#n_api_napi_property_descriptor" id="n_api_napi_property_descriptor">#</a></span></h5> 3439 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 3440 <span class="hljs-comment">// One of utf8name or name should be NULL.</span> 3441 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8name; 3442 napi_value name; 3443 3444 napi_callback method; 3445 napi_callback getter; 3446 napi_callback setter; 3447 napi_value value; 3448 3449 napi_property_attributes attributes; 3450 <span class="hljs-type">void</span>* data; 3451 } napi_property_descriptor;</code></pre> 3452 <ul> 3453 <li><code>utf8name</code>: Optional string describing the key for the property, 3454 encoded as UTF8. One of <code>utf8name</code> or <code>name</code> must be provided for the 3455 property.</li> 3456 <li><code>name</code>: Optional <code>napi_value</code> that points to a JavaScript string or symbol 3457 to be used as the key for the property. One of <code>utf8name</code> or <code>name</code> must 3458 be provided for the property.</li> 3459 <li><code>value</code>: The value that's retrieved by a get access of the property if the 3460 property is a data property. If this is passed in, set <code>getter</code>, <code>setter</code>, 3461 <code>method</code> and <code>data</code> to <code>NULL</code> (since these members won't be used).</li> 3462 <li><code>getter</code>: A function to call when a get access of the property is performed. 3463 If this is passed in, set <code>value</code> and <code>method</code> to <code>NULL</code> (since these members 3464 won't be used). The given function is called implicitly by the runtime when 3465 the property is accessed from JavaScript code (or if a get on the property is 3466 performed using a Node-API call). <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3467 <li><code>setter</code>: A function to call when a set access of the property is performed. 3468 If this is passed in, set <code>value</code> and <code>method</code> to <code>NULL</code> (since these members 3469 won't be used). The given function is called implicitly by the runtime when 3470 the property is set from JavaScript code (or if a set on the property is 3471 performed using a Node-API call). <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3472 <li><code>method</code>: Set this to make the property descriptor object's <code>value</code> 3473 property to be a JavaScript function represented by <code>method</code>. If this is 3474 passed in, set <code>value</code>, <code>getter</code> and <code>setter</code> to <code>NULL</code> (since these members 3475 won't be used). <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3476 <li><code>attributes</code>: The attributes associated with the particular property. See 3477 <a href="#n_api_napi_property_attributes"><code>napi_property_attributes</code></a>.</li> 3478 <li><code>data</code>: The callback data passed into <code>method</code>, <code>getter</code> and <code>setter</code> if this 3479 function is invoked.</li> 3480 </ul> 3481 <h4>Functions<span><a class="mark" href="#n_api_functions" id="n_api_functions">#</a></span></h4> 3482 <h5>napi_get_property_names<span><a class="mark" href="#n_api_napi_get_property_names" id="n_api_napi_get_property_names">#</a></span></h5> 3483 <div class="api_metadata"> 3484 <span>Added in: v8.0.0</span> 3485 <span>N-API version: 1</span> 3486 </div> 3487 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_property_names</span><span class="hljs-params">(napi_env env, 3488 napi_value object, 3489 napi_value* result)</span>;</code></pre> 3490 <ul> 3491 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3492 <li><code>[in] object</code>: The object from which to retrieve the properties.</li> 3493 <li><code>[out] result</code>: A <code>napi_value</code> representing an array of JavaScript values 3494 that represent the property names of the object. The API can be used to 3495 iterate over <code>result</code> using <a href="#n_api_napi_get_array_length"><code>napi_get_array_length</code></a> 3496 and <a href="#n_api_napi_get_element"><code>napi_get_element</code></a>.</li> 3497 </ul> 3498 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3499 <p>This API returns the names of the enumerable properties of <code>object</code> as an array 3500 of strings. The properties of <code>object</code> whose key is a symbol will not be 3501 included.</p> 3502 <h5>napi_get_all_property_names<span><a class="mark" href="#n_api_napi_get_all_property_names" id="n_api_napi_get_all_property_names">#</a></span></h5> 3503 <div class="api_metadata"> 3504 <span>Added in: v13.7.0, v10.20.0</span> 3505 <span>N-API version: 6</span> 3506 </div> 3507 <pre><code class="language-c">napi_get_all_property_names(napi_env env, 3508 napi_value object, 3509 napi_key_collection_mode key_mode, 3510 napi_key_filter key_filter, 3511 napi_key_conversion key_conversion, 3512 napi_value* result);</code></pre> 3513 <ul> 3514 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3515 <li><code>[in] object</code>: The object from which to retrieve the properties.</li> 3516 <li><code>[in] key_mode</code>: Whether to retrieve prototype properties as well.</li> 3517 <li><code>[in] key_filter</code>: Which properties to retrieve 3518 (enumerable/readable/writable).</li> 3519 <li><code>[in] key_conversion</code>: Whether to convert numbered property keys to strings.</li> 3520 <li><code>[out] result</code>: A <code>napi_value</code> representing an array of JavaScript values 3521 that represent the property names of the object. <a href="#n_api_napi_get_array_length"><code>napi_get_array_length</code></a> 3522 and <a href="#n_api_napi_get_element"><code>napi_get_element</code></a> can be used to iterate over <code>result</code>.</li> 3523 </ul> 3524 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3525 <p>This API returns an array containing the names of the available properties 3526 of this object.</p> 3527 <h5>napi_set_property<span><a class="mark" href="#n_api_napi_set_property" id="n_api_napi_set_property">#</a></span></h5> 3528 <div class="api_metadata"> 3529 <span>Added in: v8.0.0</span> 3530 <span>N-API version: 1</span> 3531 </div> 3532 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_property</span><span class="hljs-params">(napi_env env, 3533 napi_value object, 3534 napi_value key, 3535 napi_value value)</span>;</code></pre> 3536 <ul> 3537 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3538 <li><code>[in] object</code>: The object on which to set the property.</li> 3539 <li><code>[in] key</code>: The name of the property to set.</li> 3540 <li><code>[in] value</code>: The property value.</li> 3541 </ul> 3542 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3543 <p>This API set a property on the <code>Object</code> passed in.</p> 3544 <h5>napi_get_property<span><a class="mark" href="#n_api_napi_get_property" id="n_api_napi_get_property">#</a></span></h5> 3545 <div class="api_metadata"> 3546 <span>Added in: v8.0.0</span> 3547 <span>N-API version: 1</span> 3548 </div> 3549 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_property</span><span class="hljs-params">(napi_env env, 3550 napi_value object, 3551 napi_value key, 3552 napi_value* result)</span>;</code></pre> 3553 <ul> 3554 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3555 <li><code>[in] object</code>: The object from which to retrieve the property.</li> 3556 <li><code>[in] key</code>: The name of the property to retrieve.</li> 3557 <li><code>[out] result</code>: The value of the property.</li> 3558 </ul> 3559 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3560 <p>This API gets the requested property from the <code>Object</code> passed in.</p> 3561 <h5>napi_has_property<span><a class="mark" href="#n_api_napi_has_property" id="n_api_napi_has_property">#</a></span></h5> 3562 <div class="api_metadata"> 3563 <span>Added in: v8.0.0</span> 3564 <span>N-API version: 1</span> 3565 </div> 3566 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_property</span><span class="hljs-params">(napi_env env, 3567 napi_value object, 3568 napi_value key, 3569 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3570 <ul> 3571 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3572 <li><code>[in] object</code>: The object to query.</li> 3573 <li><code>[in] key</code>: The name of the property whose existence to check.</li> 3574 <li><code>[out] result</code>: Whether the property exists on the object or not.</li> 3575 </ul> 3576 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3577 <p>This API checks if the <code>Object</code> passed in has the named property.</p> 3578 <h5>napi_delete_property<span><a class="mark" href="#n_api_napi_delete_property" id="n_api_napi_delete_property">#</a></span></h5> 3579 <div class="api_metadata"> 3580 <span>Added in: v8.2.0</span> 3581 <span>N-API version: 1</span> 3582 </div> 3583 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_delete_property</span><span class="hljs-params">(napi_env env, 3584 napi_value object, 3585 napi_value key, 3586 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3587 <ul> 3588 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3589 <li><code>[in] object</code>: The object to query.</li> 3590 <li><code>[in] key</code>: The name of the property to delete.</li> 3591 <li><code>[out] result</code>: Whether the property deletion succeeded or not. <code>result</code> can 3592 optionally be ignored by passing <code>NULL</code>.</li> 3593 </ul> 3594 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3595 <p>This API attempts to delete the <code>key</code> own property from <code>object</code>.</p> 3596 <h5>napi_has_own_property<span><a class="mark" href="#n_api_napi_has_own_property" id="n_api_napi_has_own_property">#</a></span></h5> 3597 <div class="api_metadata"> 3598 <span>Added in: v8.2.0</span> 3599 <span>N-API version: 1</span> 3600 </div> 3601 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_own_property</span><span class="hljs-params">(napi_env env, 3602 napi_value object, 3603 napi_value key, 3604 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3605 <ul> 3606 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3607 <li><code>[in] object</code>: The object to query.</li> 3608 <li><code>[in] key</code>: The name of the own property whose existence to check.</li> 3609 <li><code>[out] result</code>: Whether the own property exists on the object or not.</li> 3610 </ul> 3611 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3612 <p>This API checks if the <code>Object</code> passed in has the named own property. <code>key</code> must 3613 be a <code>string</code> or a <code>symbol</code>, or an error will be thrown. Node-API will not 3614 perform any conversion between data types.</p> 3615 <h5>napi_set_named_property<span><a class="mark" href="#n_api_napi_set_named_property" id="n_api_napi_set_named_property">#</a></span></h5> 3616 <div class="api_metadata"> 3617 <span>Added in: v8.0.0</span> 3618 <span>N-API version: 1</span> 3619 </div> 3620 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_named_property</span><span class="hljs-params">(napi_env env, 3621 napi_value object, 3622 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8Name, 3623 napi_value value)</span>;</code></pre> 3624 <ul> 3625 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3626 <li><code>[in] object</code>: The object on which to set the property.</li> 3627 <li><code>[in] utf8Name</code>: The name of the property to set.</li> 3628 <li><code>[in] value</code>: The property value.</li> 3629 </ul> 3630 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3631 <p>This method is equivalent to calling <a href="#n_api_napi_set_property"><code>napi_set_property</code></a> with a <code>napi_value</code> 3632 created from the string passed in as <code>utf8Name</code>.</p> 3633 <h5>napi_get_named_property<span><a class="mark" href="#n_api_napi_get_named_property" id="n_api_napi_get_named_property">#</a></span></h5> 3634 <div class="api_metadata"> 3635 <span>Added in: v8.0.0</span> 3636 <span>N-API version: 1</span> 3637 </div> 3638 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_named_property</span><span class="hljs-params">(napi_env env, 3639 napi_value object, 3640 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8Name, 3641 napi_value* result)</span>;</code></pre> 3642 <ul> 3643 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3644 <li><code>[in] object</code>: The object from which to retrieve the property.</li> 3645 <li><code>[in] utf8Name</code>: The name of the property to get.</li> 3646 <li><code>[out] result</code>: The value of the property.</li> 3647 </ul> 3648 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3649 <p>This method is equivalent to calling <a href="#n_api_napi_get_property"><code>napi_get_property</code></a> with a <code>napi_value</code> 3650 created from the string passed in as <code>utf8Name</code>.</p> 3651 <h5>napi_has_named_property<span><a class="mark" href="#n_api_napi_has_named_property" id="n_api_napi_has_named_property">#</a></span></h5> 3652 <div class="api_metadata"> 3653 <span>Added in: v8.0.0</span> 3654 <span>N-API version: 1</span> 3655 </div> 3656 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_named_property</span><span class="hljs-params">(napi_env env, 3657 napi_value object, 3658 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8Name, 3659 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3660 <ul> 3661 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3662 <li><code>[in] object</code>: The object to query.</li> 3663 <li><code>[in] utf8Name</code>: The name of the property whose existence to check.</li> 3664 <li><code>[out] result</code>: Whether the property exists on the object or not.</li> 3665 </ul> 3666 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3667 <p>This method is equivalent to calling <a href="#n_api_napi_has_property"><code>napi_has_property</code></a> with a <code>napi_value</code> 3668 created from the string passed in as <code>utf8Name</code>.</p> 3669 <h5>napi_set_element<span><a class="mark" href="#n_api_napi_set_element" id="n_api_napi_set_element">#</a></span></h5> 3670 <div class="api_metadata"> 3671 <span>Added in: v8.0.0</span> 3672 <span>N-API version: 1</span> 3673 </div> 3674 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_element</span><span class="hljs-params">(napi_env env, 3675 napi_value object, 3676 <span class="hljs-type">uint32_t</span> index, 3677 napi_value value)</span>;</code></pre> 3678 <ul> 3679 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3680 <li><code>[in] object</code>: The object from which to set the properties.</li> 3681 <li><code>[in] index</code>: The index of the property to set.</li> 3682 <li><code>[in] value</code>: The property value.</li> 3683 </ul> 3684 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3685 <p>This API sets and element on the <code>Object</code> passed in.</p> 3686 <h5>napi_get_element<span><a class="mark" href="#n_api_napi_get_element" id="n_api_napi_get_element">#</a></span></h5> 3687 <div class="api_metadata"> 3688 <span>Added in: v8.0.0</span> 3689 <span>N-API version: 1</span> 3690 </div> 3691 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_element</span><span class="hljs-params">(napi_env env, 3692 napi_value object, 3693 <span class="hljs-type">uint32_t</span> index, 3694 napi_value* result)</span>;</code></pre> 3695 <ul> 3696 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3697 <li><code>[in] object</code>: The object from which to retrieve the property.</li> 3698 <li><code>[in] index</code>: The index of the property to get.</li> 3699 <li><code>[out] result</code>: The value of the property.</li> 3700 </ul> 3701 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3702 <p>This API gets the element at the requested index.</p> 3703 <h5>napi_has_element<span><a class="mark" href="#n_api_napi_has_element" id="n_api_napi_has_element">#</a></span></h5> 3704 <div class="api_metadata"> 3705 <span>Added in: v8.0.0</span> 3706 <span>N-API version: 1</span> 3707 </div> 3708 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_element</span><span class="hljs-params">(napi_env env, 3709 napi_value object, 3710 <span class="hljs-type">uint32_t</span> index, 3711 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3712 <ul> 3713 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3714 <li><code>[in] object</code>: The object to query.</li> 3715 <li><code>[in] index</code>: The index of the property whose existence to check.</li> 3716 <li><code>[out] result</code>: Whether the property exists on the object or not.</li> 3717 </ul> 3718 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3719 <p>This API returns if the <code>Object</code> passed in has an element at the 3720 requested index.</p> 3721 <h5>napi_delete_element<span><a class="mark" href="#n_api_napi_delete_element" id="n_api_napi_delete_element">#</a></span></h5> 3722 <div class="api_metadata"> 3723 <span>Added in: v8.2.0</span> 3724 <span>N-API version: 1</span> 3725 </div> 3726 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_delete_element</span><span class="hljs-params">(napi_env env, 3727 napi_value object, 3728 <span class="hljs-type">uint32_t</span> index, 3729 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3730 <ul> 3731 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3732 <li><code>[in] object</code>: The object to query.</li> 3733 <li><code>[in] index</code>: The index of the property to delete.</li> 3734 <li><code>[out] result</code>: Whether the element deletion succeeded or not. <code>result</code> can 3735 optionally be ignored by passing <code>NULL</code>.</li> 3736 </ul> 3737 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3738 <p>This API attempts to delete the specified <code>index</code> from <code>object</code>.</p> 3739 <h5>napi_define_properties<span><a class="mark" href="#n_api_napi_define_properties" id="n_api_napi_define_properties">#</a></span></h5> 3740 <div class="api_metadata"> 3741 <span>Added in: v8.0.0</span> 3742 <span>N-API version: 1</span> 3743 </div> 3744 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_define_properties</span><span class="hljs-params">(napi_env env, 3745 napi_value object, 3746 <span class="hljs-type">size_t</span> property_count, 3747 <span class="hljs-keyword">const</span> napi_property_descriptor* properties)</span>;</code></pre> 3748 <ul> 3749 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3750 <li><code>[in] object</code>: The object from which to retrieve the properties.</li> 3751 <li><code>[in] property_count</code>: The number of elements in the <code>properties</code> array.</li> 3752 <li><code>[in] properties</code>: The array of property descriptors.</li> 3753 </ul> 3754 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3755 <p>This method allows the efficient definition of multiple properties on a given 3756 object. The properties are defined using property descriptors (see 3757 <a href="#n_api_napi_property_descriptor"><code>napi_property_descriptor</code></a>). Given an array of such property descriptors, 3758 this API will set the properties on the object one at a time, as defined by 3759 <code>DefineOwnProperty()</code> (described in <a href="https://tc39.github.io/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots-defineownproperty-p-desc">Section 9.1.6</a> of the ECMA-262 3760 specification).</p> 3761 <h5>napi_object_freeze<span><a class="mark" href="#n_api_napi_object_freeze" id="n_api_napi_object_freeze">#</a></span></h5> 3762 <div class="api_metadata"> 3763 <span>Added in: v14.14.0, v12.20.0</span> 3764 <span>N-API version: 8</span> 3765 </div> 3766 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_object_freeze</span><span class="hljs-params">(napi_env env, 3767 napi_value object)</span>;</code></pre> 3768 <ul> 3769 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3770 <li><code>[in] object</code>: The object to freeze.</li> 3771 </ul> 3772 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3773 <p>This method freezes a given object. This prevents new properties from 3774 being added to it, existing properties from being removed, prevents 3775 changing the enumerability, configurability, or writability of existing 3776 properties, and prevents the values of existing properties from being changed. 3777 It also prevents the object's prototype from being changed. This is described 3778 in <a href="https://tc39.es/ecma262/#sec-object.freeze">Section 19.1.2.6</a> of the 3779 ECMA-262 specification.</p> 3780 <h5>napi_object_seal<span><a class="mark" href="#n_api_napi_object_seal" id="n_api_napi_object_seal">#</a></span></h5> 3781 <div class="api_metadata"> 3782 <span>Added in: v14.14.0, v12.20.0</span> 3783 <span>N-API version: 8</span> 3784 </div> 3785 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_object_seal</span><span class="hljs-params">(napi_env env, 3786 napi_value object)</span>;</code></pre> 3787 <ul> 3788 <li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3789 <li><code>[in] object</code>: The object to seal.</li> 3790 </ul> 3791 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3792 <p>This method seals a given object. This prevents new properties from being 3793 added to it, as well as marking all existing properties as non-configurable. 3794 This is described in <a href="https://tc39.es/ecma262/#sec-object.seal">Section 19.1.2.20</a> 3795 of the ECMA-262 specification.</p> 3796 </section><section><h3>Working with JavaScript functions<span><a class="mark" href="#n_api_working_with_javascript_functions" id="n_api_working_with_javascript_functions">#</a></span></h3> 3797 <p>Node-API provides a set of APIs that allow JavaScript code to 3798 call back into native code. Node-APIs that support calling back 3799 into native code take in a callback functions represented by 3800 the <code>napi_callback</code> type. When the JavaScript VM calls back to 3801 native code, the <code>napi_callback</code> function provided is invoked. The APIs 3802 documented in this section allow the callback function to do the 3803 following:</p> 3804 <ul> 3805 <li>Get information about the context in which the callback was invoked.</li> 3806 <li>Get the arguments passed into the callback.</li> 3807 <li>Return a <code>napi_value</code> back from the callback.</li> 3808 </ul> 3809 <p>Additionally, Node-API provides a set of functions which allow calling 3810 JavaScript functions from native code. One can either call a function 3811 like a regular JavaScript function call, or as a constructor 3812 function.</p> 3813 <p>Any non-<code>NULL</code> data which is passed to this API via the <code>data</code> field of the 3814 <code>napi_property_descriptor</code> items can be associated with <code>object</code> and freed 3815 whenever <code>object</code> is garbage-collected by passing both <code>object</code> and the data to 3816 <a href="#n_api_napi_add_finalizer"><code>napi_add_finalizer</code></a>.</p> 3817 <h4>napi_call_function<span><a class="mark" href="#n_api_napi_call_function" id="n_api_napi_call_function">#</a></span></h4> 3818 <div class="api_metadata"> 3819 <span>Added in: v8.0.0</span> 3820 <span>N-API version: 1</span> 3821 </div> 3822 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_call_function</span><span class="hljs-params">(napi_env env, 3823 napi_value recv, 3824 napi_value func, 3825 <span class="hljs-type">size_t</span> argc, 3826 <span class="hljs-keyword">const</span> napi_value* argv, 3827 napi_value* result)</span>;</code></pre> 3828 <ul> 3829 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3830 <li><code>[in] recv</code>: The <code>this</code> value passed to the called function.</li> 3831 <li><code>[in] func</code>: <code>napi_value</code> representing the JavaScript function to be invoked.</li> 3832 <li><code>[in] argc</code>: The count of elements in the <code>argv</code> array.</li> 3833 <li><code>[in] argv</code>: Array of <code>napi_values</code> representing JavaScript values passed in 3834 as arguments to the function.</li> 3835 <li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript object returned.</li> 3836 </ul> 3837 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3838 <p>This method allows a JavaScript function object to be called from a native 3839 add-on. This is the primary mechanism of calling back <em>from</em> the add-on's 3840 native code <em>into</em> JavaScript. For the special case of calling into JavaScript 3841 after an async operation, see <a href="#n_api_napi_make_callback"><code>napi_make_callback</code></a>.</p> 3842 <p>A sample use case might look as follows. Consider the following JavaScript 3843 snippet:</p> 3844 <pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">AddTwo</span>(<span class="hljs-params">num</span>) { 3845 <span class="hljs-keyword">return</span> num + <span class="hljs-number">2</span>; 3846 }</code></pre> 3847 <p>Then, the above function can be invoked from a native add-on using the 3848 following code:</p> 3849 <pre><code class="language-c"><span class="hljs-comment">// Get the function named "AddTwo" on the global object</span> 3850 napi_value global, add_two, arg; 3851 napi_status status = napi_get_global(env, &global); 3852 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3853 3854 status = napi_get_named_property(env, global, <span class="hljs-string">"AddTwo"</span>, &add_two); 3855 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3856 3857 <span class="hljs-comment">// const arg = 1337</span> 3858 status = napi_create_int32(env, <span class="hljs-number">1337</span>, &arg); 3859 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3860 3861 napi_value* argv = &arg; 3862 <span class="hljs-type">size_t</span> argc = <span class="hljs-number">1</span>; 3863 3864 <span class="hljs-comment">// AddTwo(arg);</span> 3865 napi_value return_val; 3866 status = napi_call_function(env, global, add_two, argc, argv, &return_val); 3867 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3868 3869 <span class="hljs-comment">// Convert the result back to a native type</span> 3870 <span class="hljs-type">int32_t</span> result; 3871 status = napi_get_value_int32(env, return_val, &result); 3872 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>;</code></pre> 3873 <h4>napi_create_function<span><a class="mark" href="#n_api_napi_create_function" id="n_api_napi_create_function">#</a></span></h4> 3874 <div class="api_metadata"> 3875 <span>Added in: v8.0.0</span> 3876 <span>N-API version: 1</span> 3877 </div> 3878 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_function</span><span class="hljs-params">(napi_env env, 3879 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8name, 3880 <span class="hljs-type">size_t</span> length, 3881 napi_callback cb, 3882 <span class="hljs-type">void</span>* data, 3883 napi_value* result)</span>;</code></pre> 3884 <ul> 3885 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3886 <li><code>[in] utf8Name</code>: The name of the function encoded as UTF8. This is visible 3887 within JavaScript as the new function object's <code>name</code> property.</li> 3888 <li><code>[in] length</code>: The length of the <code>utf8name</code> in bytes, or <code>NAPI_AUTO_LENGTH</code> if 3889 it is null-terminated.</li> 3890 <li><code>[in] cb</code>: The native function which should be called when this function 3891 object is invoked. <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3892 <li><code>[in] data</code>: User-provided data context. This will be passed back into the 3893 function when invoked later.</li> 3894 <li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript function object for 3895 the newly created function.</li> 3896 </ul> 3897 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3898 <p>This API allows an add-on author to create a function object in native code. 3899 This is the primary mechanism to allow calling <em>into</em> the add-on's native code 3900 <em>from</em> JavaScript.</p> 3901 <p>The newly created function is not automatically visible from script after this 3902 call. Instead, a property must be explicitly set on any object that is visible 3903 to JavaScript, in order for the function to be accessible from script.</p> 3904 <p>In order to expose a function as part of the 3905 add-on's module exports, set the newly created function on the exports 3906 object. A sample module might look as follows:</p> 3907 <pre><code class="language-c">napi_value <span class="hljs-title function_">SayHello</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 3908 <span class="hljs-built_in">printf</span>(<span class="hljs-string">"Hello\n"</span>); 3909 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 3910 } 3911 3912 napi_value <span class="hljs-title function_">Init</span><span class="hljs-params">(napi_env env, napi_value exports)</span> { 3913 napi_status status; 3914 3915 napi_value fn; 3916 status = napi_create_function(env, <span class="hljs-literal">NULL</span>, <span class="hljs-number">0</span>, SayHello, <span class="hljs-literal">NULL</span>, &fn); 3917 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 3918 3919 status = napi_set_named_property(env, exports, <span class="hljs-string">"sayHello"</span>, fn); 3920 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 3921 3922 <span class="hljs-keyword">return</span> exports; 3923 } 3924 3925 NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)</code></pre> 3926 <p>Given the above code, the add-on can be used from JavaScript as follows:</p> 3927 <pre><code class="language-js"><span class="hljs-keyword">const</span> myaddon = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./addon'</span>); 3928 myaddon.<span class="hljs-title function_">sayHello</span>();</code></pre> 3929 <p>The string passed to <code>require()</code> is the name of the target in <code>binding.gyp</code> 3930 responsible for creating the <code>.node</code> file.</p> 3931 <p>Any non-<code>NULL</code> data which is passed to this API via the <code>data</code> parameter can 3932 be associated with the resulting JavaScript function (which is returned in the 3933 <code>result</code> parameter) and freed whenever the function is garbage-collected by 3934 passing both the JavaScript function and the data to <a href="#n_api_napi_add_finalizer"><code>napi_add_finalizer</code></a>.</p> 3935 <p>JavaScript <code>Function</code>s are described in <a href="https://tc39.github.io/ecma262/#sec-function-objects">Section 19.2</a> of the ECMAScript 3936 Language Specification.</p> 3937 <h4>napi_get_cb_info<span><a class="mark" href="#n_api_napi_get_cb_info" id="n_api_napi_get_cb_info">#</a></span></h4> 3938 <div class="api_metadata"> 3939 <span>Added in: v8.0.0</span> 3940 <span>N-API version: 1</span> 3941 </div> 3942 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_cb_info</span><span class="hljs-params">(napi_env env, 3943 napi_callback_info cbinfo, 3944 <span class="hljs-type">size_t</span>* argc, 3945 napi_value* argv, 3946 napi_value* thisArg, 3947 <span class="hljs-type">void</span>** data)</span></code></pre> 3948 <ul> 3949 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3950 <li><code>[in] cbinfo</code>: The callback info passed into the callback function.</li> 3951 <li><code>[in-out] argc</code>: Specifies the length of the provided <code>argv</code> array and 3952 receives the actual count of arguments.</li> 3953 <li><code>[out] argv</code>: Buffer to which the <code>napi_value</code> representing the arguments are 3954 copied. If there are more arguments than the provided count, only the 3955 requested number of arguments are copied. If there are fewer arguments 3956 provided than claimed, the rest of <code>argv</code> is filled with <code>napi_value</code> values 3957 that represent <code>undefined</code>.</li> 3958 <li><code>[out] this</code>: Receives the JavaScript <code>this</code> argument for the call.</li> 3959 <li><code>[out] data</code>: Receives the data pointer for the callback.</li> 3960 </ul> 3961 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3962 <p>This method is used within a callback function to retrieve details about the 3963 call like the arguments and the <code>this</code> pointer from a given callback info.</p> 3964 <h4>napi_get_new_target<span><a class="mark" href="#n_api_napi_get_new_target" id="n_api_napi_get_new_target">#</a></span></h4> 3965 <div class="api_metadata"> 3966 <span>Added in: v8.6.0</span> 3967 <span>N-API version: 1</span> 3968 </div> 3969 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_new_target</span><span class="hljs-params">(napi_env env, 3970 napi_callback_info cbinfo, 3971 napi_value* result)</span></code></pre> 3972 <ul> 3973 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3974 <li><code>[in] cbinfo</code>: The callback info passed into the callback function.</li> 3975 <li><code>[out] result</code>: The <code>new.target</code> of the constructor call.</li> 3976 </ul> 3977 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 3978 <p>This API returns the <code>new.target</code> of the constructor call. If the current 3979 callback is not a constructor call, the result is <code>NULL</code>.</p> 3980 <h4>napi_new_instance<span><a class="mark" href="#n_api_napi_new_instance" id="n_api_napi_new_instance">#</a></span></h4> 3981 <div class="api_metadata"> 3982 <span>Added in: v8.0.0</span> 3983 <span>N-API version: 1</span> 3984 </div> 3985 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_new_instance</span><span class="hljs-params">(napi_env env, 3986 napi_value cons, 3987 <span class="hljs-type">size_t</span> argc, 3988 napi_value* argv, 3989 napi_value* result)</span></code></pre> 3990 <ul> 3991 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 3992 <li><code>[in] cons</code>: <code>napi_value</code> representing the JavaScript function to be invoked 3993 as a constructor.</li> 3994 <li><code>[in] argc</code>: The count of elements in the <code>argv</code> array.</li> 3995 <li><code>[in] argv</code>: Array of JavaScript values as <code>napi_value</code> representing the 3996 arguments to the constructor.</li> 3997 <li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript object returned, 3998 which in this case is the constructed object.</li> 3999 </ul> 4000 <p>This method is used to instantiate a new JavaScript value using a given 4001 <code>napi_value</code> that represents the constructor for the object. For example, 4002 consider the following snippet:</p> 4003 <pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">MyObject</span>(<span class="hljs-params">param</span>) { 4004 <span class="hljs-variable language_">this</span>.<span class="hljs-property">param</span> = param; 4005 } 4006 4007 <span class="hljs-keyword">const</span> arg = <span class="hljs-string">'hello'</span>; 4008 <span class="hljs-keyword">const</span> value = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyObject</span>(arg);</code></pre> 4009 <p>The following can be approximated in Node-API using the following snippet:</p> 4010 <pre><code class="language-c"><span class="hljs-comment">// Get the constructor function MyObject</span> 4011 napi_value global, constructor, arg, value; 4012 napi_status status = napi_get_global(env, &global); 4013 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 4014 4015 status = napi_get_named_property(env, global, <span class="hljs-string">"MyObject"</span>, &constructor); 4016 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 4017 4018 <span class="hljs-comment">// const arg = "hello"</span> 4019 status = napi_create_string_utf8(env, <span class="hljs-string">"hello"</span>, NAPI_AUTO_LENGTH, &arg); 4020 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 4021 4022 napi_value* argv = &arg; 4023 <span class="hljs-type">size_t</span> argc = <span class="hljs-number">1</span>; 4024 4025 <span class="hljs-comment">// const value = new MyObject(arg)</span> 4026 status = napi_new_instance(env, constructor, argc, argv, &value);</code></pre> 4027 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4028 </section><section><h3>Object wrap<span><a class="mark" href="#n_api_object_wrap" id="n_api_object_wrap">#</a></span></h3> 4029 <p>Node-API offers a way to "wrap" C++ classes and instances so that the class 4030 constructor and methods can be called from JavaScript.</p> 4031 <ol> 4032 <li>The <a href="#n_api_napi_define_class"><code>napi_define_class</code></a> API defines a JavaScript class with constructor, 4033 static properties and methods, and instance properties and methods that 4034 correspond to the C++ class.</li> 4035 <li>When JavaScript code invokes the constructor, the constructor callback 4036 uses <a href="#n_api_napi_wrap"><code>napi_wrap</code></a> to wrap a new C++ instance in a JavaScript object, 4037 then returns the wrapper object.</li> 4038 <li>When JavaScript code invokes a method or property accessor on the class, 4039 the corresponding <code>napi_callback</code> C++ function is invoked. For an instance 4040 callback, <a href="#n_api_napi_unwrap"><code>napi_unwrap</code></a> obtains the C++ instance that is the target of 4041 the call.</li> 4042 </ol> 4043 <p>For wrapped objects it may be difficult to distinguish between a function 4044 called on a class prototype and a function called on an instance of a class. 4045 A common pattern used to address this problem is to save a persistent 4046 reference to the class constructor for later <code>instanceof</code> checks.</p> 4047 <pre><code class="language-c">napi_value MyClass_constructor = <span class="hljs-literal">NULL</span>; 4048 status = napi_get_reference_value(env, MyClass::es_constructor, &MyClass_constructor); 4049 assert(napi_ok == status); 4050 <span class="hljs-type">bool</span> is_instance = <span class="hljs-literal">false</span>; 4051 status = napi_instanceof(env, es_this, MyClass_constructor, &is_instance); 4052 assert(napi_ok == status); 4053 <span class="hljs-keyword">if</span> (is_instance) { 4054 <span class="hljs-comment">// napi_unwrap() ...</span> 4055 } <span class="hljs-keyword">else</span> { 4056 <span class="hljs-comment">// otherwise...</span> 4057 }</code></pre> 4058 <p>The reference must be freed once it is no longer needed.</p> 4059 <p>There are occasions where <code>napi_instanceof()</code> is insufficient for ensuring that 4060 a JavaScript object is a wrapper for a certain native type. This is the case 4061 especially when wrapped JavaScript objects are passed back into the addon via 4062 static methods rather than as the <code>this</code> value of prototype methods. In such 4063 cases there is a chance that they may be unwrapped incorrectly.</p> 4064 <pre><code class="language-js"><span class="hljs-keyword">const</span> myAddon = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./build/Release/my_addon.node'</span>); 4065 4066 <span class="hljs-comment">// `openDatabase()` returns a JavaScript object that wraps a native database</span> 4067 <span class="hljs-comment">// handle.</span> 4068 <span class="hljs-keyword">const</span> dbHandle = myAddon.<span class="hljs-title function_">openDatabase</span>(); 4069 4070 <span class="hljs-comment">// `query()` returns a JavaScript object that wraps a native query handle.</span> 4071 <span class="hljs-keyword">const</span> queryHandle = myAddon.<span class="hljs-title function_">query</span>(dbHandle, <span class="hljs-string">'Gimme ALL the things!'</span>); 4072 4073 <span class="hljs-comment">// There is an accidental error in the line below. The first parameter to</span> 4074 <span class="hljs-comment">// `myAddon.queryHasRecords()` should be the database handle (`dbHandle`), not</span> 4075 <span class="hljs-comment">// the query handle (`query`), so the correct condition for the while-loop</span> 4076 <span class="hljs-comment">// should be</span> 4077 <span class="hljs-comment">//</span> 4078 <span class="hljs-comment">// myAddon.queryHasRecords(dbHandle, queryHandle)</span> 4079 <span class="hljs-comment">//</span> 4080 <span class="hljs-keyword">while</span> (myAddon.<span class="hljs-title function_">queryHasRecords</span>(queryHandle, dbHandle)) { 4081 <span class="hljs-comment">// retrieve records</span> 4082 }</code></pre> 4083 <p>In the above example <code>myAddon.queryHasRecords()</code> is a method that accepts two 4084 arguments. The first is a database handle and the second is a query handle. 4085 Internally, it unwraps the first argument and casts the resulting pointer to a 4086 native database handle. It then unwraps the second argument and casts the 4087 resulting pointer to a query handle. If the arguments are passed in the wrong 4088 order, the casts will work, however, there is a good chance that the underlying 4089 database operation will fail, or will even cause an invalid memory access.</p> 4090 <p>To ensure that the pointer retrieved from the first argument is indeed a pointer 4091 to a database handle and, similarly, that the pointer retrieved from the second 4092 argument is indeed a pointer to a query handle, the implementation of 4093 <code>queryHasRecords()</code> has to perform a type validation. Retaining the JavaScript 4094 class constructor from which the database handle was instantiated and the 4095 constructor from which the query handle was instantiated in <code>napi_ref</code>s can 4096 help, because <code>napi_instanceof()</code> can then be used to ensure that the instances 4097 passed into <code>queryHashRecords()</code> are indeed of the correct type.</p> 4098 <p>Unfortunately, <code>napi_instanceof()</code> does not protect against prototype 4099 manipulation. For example, the prototype of the database handle instance can be 4100 set to the prototype of the constructor for query handle instances. In this 4101 case, the database handle instance can appear as a query handle instance, and it 4102 will pass the <code>napi_instanceof()</code> test for a query handle instance, while still 4103 containing a pointer to a database handle.</p> 4104 <p>To this end, Node-API provides type-tagging capabilities.</p> 4105 <p>A type tag is a 128-bit integer unique to the addon. Node-API provides the 4106 <code>napi_type_tag</code> structure for storing a type tag. When such a value is passed 4107 along with a JavaScript object stored in a <code>napi_value</code> to 4108 <code>napi_type_tag_object()</code>, the JavaScript object will be "marked" with the 4109 type tag. The "mark" is invisible on the JavaScript side. When a JavaScript 4110 object arrives into a native binding, <code>napi_check_object_type_tag()</code> can be used 4111 along with the original type tag to determine whether the JavaScript object was 4112 previously "marked" with the type tag. This creates a type-checking capability 4113 of a higher fidelity than <code>napi_instanceof()</code> can provide, because such type- 4114 tagging survives prototype manipulation and addon unloading/reloading.</p> 4115 <p>Continuing the above example, the following skeleton addon implementation 4116 illustrates the use of <code>napi_type_tag_object()</code> and 4117 <code>napi_check_object_type_tag()</code>.</p> 4118 <pre><code class="language-c"><span class="hljs-comment">// This value is the type tag for a database handle. The command</span> 4119 <span class="hljs-comment">//</span> 4120 <span class="hljs-comment">// uuidgen | sed -r -e 's/-//g' -e 's/(.{16})(.*)/0x\1, 0x\2/'</span> 4121 <span class="hljs-comment">//</span> 4122 <span class="hljs-comment">// can be used to obtain the two values with which to initialize the structure.</span> 4123 <span class="hljs-keyword">static</span> <span class="hljs-keyword">const</span> napi_type_tag DatabaseHandleTypeTag = { 4124 <span class="hljs-number">0x1edf75a38336451d</span>, <span class="hljs-number">0xa5ed9ce2e4c00c38</span> 4125 }; 4126 4127 <span class="hljs-comment">// This value is the type tag for a query handle.</span> 4128 <span class="hljs-keyword">static</span> <span class="hljs-keyword">const</span> napi_type_tag QueryHandleTypeTag = { 4129 <span class="hljs-number">0x9c73317f9fad44a3</span>, <span class="hljs-number">0x93c3920bf3b0ad6a</span> 4130 }; 4131 4132 <span class="hljs-keyword">static</span> napi_value 4133 <span class="hljs-title function_">openDatabase</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 4134 napi_status status; 4135 napi_value result; 4136 4137 <span class="hljs-comment">// Perform the underlying action which results in a database handle.</span> 4138 DatabaseHandle* dbHandle = open_database(); 4139 4140 <span class="hljs-comment">// Create a new, empty JS object.</span> 4141 status = napi_create_object(env, &result); 4142 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4143 4144 <span class="hljs-comment">// Tag the object to indicate that it holds a pointer to a `DatabaseHandle`.</span> 4145 status = napi_type_tag_object(env, result, &DatabaseHandleTypeTag); 4146 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4147 4148 <span class="hljs-comment">// Store the pointer to the `DatabaseHandle` structure inside the JS object.</span> 4149 status = napi_wrap(env, result, dbHandle, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>); 4150 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4151 4152 <span class="hljs-keyword">return</span> result; 4153 } 4154 4155 <span class="hljs-comment">// Later when we receive a JavaScript object purporting to be a database handle</span> 4156 <span class="hljs-comment">// we can use `napi_check_object_type_tag()` to ensure that it is indeed such a</span> 4157 <span class="hljs-comment">// handle.</span> 4158 4159 <span class="hljs-keyword">static</span> napi_value 4160 <span class="hljs-title function_">query</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 4161 napi_status status; 4162 <span class="hljs-type">size_t</span> argc = <span class="hljs-number">2</span>; 4163 napi_value argv[<span class="hljs-number">2</span>]; 4164 <span class="hljs-type">bool</span> is_db_handle; 4165 4166 status = napi_get_cb_info(env, info, &argc, argv, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>); 4167 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4168 4169 <span class="hljs-comment">// Check that the object passed as the first parameter has the previously</span> 4170 <span class="hljs-comment">// applied tag.</span> 4171 status = napi_check_object_type_tag(env, 4172 argv[<span class="hljs-number">0</span>], 4173 &DatabaseHandleTypeTag, 4174 &is_db_handle); 4175 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4176 4177 <span class="hljs-comment">// Throw a `TypeError` if it doesn't.</span> 4178 <span class="hljs-keyword">if</span> (!is_db_handle) { 4179 <span class="hljs-comment">// Throw a TypeError.</span> 4180 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4181 } 4182 }</code></pre> 4183 <h4>napi_define_class<span><a class="mark" href="#n_api_napi_define_class" id="n_api_napi_define_class">#</a></span></h4> 4184 <div class="api_metadata"> 4185 <span>Added in: v8.0.0</span> 4186 <span>N-API version: 1</span> 4187 </div> 4188 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_define_class</span><span class="hljs-params">(napi_env env, 4189 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8name, 4190 <span class="hljs-type">size_t</span> length, 4191 napi_callback constructor, 4192 <span class="hljs-type">void</span>* data, 4193 <span class="hljs-type">size_t</span> property_count, 4194 <span class="hljs-keyword">const</span> napi_property_descriptor* properties, 4195 napi_value* result)</span>;</code></pre> 4196 <ul> 4197 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4198 <li><code>[in] utf8name</code>: Name of the JavaScript constructor function; When wrapping a 4199 C++ class, we recommend for clarity that this name be the same as that of 4200 the C++ class.</li> 4201 <li><code>[in] length</code>: The length of the <code>utf8name</code> in bytes, or <code>NAPI_AUTO_LENGTH</code> 4202 if it is null-terminated.</li> 4203 <li><code>[in] constructor</code>: Callback function that handles constructing instances 4204 of the class. When wrapping a C++ class, this method must be a static member 4205 with the <a href="#n_api_napi_callback"><code>napi_callback</code></a> signature. A C++ class constructor cannot be 4206 used. <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 4207 <li><code>[in] data</code>: Optional data to be passed to the constructor callback as 4208 the <code>data</code> property of the callback info.</li> 4209 <li><code>[in] property_count</code>: Number of items in the <code>properties</code> array argument.</li> 4210 <li><code>[in] properties</code>: Array of property descriptors describing static and 4211 instance data properties, accessors, and methods on the class 4212 See <code>napi_property_descriptor</code>.</li> 4213 <li><code>[out] result</code>: A <code>napi_value</code> representing the constructor function for 4214 the class.</li> 4215 </ul> 4216 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4217 <p>Defines a JavaScript class, including:</p> 4218 <ul> 4219 <li>A JavaScript constructor function that has the class name. When wrapping a 4220 corresponding C++ class, the callback passed via <code>constructor</code> can be used to 4221 instantiate a new C++ class instance, which can then be placed inside the 4222 JavaScript object instance being constructed using <a href="#n_api_napi_wrap"><code>napi_wrap</code></a>.</li> 4223 <li>Properties on the constructor function whose implementation can call 4224 corresponding <em>static</em> data properties, accessors, and methods of the C++ 4225 class (defined by property descriptors with the <code>napi_static</code> attribute).</li> 4226 <li>Properties on the constructor function's <code>prototype</code> object. When wrapping a 4227 C++ class, <em>non-static</em> data properties, accessors, and methods of the C++ 4228 class can be called from the static functions given in the property 4229 descriptors without the <code>napi_static</code> attribute after retrieving the C++ class 4230 instance placed inside the JavaScript object instance by using 4231 <a href="#n_api_napi_unwrap"><code>napi_unwrap</code></a>.</li> 4232 </ul> 4233 <p>When wrapping a C++ class, the C++ constructor callback passed via <code>constructor</code> 4234 should be a static method on the class that calls the actual class constructor, 4235 then wraps the new C++ instance in a JavaScript object, and returns the wrapper 4236 object. See <a href="#n_api_napi_wrap"><code>napi_wrap</code></a> for details.</p> 4237 <p>The JavaScript constructor function returned from <a href="#n_api_napi_define_class"><code>napi_define_class</code></a> is 4238 often saved and used later to construct new instances of the class from native 4239 code, and/or to check whether provided values are instances of the class. In 4240 that case, to prevent the function value from being garbage-collected, a 4241 strong persistent reference to it can be created using 4242 <a href="#n_api_napi_create_reference"><code>napi_create_reference</code></a>, ensuring that the reference count is kept >= 1.</p> 4243 <p>Any non-<code>NULL</code> data which is passed to this API via the <code>data</code> parameter or via 4244 the <code>data</code> field of the <code>napi_property_descriptor</code> array items can be associated 4245 with the resulting JavaScript constructor (which is returned in the <code>result</code> 4246 parameter) and freed whenever the class is garbage-collected by passing both 4247 the JavaScript function and the data to <a href="#n_api_napi_add_finalizer"><code>napi_add_finalizer</code></a>.</p> 4248 <h4>napi_wrap<span><a class="mark" href="#n_api_napi_wrap" id="n_api_napi_wrap">#</a></span></h4> 4249 <div class="api_metadata"> 4250 <span>Added in: v8.0.0</span> 4251 <span>N-API version: 1</span> 4252 </div> 4253 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_wrap</span><span class="hljs-params">(napi_env env, 4254 napi_value js_object, 4255 <span class="hljs-type">void</span>* native_object, 4256 napi_finalize finalize_cb, 4257 <span class="hljs-type">void</span>* finalize_hint, 4258 napi_ref* result)</span>;</code></pre> 4259 <ul> 4260 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4261 <li><code>[in] js_object</code>: The JavaScript object that will be the wrapper for the 4262 native object.</li> 4263 <li><code>[in] native_object</code>: The native instance that will be wrapped in the 4264 JavaScript object.</li> 4265 <li><code>[in] finalize_cb</code>: Optional native callback that can be used to free the 4266 native instance when the JavaScript object is ready for garbage-collection. 4267 <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 4268 <li><code>[in] finalize_hint</code>: Optional contextual hint that is passed to the 4269 finalize callback.</li> 4270 <li><code>[out] result</code>: Optional reference to the wrapped object.</li> 4271 </ul> 4272 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4273 <p>Wraps a native instance in a JavaScript object. The native instance can be 4274 retrieved later using <code>napi_unwrap()</code>.</p> 4275 <p>When JavaScript code invokes a constructor for a class that was defined using 4276 <code>napi_define_class()</code>, the <code>napi_callback</code> for the constructor is invoked. 4277 After constructing an instance of the native class, the callback must then call 4278 <code>napi_wrap()</code> to wrap the newly constructed instance in the already-created 4279 JavaScript object that is the <code>this</code> argument to the constructor callback. 4280 (That <code>this</code> object was created from the constructor function's <code>prototype</code>, 4281 so it already has definitions of all the instance properties and methods.)</p> 4282 <p>Typically when wrapping a class instance, a finalize callback should be 4283 provided that simply deletes the native instance that is received as the <code>data</code> 4284 argument to the finalize callback.</p> 4285 <p>The optional returned reference is initially a weak reference, meaning it 4286 has a reference count of 0. Typically this reference count would be incremented 4287 temporarily during async operations that require the instance to remain valid.</p> 4288 <p><em>Caution</em>: The optional returned reference (if obtained) should be deleted via 4289 <a href="#n_api_napi_delete_reference"><code>napi_delete_reference</code></a> ONLY in response to the finalize callback 4290 invocation. If it is deleted before then, then the finalize callback may never 4291 be invoked. Therefore, when obtaining a reference a finalize callback is also 4292 required in order to enable correct disposal of the reference.</p> 4293 <p>Calling <code>napi_wrap()</code> a second time on an object will return an error. To 4294 associate another native instance with the object, use <code>napi_remove_wrap()</code> 4295 first.</p> 4296 <h4>napi_unwrap<span><a class="mark" href="#n_api_napi_unwrap" id="n_api_napi_unwrap">#</a></span></h4> 4297 <div class="api_metadata"> 4298 <span>Added in: v8.0.0</span> 4299 <span>N-API version: 1</span> 4300 </div> 4301 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_unwrap</span><span class="hljs-params">(napi_env env, 4302 napi_value js_object, 4303 <span class="hljs-type">void</span>** result)</span>;</code></pre> 4304 <ul> 4305 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4306 <li><code>[in] js_object</code>: The object associated with the native instance.</li> 4307 <li><code>[out] result</code>: Pointer to the wrapped native instance.</li> 4308 </ul> 4309 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4310 <p>Retrieves a native instance that was previously wrapped in a JavaScript 4311 object using <code>napi_wrap()</code>.</p> 4312 <p>When JavaScript code invokes a method or property accessor on the class, the 4313 corresponding <code>napi_callback</code> is invoked. If the callback is for an instance 4314 method or accessor, then the <code>this</code> argument to the callback is the wrapper 4315 object; the wrapped C++ instance that is the target of the call can be obtained 4316 then by calling <code>napi_unwrap()</code> on the wrapper object.</p> 4317 <h4>napi_remove_wrap<span><a class="mark" href="#n_api_napi_remove_wrap" id="n_api_napi_remove_wrap">#</a></span></h4> 4318 <div class="api_metadata"> 4319 <span>Added in: v8.5.0</span> 4320 <span>N-API version: 1</span> 4321 </div> 4322 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_remove_wrap</span><span class="hljs-params">(napi_env env, 4323 napi_value js_object, 4324 <span class="hljs-type">void</span>** result)</span>;</code></pre> 4325 <ul> 4326 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4327 <li><code>[in] js_object</code>: The object associated with the native instance.</li> 4328 <li><code>[out] result</code>: Pointer to the wrapped native instance.</li> 4329 </ul> 4330 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4331 <p>Retrieves a native instance that was previously wrapped in the JavaScript 4332 object <code>js_object</code> using <code>napi_wrap()</code> and removes the wrapping. If a finalize 4333 callback was associated with the wrapping, it will no longer be called when the 4334 JavaScript object becomes garbage-collected.</p> 4335 <h4>napi_type_tag_object<span><a class="mark" href="#n_api_napi_type_tag_object" id="n_api_napi_type_tag_object">#</a></span></h4> 4336 <div class="api_metadata"> 4337 <span>Added in: v14.8.0, v12.19.0</span> 4338 <span>N-API version: 8</span> 4339 </div> 4340 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_type_tag_object</span><span class="hljs-params">(napi_env env, 4341 napi_value js_object, 4342 <span class="hljs-keyword">const</span> napi_type_tag* type_tag)</span>;</code></pre> 4343 <ul> 4344 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4345 <li><code>[in] js_object</code>: The JavaScript object to be marked.</li> 4346 <li><code>[in] type_tag</code>: The tag with which the object is to be marked.</li> 4347 </ul> 4348 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4349 <p>Associates the value of the <code>type_tag</code> pointer with the JavaScript object. 4350 <code>napi_check_object_type_tag()</code> can then be used to compare the tag that was 4351 attached to the object with one owned by the addon to ensure that the object 4352 has the right type.</p> 4353 <p>If the object already has an associated type tag, this API will return 4354 <code>napi_invalid_arg</code>.</p> 4355 <h4>napi_check_object_type_tag<span><a class="mark" href="#n_api_napi_check_object_type_tag" id="n_api_napi_check_object_type_tag">#</a></span></h4> 4356 <div class="api_metadata"> 4357 <span>Added in: v14.8.0, v12.19.0</span> 4358 <span>N-API version: 8</span> 4359 </div> 4360 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_check_object_type_tag</span><span class="hljs-params">(napi_env env, 4361 napi_value js_object, 4362 <span class="hljs-keyword">const</span> napi_type_tag* type_tag, 4363 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 4364 <ul> 4365 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4366 <li><code>[in] js_object</code>: The JavaScript object whose type tag to examine.</li> 4367 <li><code>[in] type_tag</code>: The tag with which to compare any tag found on the object.</li> 4368 <li><code>[out] result</code>: Whether the type tag given matched the type tag on the 4369 object. <code>false</code> is also returned if no type tag was found on the object.</li> 4370 </ul> 4371 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4372 <p>Compares the pointer given as <code>type_tag</code> with any that can be found on 4373 <code>js_object</code>. If no tag is found on <code>js_object</code> or, if a tag is found but it does 4374 not match <code>type_tag</code>, then <code>result</code> is set to <code>false</code>. If a tag is found and it 4375 matches <code>type_tag</code>, then <code>result</code> is set to <code>true</code>.</p> 4376 <h4>napi_add_finalizer<span><a class="mark" href="#n_api_napi_add_finalizer" id="n_api_napi_add_finalizer">#</a></span></h4> 4377 <div class="api_metadata"> 4378 <span>Added in: v8.0.0</span> 4379 <span>N-API version: 5</span> 4380 </div> 4381 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_add_finalizer</span><span class="hljs-params">(napi_env env, 4382 napi_value js_object, 4383 <span class="hljs-type">void</span>* native_object, 4384 napi_finalize finalize_cb, 4385 <span class="hljs-type">void</span>* finalize_hint, 4386 napi_ref* result)</span>;</code></pre> 4387 <ul> 4388 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4389 <li><code>[in] js_object</code>: The JavaScript object to which the native data will be 4390 attached.</li> 4391 <li><code>[in] native_object</code>: The native data that will be attached to the JavaScript 4392 object.</li> 4393 <li><code>[in] finalize_cb</code>: Native callback that will be used to free the 4394 native data when the JavaScript object is ready for garbage-collection. 4395 <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 4396 <li><code>[in] finalize_hint</code>: Optional contextual hint that is passed to the 4397 finalize callback.</li> 4398 <li><code>[out] result</code>: Optional reference to the JavaScript object.</li> 4399 </ul> 4400 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4401 <p>Adds a <code>napi_finalize</code> callback which will be called when the JavaScript object 4402 in <code>js_object</code> is ready for garbage collection. This API is similar to 4403 <code>napi_wrap()</code> except that:</p> 4404 <ul> 4405 <li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 4406 <li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 4407 <li>the API can be called multiple times with different data items in order to 4408 attach each of them to the JavaScript object, and</li> 4409 <li>the object manipulated by the API can be used with <code>napi_wrap()</code>.</li> 4410 </ul> 4411 <p><em>Caution</em>: The optional returned reference (if obtained) should be deleted via 4412 <a href="#n_api_napi_delete_reference"><code>napi_delete_reference</code></a> ONLY in response to the finalize callback 4413 invocation. If it is deleted before then, then the finalize callback may never 4414 be invoked. Therefore, when obtaining a reference a finalize callback is also 4415 required in order to enable correct disposal of the reference.</p> 4416 </section><section><h3>Simple asynchronous operations<span><a class="mark" href="#n_api_simple_asynchronous_operations" id="n_api_simple_asynchronous_operations">#</a></span></h3> 4417 <p>Addon modules often need to leverage async helpers from libuv as part of their 4418 implementation. This allows them to schedule work to be executed asynchronously 4419 so that their methods can return in advance of the work being completed. This 4420 allows them to avoid blocking overall execution of the Node.js application.</p> 4421 <p>Node-API provides an ABI-stable interface for these 4422 supporting functions which covers the most common asynchronous use cases.</p> 4423 <p>Node-API defines the <code>napi_async_work</code> structure which is used to manage 4424 asynchronous workers. Instances are created/deleted with 4425 <a href="#n_api_napi_create_async_work"><code>napi_create_async_work</code></a> and <a href="#n_api_napi_delete_async_work"><code>napi_delete_async_work</code></a>.</p> 4426 <p>The <code>execute</code> and <code>complete</code> callbacks are functions that will be 4427 invoked when the executor is ready to execute and when it completes its 4428 task respectively.</p> 4429 <p>The <code>execute</code> function should avoid making any Node-API calls 4430 that could result in the execution of JavaScript or interaction with 4431 JavaScript objects. Most often, any code that needs to make Node-API 4432 calls should be made in <code>complete</code> callback instead. 4433 Avoid using the <code>napi_env</code> parameter in the execute callback as 4434 it will likely execute JavaScript.</p> 4435 <p>These functions implement the following interfaces:</p> 4436 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-title function_">void</span> <span class="hljs-params">(*napi_async_execute_callback)</span><span class="hljs-params">(napi_env env, 4437 <span class="hljs-type">void</span>* data)</span>; 4438 <span class="hljs-keyword">typedef</span> <span class="hljs-title function_">void</span> <span class="hljs-params">(*napi_async_complete_callback)</span><span class="hljs-params">(napi_env env, 4439 napi_status status, 4440 <span class="hljs-type">void</span>* data)</span>;</code></pre> 4441 <p>When these methods are invoked, the <code>data</code> parameter passed will be the 4442 addon-provided <code>void*</code> data that was passed into the 4443 <code>napi_create_async_work</code> call.</p> 4444 <p>Once created the async worker can be queued 4445 for execution using the <a href="#n_api_napi_queue_async_work"><code>napi_queue_async_work</code></a> function:</p> 4446 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_queue_async_work</span><span class="hljs-params">(napi_env env, 4447 napi_async_work work)</span>;</code></pre> 4448 <p><a href="#n_api_napi_cancel_async_work"><code>napi_cancel_async_work</code></a> can be used if the work needs 4449 to be cancelled before the work has started execution.</p> 4450 <p>After calling <a href="#n_api_napi_cancel_async_work"><code>napi_cancel_async_work</code></a>, the <code>complete</code> callback 4451 will be invoked with a status value of <code>napi_cancelled</code>. 4452 The work should not be deleted before the <code>complete</code> 4453 callback invocation, even when it was cancelled.</p> 4454 <h4>napi_create_async_work<span><a class="mark" href="#n_api_napi_create_async_work" id="n_api_napi_create_async_work">#</a></span></h4> 4455 <div class="api_metadata"> 4456 <details class="changelog"><summary>History</summary> 4457 <table> 4458 <tbody><tr><th>Version</th><th>Changes</th></tr> 4459 <tr><td>v8.6.0</td> 4460 <td><p>Added <code>async_resource</code> and <code>async_resource_name</code> parameters.</p></td></tr> 4461 <tr><td>v8.0.0</td> 4462 <td><p><span>Added in: v8.0.0</span></p></td></tr> 4463 </tbody></table> 4464 </details> 4465 <span>N-API version: 1</span> 4466 </div> 4467 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_async_work</span><span class="hljs-params">(napi_env env, 4468 napi_value async_resource, 4469 napi_value async_resource_name, 4470 napi_async_execute_callback execute, 4471 napi_async_complete_callback complete, 4472 <span class="hljs-type">void</span>* data, 4473 napi_async_work* result)</span>;</code></pre> 4474 <ul> 4475 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4476 <li><code>[in] async_resource</code>: An optional object associated with the async work 4477 that will be passed to possible <code>async_hooks</code> <a href="async_hooks.html#async_hooks_init_asyncid_type_triggerasyncid_resource"><code>init</code> hooks</a>.</li> 4478 <li><code>[in] async_resource_name</code>: Identifier for the kind of resource that is being 4479 provided for diagnostic information exposed by the <code>async_hooks</code> API.</li> 4480 <li><code>[in] execute</code>: The native function which should be called to execute the 4481 logic asynchronously. The given function is called from a worker pool thread 4482 and can execute in parallel with the main event loop thread.</li> 4483 <li><code>[in] complete</code>: The native function which will be called when the 4484 asynchronous logic is completed or is cancelled. The given function is called 4485 from the main event loop thread. <a href="#n_api_napi_async_complete_callback"><code>napi_async_complete_callback</code></a> provides 4486 more details.</li> 4487 <li><code>[in] data</code>: User-provided data context. This will be passed back into the 4488 execute and complete functions.</li> 4489 <li><code>[out] result</code>: <code>napi_async_work*</code> which is the handle to the newly created 4490 async work.</li> 4491 </ul> 4492 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4493 <p>This API allocates a work object that is used to execute logic asynchronously. 4494 It should be freed using <a href="#n_api_napi_delete_async_work"><code>napi_delete_async_work</code></a> once the work is no longer 4495 required.</p> 4496 <p><code>async_resource_name</code> should be a null-terminated, UTF-8-encoded string.</p> 4497 <p>The <code>async_resource_name</code> identifier is provided by the user and should be 4498 representative of the type of async work being performed. It is also recommended 4499 to apply namespacing to the identifier, e.g. by including the module name. See 4500 the <a href="async_hooks.html#async_hooks_type"><code>async_hooks</code> documentation</a> for more information.</p> 4501 <h4>napi_delete_async_work<span><a class="mark" href="#n_api_napi_delete_async_work" id="n_api_napi_delete_async_work">#</a></span></h4> 4502 <div class="api_metadata"> 4503 <span>Added in: v8.0.0</span> 4504 <span>N-API version: 1</span> 4505 </div> 4506 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_delete_async_work</span><span class="hljs-params">(napi_env env, 4507 napi_async_work work)</span>;</code></pre> 4508 <ul> 4509 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4510 <li><code>[in] work</code>: The handle returned by the call to <code>napi_create_async_work</code>.</li> 4511 </ul> 4512 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4513 <p>This API frees a previously allocated work object.</p> 4514 <p>This API can be called even if there is a pending JavaScript exception.</p> 4515 <h4>napi_queue_async_work<span><a class="mark" href="#n_api_napi_queue_async_work" id="n_api_napi_queue_async_work">#</a></span></h4> 4516 <div class="api_metadata"> 4517 <span>Added in: v8.0.0</span> 4518 <span>N-API version: 1</span> 4519 </div> 4520 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_queue_async_work</span><span class="hljs-params">(napi_env env, 4521 napi_async_work work)</span>;</code></pre> 4522 <ul> 4523 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4524 <li><code>[in] work</code>: The handle returned by the call to <code>napi_create_async_work</code>.</li> 4525 </ul> 4526 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4527 <p>This API requests that the previously allocated work be scheduled 4528 for execution. Once it returns successfully, this API must not be called again 4529 with the same <code>napi_async_work</code> item or the result will be undefined.</p> 4530 <h4>napi_cancel_async_work<span><a class="mark" href="#n_api_napi_cancel_async_work" id="n_api_napi_cancel_async_work">#</a></span></h4> 4531 <div class="api_metadata"> 4532 <span>Added in: v8.0.0</span> 4533 <span>N-API version: 1</span> 4534 </div> 4535 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_cancel_async_work</span><span class="hljs-params">(napi_env env, 4536 napi_async_work work)</span>;</code></pre> 4537 <ul> 4538 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4539 <li><code>[in] work</code>: The handle returned by the call to <code>napi_create_async_work</code>.</li> 4540 </ul> 4541 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4542 <p>This API cancels queued work if it has not yet 4543 been started. If it has already started executing, it cannot be 4544 cancelled and <code>napi_generic_failure</code> will be returned. If successful, 4545 the <code>complete</code> callback will be invoked with a status value of 4546 <code>napi_cancelled</code>. The work should not be deleted before the <code>complete</code> 4547 callback invocation, even if it has been successfully cancelled.</p> 4548 <p>This API can be called even if there is a pending JavaScript exception.</p> 4549 </section><section><h3>Custom asynchronous operations<span><a class="mark" href="#n_api_custom_asynchronous_operations" id="n_api_custom_asynchronous_operations">#</a></span></h3> 4550 <p>The simple asynchronous work APIs above may not be appropriate for every 4551 scenario. When using any other asynchronous mechanism, the following APIs 4552 are necessary to ensure an asynchronous operation is properly tracked by 4553 the runtime.</p> 4554 <h4>napi_async_init<span><a class="mark" href="#n_api_napi_async_init" id="n_api_napi_async_init">#</a></span></h4> 4555 <div class="api_metadata"> 4556 <span>Added in: v8.6.0</span> 4557 <span>N-API version: 1</span> 4558 </div> 4559 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_async_init</span><span class="hljs-params">(napi_env env, 4560 napi_value async_resource, 4561 napi_value async_resource_name, 4562 napi_async_context* result)</span></code></pre> 4563 <ul> 4564 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4565 <li><code>[in] async_resource</code>: Object associated with the async work 4566 that will be passed to possible <code>async_hooks</code> <a href="async_hooks.html#async_hooks_init_asyncid_type_triggerasyncid_resource"><code>init</code> hooks</a> and can be 4567 accessed by <a href="async_hooks.html#async_hooks_async_hooks_executionasyncresource"><code>async_hooks.executionAsyncResource()</code></a>.</li> 4568 <li><code>[in] async_resource_name</code>: Identifier for the kind of resource that is being 4569 provided for diagnostic information exposed by the <code>async_hooks</code> API.</li> 4570 <li><code>[out] result</code>: The initialized async context.</li> 4571 </ul> 4572 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4573 <p>The <code>async_resource</code> object needs to be kept alive until 4574 <a href="#n_api_napi_async_destroy"><code>napi_async_destroy</code></a> to keep <code>async_hooks</code> related API acts correctly. In 4575 order to retain ABI compatibility with previous versions, <code>napi_async_context</code>s 4576 are not maintaining the strong reference to the <code>async_resource</code> objects to 4577 avoid introducing causing memory leaks. However, if the <code>async_resource</code> is 4578 garbage collected by JavaScript engine before the <code>napi_async_context</code> was 4579 destroyed by <code>napi_async_destroy</code>, calling <code>napi_async_context</code> related APIs 4580 like <a href="#n_api_napi_open_callback_scope"><code>napi_open_callback_scope</code></a> and <a href="#n_api_napi_make_callback"><code>napi_make_callback</code></a> can cause 4581 problems like loss of async context when using the <code>AsyncLocalStoage</code> API.</p> 4582 <p>In order to retain ABI compatibility with previous versions, passing <code>NULL</code> 4583 for <code>async_resource</code> does not result in an error. However, this is not 4584 recommended as this will result poor results with <code>async_hooks</code> 4585 <a href="async_hooks.html#async_hooks_init_asyncid_type_triggerasyncid_resource"><code>init</code> hooks</a> and <code>async_hooks.executionAsyncResource()</code> as the resource is 4586 now required by the underlying <code>async_hooks</code> implementation in order to provide 4587 the linkage between async callbacks.</p> 4588 <h4>napi_async_destroy<span><a class="mark" href="#n_api_napi_async_destroy" id="n_api_napi_async_destroy">#</a></span></h4> 4589 <div class="api_metadata"> 4590 <span>Added in: v8.6.0</span> 4591 <span>N-API version: 1</span> 4592 </div> 4593 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_async_destroy</span><span class="hljs-params">(napi_env env, 4594 napi_async_context async_context)</span>;</code></pre> 4595 <ul> 4596 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4597 <li><code>[in] async_context</code>: The async context to be destroyed.</li> 4598 </ul> 4599 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4600 <p>This API can be called even if there is a pending JavaScript exception.</p> 4601 <h4>napi_make_callback<span><a class="mark" href="#n_api_napi_make_callback" id="n_api_napi_make_callback">#</a></span></h4> 4602 <div class="api_metadata"> 4603 <details class="changelog"><summary>History</summary> 4604 <table> 4605 <tbody><tr><th>Version</th><th>Changes</th></tr> 4606 <tr><td>v8.6.0</td> 4607 <td><p>Added <code>async_context</code> parameter.</p></td></tr> 4608 <tr><td>v8.0.0</td> 4609 <td><p><span>Added in: v8.0.0</span></p></td></tr> 4610 </tbody></table> 4611 </details> 4612 <span>N-API version: 1</span> 4613 </div> 4614 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_make_callback</span><span class="hljs-params">(napi_env env, 4615 napi_async_context async_context, 4616 napi_value recv, 4617 napi_value func, 4618 <span class="hljs-type">size_t</span> argc, 4619 <span class="hljs-keyword">const</span> napi_value* argv, 4620 napi_value* result)</span>;</code></pre> 4621 <ul> 4622 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4623 <li><code>[in] async_context</code>: Context for the async operation that is 4624 invoking the callback. This should normally be a value previously 4625 obtained from <a href="#n_api_napi_async_init"><code>napi_async_init</code></a>. 4626 In order to retain ABI compatibility with previous versions, passing <code>NULL</code> 4627 for <code>async_context</code> does not result in an error. However, this results 4628 in incorrect operation of async hooks. Potential issues include loss of 4629 async context when using the <code>AsyncLocalStorage</code> API.</li> 4630 <li><code>[in] recv</code>: The <code>this</code> value passed to the called function.</li> 4631 <li><code>[in] func</code>: <code>napi_value</code> representing the JavaScript function to be invoked.</li> 4632 <li><code>[in] argc</code>: The count of elements in the <code>argv</code> array.</li> 4633 <li><code>[in] argv</code>: Array of JavaScript values as <code>napi_value</code> representing the 4634 arguments to the function.</li> 4635 <li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript object returned.</li> 4636 </ul> 4637 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4638 <p>This method allows a JavaScript function object to be called from a native 4639 add-on. This API is similar to <code>napi_call_function</code>. However, it is used to call 4640 <em>from</em> native code back <em>into</em> JavaScript <em>after</em> returning from an async 4641 operation (when there is no other script on the stack). It is a fairly simple 4642 wrapper around <code>node::MakeCallback</code>.</p> 4643 <p>Note it is <em>not</em> necessary to use <code>napi_make_callback</code> from within a 4644 <code>napi_async_complete_callback</code>; in that situation the callback's async 4645 context has already been set up, so a direct call to <code>napi_call_function</code> 4646 is sufficient and appropriate. Use of the <code>napi_make_callback</code> function 4647 may be required when implementing custom async behavior that does not use 4648 <code>napi_create_async_work</code>.</p> 4649 <p>Any <code>process.nextTick</code>s or Promises scheduled on the microtask queue by 4650 JavaScript during the callback are ran before returning back to C/C++.</p> 4651 <h4>napi_open_callback_scope<span><a class="mark" href="#n_api_napi_open_callback_scope" id="n_api_napi_open_callback_scope">#</a></span></h4> 4652 <div class="api_metadata"> 4653 <span>Added in: v9.6.0</span> 4654 <span>N-API version: 3</span> 4655 </div> 4656 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_open_callback_scope</span><span class="hljs-params">(napi_env env, 4657 napi_value resource_object, 4658 napi_async_context context, 4659 napi_callback_scope* result)</span></code></pre> 4660 <ul> 4661 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4662 <li><code>[in] resource_object</code>: An object associated with the async work 4663 that will be passed to possible <code>async_hooks</code> <a href="async_hooks.html#async_hooks_init_asyncid_type_triggerasyncid_resource"><code>init</code> hooks</a>. This 4664 parameter has been deprecated and is ignored at runtime. Use the 4665 <code>async_resource</code> parameter in <a href="#n_api_napi_async_init"><code>napi_async_init</code></a> instead.</li> 4666 <li><code>[in] context</code>: Context for the async operation that is invoking the callback. 4667 This should be a value previously obtained from <a href="#n_api_napi_async_init"><code>napi_async_init</code></a>.</li> 4668 <li><code>[out] result</code>: The newly created scope.</li> 4669 </ul> 4670 <p>There are cases (for example, resolving promises) where it is 4671 necessary to have the equivalent of the scope associated with a callback 4672 in place when making certain Node-API calls. If there is no other script on 4673 the stack the <a href="#n_api_napi_open_callback_scope"><code>napi_open_callback_scope</code></a> and 4674 <a href="#n_api_napi_close_callback_scope"><code>napi_close_callback_scope</code></a> functions can be used to open/close 4675 the required scope.</p> 4676 <h4>napi_close_callback_scope<span><a class="mark" href="#n_api_napi_close_callback_scope" id="n_api_napi_close_callback_scope">#</a></span></h4> 4677 <div class="api_metadata"> 4678 <span>Added in: v9.6.0</span> 4679 <span>N-API version: 3</span> 4680 </div> 4681 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_close_callback_scope</span><span class="hljs-params">(napi_env env, 4682 napi_callback_scope scope)</span></code></pre> 4683 <ul> 4684 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4685 <li><code>[in] scope</code>: The scope to be closed.</li> 4686 </ul> 4687 <p>This API can be called even if there is a pending JavaScript exception.</p> 4688 </section><section><h3>Version management<span><a class="mark" href="#n_api_version_management" id="n_api_version_management">#</a></span></h3> 4689 <h4>napi_get_node_version<span><a class="mark" href="#n_api_napi_get_node_version" id="n_api_napi_get_node_version">#</a></span></h4> 4690 <div class="api_metadata"> 4691 <span>Added in: v8.4.0</span> 4692 <span>N-API version: 1</span> 4693 </div> 4694 <pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 4695 <span class="hljs-type">uint32_t</span> major; 4696 <span class="hljs-type">uint32_t</span> minor; 4697 <span class="hljs-type">uint32_t</span> patch; 4698 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* release; 4699 } napi_node_version; 4700 4701 napi_status <span class="hljs-title function_">napi_get_node_version</span><span class="hljs-params">(napi_env env, 4702 <span class="hljs-keyword">const</span> napi_node_version** version)</span>;</code></pre> 4703 <ul> 4704 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4705 <li><code>[out] version</code>: A pointer to version information for Node.js itself.</li> 4706 </ul> 4707 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4708 <p>This function fills the <code>version</code> struct with the major, minor, and patch 4709 version of Node.js that is currently running, and the <code>release</code> field with the 4710 value of <a href="process.html#process_process_release"><code>process.release.name</code></a>.</p> 4711 <p>The returned buffer is statically allocated and does not need to be freed.</p> 4712 <h4>napi_get_version<span><a class="mark" href="#n_api_napi_get_version" id="n_api_napi_get_version">#</a></span></h4> 4713 <div class="api_metadata"> 4714 <span>Added in: v8.0.0</span> 4715 <span>N-API version: 1</span> 4716 </div> 4717 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_version</span><span class="hljs-params">(napi_env env, 4718 <span class="hljs-type">uint32_t</span>* result)</span>;</code></pre> 4719 <ul> 4720 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4721 <li><code>[out] result</code>: The highest version of Node-API supported.</li> 4722 </ul> 4723 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4724 <p>This API returns the highest Node-API version supported by the 4725 Node.js runtime. Node-API is planned to be additive such that 4726 newer releases of Node.js may support additional API functions. 4727 In order to allow an addon to use a newer function when running with 4728 versions of Node.js that support it, while providing 4729 fallback behavior when running with Node.js versions that don't 4730 support it:</p> 4731 <ul> 4732 <li>Call <code>napi_get_version()</code> to determine if the API is available.</li> 4733 <li>If available, dynamically load a pointer to the function using <code>uv_dlsym()</code>.</li> 4734 <li>Use the dynamically loaded pointer to invoke the function.</li> 4735 <li>If the function is not available, provide an alternate implementation 4736 that does not use the function.</li> 4737 </ul> 4738 </section><section><h3>Memory management<span><a class="mark" href="#n_api_memory_management" id="n_api_memory_management">#</a></span></h3> 4739 <h4>napi_adjust_external_memory<span><a class="mark" href="#n_api_napi_adjust_external_memory" id="n_api_napi_adjust_external_memory">#</a></span></h4> 4740 <div class="api_metadata"> 4741 <span>Added in: v8.5.0</span> 4742 <span>N-API version: 1</span> 4743 </div> 4744 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_adjust_external_memory</span><span class="hljs-params">(napi_env env, 4745 <span class="hljs-type">int64_t</span> change_in_bytes, 4746 <span class="hljs-type">int64_t</span>* result)</span>;</code></pre> 4747 <ul> 4748 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4749 <li><code>[in] change_in_bytes</code>: The change in externally allocated memory that is kept 4750 alive by JavaScript objects.</li> 4751 <li><code>[out] result</code>: The adjusted value</li> 4752 </ul> 4753 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4754 <p>This function gives V8 an indication of the amount of externally allocated 4755 memory that is kept alive by JavaScript objects (i.e. a JavaScript object 4756 that points to its own memory allocated by a native module). Registering 4757 externally allocated memory will trigger global garbage collections more 4758 often than it would otherwise.</p> 4759 </section><section><h3>Promises<span><a class="mark" href="#n_api_promises" id="n_api_promises">#</a></span></h3> 4760 <p>Node-API provides facilities for creating <code>Promise</code> objects as described in 4761 <a href="https://tc39.github.io/ecma262/#sec-promise-objects">Section 25.4</a> of the ECMA specification. It implements promises as a pair of 4762 objects. When a promise is created by <code>napi_create_promise()</code>, a "deferred" 4763 object is created and returned alongside the <code>Promise</code>. The deferred object is 4764 bound to the created <code>Promise</code> and is the only means to resolve or reject the 4765 <code>Promise</code> using <code>napi_resolve_deferred()</code> or <code>napi_reject_deferred()</code>. The 4766 deferred object that is created by <code>napi_create_promise()</code> is freed by 4767 <code>napi_resolve_deferred()</code> or <code>napi_reject_deferred()</code>. The <code>Promise</code> object may 4768 be returned to JavaScript where it can be used in the usual fashion.</p> 4769 <p>For example, to create a promise and pass it to an asynchronous worker:</p> 4770 <pre><code class="language-c">napi_deferred deferred; 4771 napi_value promise; 4772 napi_status status; 4773 4774 <span class="hljs-comment">// Create the promise.</span> 4775 status = napi_create_promise(env, &deferred, &promise); 4776 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4777 4778 <span class="hljs-comment">// Pass the deferred to a function that performs an asynchronous action.</span> 4779 do_something_asynchronous(deferred); 4780 4781 <span class="hljs-comment">// Return the promise to JS</span> 4782 <span class="hljs-keyword">return</span> promise;</code></pre> 4783 <p>The above function <code>do_something_asynchronous()</code> would perform its asynchronous 4784 action and then it would resolve or reject the deferred, thereby concluding the 4785 promise and freeing the deferred:</p> 4786 <pre><code class="language-c">napi_deferred deferred; 4787 napi_value undefined; 4788 napi_status status; 4789 4790 <span class="hljs-comment">// Create a value with which to conclude the deferred.</span> 4791 status = napi_get_undefined(env, &undefined); 4792 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4793 4794 <span class="hljs-comment">// Resolve or reject the promise associated with the deferred depending on</span> 4795 <span class="hljs-comment">// whether the asynchronous action succeeded.</span> 4796 <span class="hljs-keyword">if</span> (asynchronous_action_succeeded) { 4797 status = napi_resolve_deferred(env, deferred, undefined); 4798 } <span class="hljs-keyword">else</span> { 4799 status = napi_reject_deferred(env, deferred, undefined); 4800 } 4801 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4802 4803 <span class="hljs-comment">// At this point the deferred has been freed, so we should assign NULL to it.</span> 4804 deferred = <span class="hljs-literal">NULL</span>;</code></pre> 4805 <h4>napi_create_promise<span><a class="mark" href="#n_api_napi_create_promise" id="n_api_napi_create_promise">#</a></span></h4> 4806 <div class="api_metadata"> 4807 <span>Added in: v8.5.0</span> 4808 <span>N-API version: 1</span> 4809 </div> 4810 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_promise</span><span class="hljs-params">(napi_env env, 4811 napi_deferred* deferred, 4812 napi_value* promise)</span>;</code></pre> 4813 <ul> 4814 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4815 <li><code>[out] deferred</code>: A newly created deferred object which can later be passed to 4816 <code>napi_resolve_deferred()</code> or <code>napi_reject_deferred()</code> to resolve resp. reject 4817 the associated promise.</li> 4818 <li><code>[out] promise</code>: The JavaScript promise associated with the deferred object.</li> 4819 </ul> 4820 <p>Returns <code>napi_ok</code> if the API succeeded.</p> 4821 <p>This API creates a deferred object and a JavaScript promise.</p> 4822 <h4>napi_resolve_deferred<span><a class="mark" href="#n_api_napi_resolve_deferred" id="n_api_napi_resolve_deferred">#</a></span></h4> 4823 <div class="api_metadata"> 4824 <span>Added in: v8.5.0</span> 4825 <span>N-API version: 1</span> 4826 </div> 4827 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_resolve_deferred</span><span class="hljs-params">(napi_env env, 4828 napi_deferred deferred, 4829 napi_value resolution)</span>;</code></pre> 4830 <ul> 4831 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4832 <li><code>[in] deferred</code>: The deferred object whose associated promise to resolve.</li> 4833 <li><code>[in] resolution</code>: The value with which to resolve the promise.</li> 4834 </ul> 4835 <p>This API resolves a JavaScript promise by way of the deferred object 4836 with which it is associated. Thus, it can only be used to resolve JavaScript 4837 promises for which the corresponding deferred object is available. This 4838 effectively means that the promise must have been created using 4839 <code>napi_create_promise()</code> and the deferred object returned from that call must 4840 have been retained in order to be passed to this API.</p> 4841 <p>The deferred object is freed upon successful completion.</p> 4842 <h4>napi_reject_deferred<span><a class="mark" href="#n_api_napi_reject_deferred" id="n_api_napi_reject_deferred">#</a></span></h4> 4843 <div class="api_metadata"> 4844 <span>Added in: v8.5.0</span> 4845 <span>N-API version: 1</span> 4846 </div> 4847 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_reject_deferred</span><span class="hljs-params">(napi_env env, 4848 napi_deferred deferred, 4849 napi_value rejection)</span>;</code></pre> 4850 <ul> 4851 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4852 <li><code>[in] deferred</code>: The deferred object whose associated promise to resolve.</li> 4853 <li><code>[in] rejection</code>: The value with which to reject the promise.</li> 4854 </ul> 4855 <p>This API rejects a JavaScript promise by way of the deferred object 4856 with which it is associated. Thus, it can only be used to reject JavaScript 4857 promises for which the corresponding deferred object is available. This 4858 effectively means that the promise must have been created using 4859 <code>napi_create_promise()</code> and the deferred object returned from that call must 4860 have been retained in order to be passed to this API.</p> 4861 <p>The deferred object is freed upon successful completion.</p> 4862 <h4>napi_is_promise<span><a class="mark" href="#n_api_napi_is_promise" id="n_api_napi_is_promise">#</a></span></h4> 4863 <div class="api_metadata"> 4864 <span>Added in: v8.5.0</span> 4865 <span>N-API version: 1</span> 4866 </div> 4867 <pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_promise</span><span class="hljs-params">(napi_env env, 4868 napi_value value, 4869 <span class="hljs-type">bool</span>* is_promise)</span>;</code></pre> 4870 <ul> 4871 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4872 <li><code>[in] value</code>: The value to examine</li> 4873 <li><code>[out] is_promise</code>: Flag indicating whether <code>promise</code> is a native promise 4874 object (that is, a promise object created by the underlying engine).</li> 4875 </ul> 4876 </section><section><h3>Script execution<span><a class="mark" href="#n_api_script_execution" id="n_api_script_execution">#</a></span></h3> 4877 <p>Node-API provides an API for executing a string containing JavaScript using the 4878 underlying JavaScript engine.</p> 4879 <h4>napi_run_script<span><a class="mark" href="#n_api_napi_run_script" id="n_api_napi_run_script">#</a></span></h4> 4880 <div class="api_metadata"> 4881 <span>Added in: v8.5.0</span> 4882 <span>N-API version: 1</span> 4883 </div> 4884 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_run_script</span><span class="hljs-params">(napi_env env, 4885 napi_value script, 4886 napi_value* result)</span>;</code></pre> 4887 <ul> 4888 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4889 <li><code>[in] script</code>: A JavaScript string containing the script to execute.</li> 4890 <li><code>[out] result</code>: The value resulting from having executed the script.</li> 4891 </ul> 4892 <p>This function executes a string of JavaScript code and returns its result with 4893 the following caveats:</p> 4894 <ul> 4895 <li>Unlike <code>eval</code>, this function does not allow the script to access the current 4896 lexical scope, and therefore also does not allow to access the 4897 <a href="modules.html#modules_the_module_scope">module scope</a>, meaning that pseudo-globals such as <code>require</code> will not be 4898 available.</li> 4899 <li>The script can access the <a href="globals.html">global scope</a>. Function and <code>var</code> declarations 4900 in the script will be added to the <a href="globals.html#globals_global"><code>global</code></a> object. Variable declarations 4901 made using <code>let</code> and <code>const</code> will be visible globally, but will not be added 4902 to the <a href="globals.html#globals_global"><code>global</code></a> object.</li> 4903 <li>The value of <code>this</code> is <a href="globals.html#globals_global"><code>global</code></a> within the script.</li> 4904 </ul> 4905 </section><section><h3>libuv event loop<span><a class="mark" href="#n_api_libuv_event_loop" id="n_api_libuv_event_loop">#</a></span></h3> 4906 <p>Node-API provides a function for getting the current event loop associated with 4907 a specific <code>napi_env</code>.</p> 4908 <h4>napi_get_uv_event_loop<span><a class="mark" href="#n_api_napi_get_uv_event_loop" id="n_api_napi_get_uv_event_loop">#</a></span></h4> 4909 <div class="api_metadata"> 4910 <span>Added in: v9.3.0, v8.10.0</span> 4911 <span>N-API version: 2</span> 4912 </div> 4913 <pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_get_uv_event_loop</span><span class="hljs-params">(napi_env env, 4914 <span class="hljs-keyword">struct</span> uv_loop_s** loop)</span>;</code></pre> 4915 <ul> 4916 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 4917 <li><code>[out] loop</code>: The current libuv loop instance.</li> 4918 </ul> 4919 </section><section><h3>Asynchronous thread-safe function calls<span><a class="mark" href="#n_api_asynchronous_thread_safe_function_calls" id="n_api_asynchronous_thread_safe_function_calls">#</a></span></h3> 4920 <p>JavaScript functions can normally only be called from a native addon's main 4921 thread. If an addon creates additional threads, then Node-API functions that 4922 require a <code>napi_env</code>, <code>napi_value</code>, or <code>napi_ref</code> must not be called from those 4923 threads.</p> 4924 <p>When an addon has additional threads and JavaScript functions need to be invoked 4925 based on the processing completed by those threads, those threads must 4926 communicate with the addon's main thread so that the main thread can invoke the 4927 JavaScript function on their behalf. The thread-safe function APIs provide an 4928 easy way to do this.</p> 4929 <p>These APIs provide the type <code>napi_threadsafe_function</code> as well as APIs to 4930 create, destroy, and call objects of this type. 4931 <code>napi_create_threadsafe_function()</code> creates a persistent reference to a 4932 <code>napi_value</code> that holds a JavaScript function which can be called from multiple 4933 threads. The calls happen asynchronously. This means that values with which the 4934 JavaScript callback is to be called will be placed in a queue, and, for each 4935 value in the queue, a call will eventually be made to the JavaScript function.</p> 4936 <p>Upon creation of a <code>napi_threadsafe_function</code> a <code>napi_finalize</code> callback can be 4937 provided. This callback will be invoked on the main thread when the thread-safe 4938 function is about to be destroyed. It receives the context and the finalize data 4939 given during construction, and provides an opportunity for cleaning up after the 4940 threads e.g. by calling <code>uv_thread_join()</code>. <strong>Aside from the main loop thread, 4941 no threads should be using the thread-safe function after the finalize callback 4942 completes.</strong></p> 4943 <p>The <code>context</code> given during the call to <code>napi_create_threadsafe_function()</code> can 4944 be retrieved from any thread with a call to 4945 <code>napi_get_threadsafe_function_context()</code>.</p> 4946 <h4>Calling a thread-safe function<span><a class="mark" href="#n_api_calling_a_thread_safe_function" id="n_api_calling_a_thread_safe_function">#</a></span></h4> 4947 <p><code>napi_call_threadsafe_function()</code> can be used for initiating a call into 4948 JavaScript. <code>napi_call_threadsafe_function()</code> accepts a parameter which controls 4949 whether the API behaves blockingly. If set to <code>napi_tsfn_nonblocking</code>, the API 4950 behaves non-blockingly, returning <code>napi_queue_full</code> if the queue was full, 4951 preventing data from being successfully added to the queue. If set to 4952 <code>napi_tsfn_blocking</code>, the API blocks until space becomes available in the queue. 4953 <code>napi_call_threadsafe_function()</code> never blocks if the thread-safe function was 4954 created with a maximum queue size of 0.</p> 4955 <p><code>napi_call_threadsafe_function()</code> should not be called with <code>napi_tsfn_blocking</code> 4956 from a JavaScript thread, because, if the queue is full, it may cause the 4957 JavaScript thread to deadlock.</p> 4958 <p>The actual call into JavaScript is controlled by the callback given via the 4959 <code>call_js_cb</code> parameter. <code>call_js_cb</code> is invoked on the main thread once for each 4960 value that was placed into the queue by a successful call to 4961 <code>napi_call_threadsafe_function()</code>. If such a callback is not given, a default 4962 callback will be used, and the resulting JavaScript call will have no arguments. 4963 The <code>call_js_cb</code> callback receives the JavaScript function to call as a 4964 <code>napi_value</code> in its parameters, as well as the <code>void*</code> context pointer used when 4965 creating the <code>napi_threadsafe_function</code>, and the next data pointer that was 4966 created by one of the secondary threads. The callback can then use an API such 4967 as <code>napi_call_function()</code> to call into JavaScript.</p> 4968 <p>The callback may also be invoked with <code>env</code> and <code>call_js_cb</code> both set to <code>NULL</code> 4969 to indicate that calls into JavaScript are no longer possible, while items 4970 remain in the queue that may need to be freed. This normally occurs when the 4971 Node.js process exits while there is a thread-safe function still active.</p> 4972 <p>It is not necessary to call into JavaScript via <code>napi_make_callback()</code> because 4973 Node-API runs <code>call_js_cb</code> in a context appropriate for callbacks.</p> 4974 <h4>Reference counting of thread-safe functions<span><a class="mark" href="#n_api_reference_counting_of_thread_safe_functions" id="n_api_reference_counting_of_thread_safe_functions">#</a></span></h4> 4975 <p>Threads can be added to and removed from a <code>napi_threadsafe_function</code> object 4976 during its existence. Thus, in addition to specifying an initial number of 4977 threads upon creation, <code>napi_acquire_threadsafe_function</code> can be called to 4978 indicate that a new thread will start making use of the thread-safe function. 4979 Similarly, <code>napi_release_threadsafe_function</code> can be called to indicate that an 4980 existing thread will stop making use of the thread-safe function.</p> 4981 <p><code>napi_threadsafe_function</code> objects are destroyed when every thread which uses 4982 the object has called <code>napi_release_threadsafe_function()</code> or has received a 4983 return status of <code>napi_closing</code> in response to a call to 4984 <code>napi_call_threadsafe_function</code>. The queue is emptied before the 4985 <code>napi_threadsafe_function</code> is destroyed. <code>napi_release_threadsafe_function()</code> 4986 should be the last API call made in conjunction with a given 4987 <code>napi_threadsafe_function</code>, because after the call completes, there is no 4988 guarantee that the <code>napi_threadsafe_function</code> is still allocated. For the same 4989 reason, do not use a thread-safe function 4990 after receiving a return value of <code>napi_closing</code> in response to a call to 4991 <code>napi_call_threadsafe_function</code>. Data associated with the 4992 <code>napi_threadsafe_function</code> can be freed in its <code>napi_finalize</code> callback which 4993 was passed to <code>napi_create_threadsafe_function()</code>. The parameter 4994 <code>initial_thread_count</code> of <code>napi_create_threadsafe_function</code> marks the initial 4995 number of aquisitions of the thread-safe functions, instead of calling 4996 <code>napi_acquire_threadsafe_function</code> multiple times at creation.</p> 4997 <p>Once the number of threads making use of a <code>napi_threadsafe_function</code> reaches 4998 zero, no further threads can start making use of it by calling 4999 <code>napi_acquire_threadsafe_function()</code>. In fact, all subsequent API calls 5000 associated with it, except <code>napi_release_threadsafe_function()</code>, will return an 5001 error value of <code>napi_closing</code>.</p> 5002 <p>The thread-safe function can be "aborted" by giving a value of <code>napi_tsfn_abort</code> 5003 to <code>napi_release_threadsafe_function()</code>. This will cause all subsequent APIs 5004 associated with the thread-safe function except 5005 <code>napi_release_threadsafe_function()</code> to return <code>napi_closing</code> even before its 5006 reference count reaches zero. In particular, <code>napi_call_threadsafe_function()</code> 5007 will return <code>napi_closing</code>, thus informing the threads that it is no longer 5008 possible to make asynchronous calls to the thread-safe function. This can be 5009 used as a criterion for terminating the thread. <strong>Upon receiving a return value 5010 of <code>napi_closing</code> from <code>napi_call_threadsafe_function()</code> a thread must not use 5011 the thread-safe function anymore because it is no longer guaranteed to 5012 be allocated.</strong></p> 5013 <h4>Deciding whether to keep the process running<span><a class="mark" href="#n_api_deciding_whether_to_keep_the_process_running" id="n_api_deciding_whether_to_keep_the_process_running">#</a></span></h4> 5014 <p>Similarly to libuv handles, thread-safe functions can be "referenced" and 5015 "unreferenced". A "referenced" thread-safe function will cause the event loop on 5016 the thread on which it is created to remain alive until the thread-safe function 5017 is destroyed. In contrast, an "unreferenced" thread-safe function will not 5018 prevent the event loop from exiting. The APIs <code>napi_ref_threadsafe_function</code> and 5019 <code>napi_unref_threadsafe_function</code> exist for this purpose.</p> 5020 <p>Neither does <code>napi_unref_threadsafe_function</code> mark the thread-safe functions as 5021 able to be destroyed nor does <code>napi_ref_threadsafe_function</code> prevent it from 5022 being destroyed.</p> 5023 <h4>napi_create_threadsafe_function<span><a class="mark" href="#n_api_napi_create_threadsafe_function" id="n_api_napi_create_threadsafe_function">#</a></span></h4> 5024 <div class="api_metadata"> 5025 <details class="changelog"><summary>History</summary> 5026 <table> 5027 <tbody><tr><th>Version</th><th>Changes</th></tr> 5028 <tr><td>v12.6.0, v10.17.0</td> 5029 <td><p>Made <code>func</code> parameter optional with custom <code>call_js_cb</code>.</p></td></tr> 5030 <tr><td>v10.6.0</td> 5031 <td><p><span>Added in: v10.6.0</span></p></td></tr> 5032 </tbody></table> 5033 </details> 5034 <span>N-API version: 4</span> 5035 </div> 5036 <pre><code class="language-c">NAPI_EXTERN napi_status 5037 <span class="hljs-title function_">napi_create_threadsafe_function</span><span class="hljs-params">(napi_env env, 5038 napi_value func, 5039 napi_value async_resource, 5040 napi_value async_resource_name, 5041 <span class="hljs-type">size_t</span> max_queue_size, 5042 <span class="hljs-type">size_t</span> initial_thread_count, 5043 <span class="hljs-type">void</span>* thread_finalize_data, 5044 napi_finalize thread_finalize_cb, 5045 <span class="hljs-type">void</span>* context, 5046 napi_threadsafe_function_call_js call_js_cb, 5047 napi_threadsafe_function* result)</span>;</code></pre> 5048 <ul> 5049 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 5050 <li><code>[in] func</code>: An optional JavaScript function to call from another thread. It 5051 must be provided if <code>NULL</code> is passed to <code>call_js_cb</code>.</li> 5052 <li><code>[in] async_resource</code>: An optional object associated with the async work that 5053 will be passed to possible <code>async_hooks</code> <a href="async_hooks.html#async_hooks_init_asyncid_type_triggerasyncid_resource"><code>init</code> hooks</a>.</li> 5054 <li><code>[in] async_resource_name</code>: A JavaScript string to provide an identifier for 5055 the kind of resource that is being provided for diagnostic information exposed 5056 by the <code>async_hooks</code> API.</li> 5057 <li><code>[in] max_queue_size</code>: Maximum size of the queue. <code>0</code> for no limit.</li> 5058 <li><code>[in] initial_thread_count</code>: The initial number of acquisitions, i.e. the 5059 initial number of threads, including the main thread, which will be making use 5060 of this function.</li> 5061 <li><code>[in] thread_finalize_data</code>: Optional data to be passed to <code>thread_finalize_cb</code>.</li> 5062 <li><code>[in] thread_finalize_cb</code>: Optional function to call when the 5063 <code>napi_threadsafe_function</code> is being destroyed.</li> 5064 <li><code>[in] context</code>: Optional data to attach to the resulting 5065 <code>napi_threadsafe_function</code>.</li> 5066 <li><code>[in] call_js_cb</code>: Optional callback which calls the JavaScript function in 5067 response to a call on a different thread. This callback will be called on the 5068 main thread. If not given, the JavaScript function will be called with no 5069 parameters and with <code>undefined</code> as its <code>this</code> value. 5070 <a href="#n_api_napi_threadsafe_function_call_js"><code>napi_threadsafe_function_call_js</code></a> provides more details.</li> 5071 <li><code>[out] result</code>: The asynchronous thread-safe JavaScript function.</li> 5072 </ul> 5073 <h4>napi_get_threadsafe_function_context<span><a class="mark" href="#n_api_napi_get_threadsafe_function_context" id="n_api_napi_get_threadsafe_function_context">#</a></span></h4> 5074 <div class="api_metadata"> 5075 <span>Added in: v10.6.0</span> 5076 <span>N-API version: 4</span> 5077 </div> 5078 <pre><code class="language-c">NAPI_EXTERN napi_status 5079 <span class="hljs-title function_">napi_get_threadsafe_function_context</span><span class="hljs-params">(napi_threadsafe_function func, 5080 <span class="hljs-type">void</span>** result)</span>;</code></pre> 5081 <ul> 5082 <li><code>[in] func</code>: The thread-safe function for which to retrieve the context.</li> 5083 <li><code>[out] result</code>: The location where to store the context.</li> 5084 </ul> 5085 <p>This API may be called from any thread which makes use of <code>func</code>.</p> 5086 <h4>napi_call_threadsafe_function<span><a class="mark" href="#n_api_napi_call_threadsafe_function" id="n_api_napi_call_threadsafe_function">#</a></span></h4> 5087 <div class="api_metadata"> 5088 <details class="changelog"><summary>History</summary> 5089 <table> 5090 <tbody><tr><th>Version</th><th>Changes</th></tr> 5091 <tr><td>v14.5.0</td> 5092 <td><p>Support for <code>napi_would_deadlock</code> has been reverted.</p></td></tr> 5093 <tr><td>v14.1.0</td> 5094 <td><p>Return <code>napi_would_deadlock</code> when called with <code>napi_tsfn_blocking</code> from the main thread or a worker thread and the queue is full.</p></td></tr> 5095 <tr><td>v10.6.0</td> 5096 <td><p><span>Added in: v10.6.0</span></p></td></tr> 5097 </tbody></table> 5098 </details> 5099 <span>N-API version: 4</span> 5100 </div> 5101 <pre><code class="language-c">NAPI_EXTERN napi_status 5102 <span class="hljs-title function_">napi_call_threadsafe_function</span><span class="hljs-params">(napi_threadsafe_function func, 5103 <span class="hljs-type">void</span>* data, 5104 napi_threadsafe_function_call_mode is_blocking)</span>;</code></pre> 5105 <ul> 5106 <li><code>[in] func</code>: The asynchronous thread-safe JavaScript function to invoke.</li> 5107 <li><code>[in] data</code>: Data to send into JavaScript via the callback <code>call_js_cb</code> 5108 provided during the creation of the thread-safe JavaScript function.</li> 5109 <li><code>[in] is_blocking</code>: Flag whose value can be either <code>napi_tsfn_blocking</code> to 5110 indicate that the call should block if the queue is full or 5111 <code>napi_tsfn_nonblocking</code> to indicate that the call should return immediately 5112 with a status of <code>napi_queue_full</code> whenever the queue is full.</li> 5113 </ul> 5114 <p>This API should not be called with <code>napi_tsfn_blocking</code> from a JavaScript 5115 thread, because, if the queue is full, it may cause the JavaScript thread to 5116 deadlock.</p> 5117 <p>This API will return <code>napi_closing</code> if <code>napi_release_threadsafe_function()</code> was 5118 called with <code>abort</code> set to <code>napi_tsfn_abort</code> from any thread. The value is only 5119 added to the queue if the API returns <code>napi_ok</code>.</p> 5120 <p>This API may be called from any thread which makes use of <code>func</code>.</p> 5121 <h4>napi_acquire_threadsafe_function<span><a class="mark" href="#n_api_napi_acquire_threadsafe_function" id="n_api_napi_acquire_threadsafe_function">#</a></span></h4> 5122 <div class="api_metadata"> 5123 <span>Added in: v10.6.0</span> 5124 <span>N-API version: 4</span> 5125 </div> 5126 <pre><code class="language-c">NAPI_EXTERN napi_status 5127 <span class="hljs-title function_">napi_acquire_threadsafe_function</span><span class="hljs-params">(napi_threadsafe_function func)</span>;</code></pre> 5128 <ul> 5129 <li><code>[in] func</code>: The asynchronous thread-safe JavaScript function to start making 5130 use of.</li> 5131 </ul> 5132 <p>A thread should call this API before passing <code>func</code> to any other thread-safe 5133 function APIs to indicate that it will be making use of <code>func</code>. This prevents 5134 <code>func</code> from being destroyed when all other threads have stopped making use of 5135 it.</p> 5136 <p>This API may be called from any thread which will start making use of <code>func</code>.</p> 5137 <h4>napi_release_threadsafe_function<span><a class="mark" href="#n_api_napi_release_threadsafe_function" id="n_api_napi_release_threadsafe_function">#</a></span></h4> 5138 <div class="api_metadata"> 5139 <span>Added in: v10.6.0</span> 5140 <span>N-API version: 4</span> 5141 </div> 5142 <pre><code class="language-c">NAPI_EXTERN napi_status 5143 <span class="hljs-title function_">napi_release_threadsafe_function</span><span class="hljs-params">(napi_threadsafe_function func, 5144 napi_threadsafe_function_release_mode mode)</span>;</code></pre> 5145 <ul> 5146 <li><code>[in] func</code>: The asynchronous thread-safe JavaScript function whose reference 5147 count to decrement.</li> 5148 <li><code>[in] mode</code>: Flag whose value can be either <code>napi_tsfn_release</code> to indicate 5149 that the current thread will make no further calls to the thread-safe 5150 function, or <code>napi_tsfn_abort</code> to indicate that in addition to the current 5151 thread, no other thread should make any further calls to the thread-safe 5152 function. If set to <code>napi_tsfn_abort</code>, further calls to 5153 <code>napi_call_threadsafe_function()</code> will return <code>napi_closing</code>, and no further 5154 values will be placed in the queue.</li> 5155 </ul> 5156 <p>A thread should call this API when it stops making use of <code>func</code>. Passing <code>func</code> 5157 to any thread-safe APIs after having called this API has undefined results, as 5158 <code>func</code> may have been destroyed.</p> 5159 <p>This API may be called from any thread which will stop making use of <code>func</code>.</p> 5160 <h4>napi_ref_threadsafe_function<span><a class="mark" href="#n_api_napi_ref_threadsafe_function" id="n_api_napi_ref_threadsafe_function">#</a></span></h4> 5161 <div class="api_metadata"> 5162 <span>Added in: v10.6.0</span> 5163 <span>N-API version: 4</span> 5164 </div> 5165 <pre><code class="language-c">NAPI_EXTERN napi_status 5166 <span class="hljs-title function_">napi_ref_threadsafe_function</span><span class="hljs-params">(napi_env env, napi_threadsafe_function func)</span>;</code></pre> 5167 <ul> 5168 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 5169 <li><code>[in] func</code>: The thread-safe function to reference.</li> 5170 </ul> 5171 <p>This API is used to indicate that the event loop running on the main thread 5172 should not exit until <code>func</code> has been destroyed. Similar to <a href="https://docs.libuv.org/en/v1.x/handle.html#c.uv_ref"><code>uv_ref</code></a> it is 5173 also idempotent.</p> 5174 <p>Neither does <code>napi_unref_threadsafe_function</code> mark the thread-safe functions as 5175 able to be destroyed nor does <code>napi_ref_threadsafe_function</code> prevent it from 5176 being destroyed. <code>napi_acquire_threadsafe_function</code> and 5177 <code>napi_release_threadsafe_function</code> are available for that purpose.</p> 5178 <p>This API may only be called from the main thread.</p> 5179 <h4>napi_unref_threadsafe_function<span><a class="mark" href="#n_api_napi_unref_threadsafe_function" id="n_api_napi_unref_threadsafe_function">#</a></span></h4> 5180 <div class="api_metadata"> 5181 <span>Added in: v10.6.0</span> 5182 <span>N-API version: 4</span> 5183 </div> 5184 <pre><code class="language-c">NAPI_EXTERN napi_status 5185 <span class="hljs-title function_">napi_unref_threadsafe_function</span><span class="hljs-params">(napi_env env, napi_threadsafe_function func)</span>;</code></pre> 5186 <ul> 5187 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 5188 <li><code>[in] func</code>: The thread-safe function to unreference.</li> 5189 </ul> 5190 <p>This API is used to indicate that the event loop running on the main thread 5191 may exit before <code>func</code> is destroyed. Similar to <a href="https://docs.libuv.org/en/v1.x/handle.html#c.uv_unref"><code>uv_unref</code></a> it is also 5192 idempotent.</p> 5193 <p>This API may only be called from the main thread.</p> 5194 </section><section><h3>Miscellaneous utilities<span><a class="mark" href="#n_api_miscellaneous_utilities" id="n_api_miscellaneous_utilities">#</a></span></h3> 5195 </section><section><h3>node_api_get_module_file_name<span><a class="mark" href="#n_api_node_api_get_module_file_name" id="n_api_node_api_get_module_file_name">#</a></span></h3> 5196 <div class="api_metadata"> 5197 <span>Added in: v14.18.0</span> 5198 </div> 5199 <p></p><div class="api_stability api_stability_1"><a href="documentation.html#documentation_stability_index">Stability: 1</a> - Experimental</div><p></p> 5200 <pre><code class="language-c">NAPI_EXTERN napi_status 5201 <span class="hljs-title function_">node_api_get_module_file_name</span><span class="hljs-params">(napi_env env, <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>** result)</span>; 5202 </code></pre> 5203 <ul> 5204 <li><code>[in] env</code>: The environment that the API is invoked under.</li> 5205 <li><code>[out] result</code>: A URL containing the absolute path of the 5206 location from which the add-on was loaded. For a file on the local 5207 file system it will start with <code>file://</code>. The string is null-terminated and 5208 owned by <code>env</code> and must thus not be modified or freed.</li> 5209 </ul> 5210 <p><code>result</code> may be an empty string if the add-on loading process fails to establish 5211 the add-on's file name during loading.</p></section> 5212 <!-- API END --> 5213 </div> 5214 </div> 5215 </div> 5216 <script> 5217 'use strict'; 5218 { 5219 const kCustomPreference = 'customDarkTheme'; 5220 const userSettings = sessionStorage.getItem(kCustomPreference); 5221 const themeToggleButton = document.getElementById('theme-toggle-btn'); 5222 if (userSettings === null && window.matchMedia) { 5223 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 5224 if ('onchange' in mq) { 5225 function mqChangeListener(e) { 5226 document.body.classList.toggle('dark-mode', e.matches); 5227 } 5228 mq.addEventListener('change', mqChangeListener); 5229 if (themeToggleButton) { 5230 themeToggleButton.addEventListener('click', function() { 5231 mq.removeEventListener('change', mqChangeListener); 5232 }, { once: true }); 5233 } 5234 } 5235 if (mq.matches) { 5236 document.body.classList.add('dark-mode'); 5237 } 5238 } else if (userSettings === 'true') { 5239 document.body.classList.add('dark-mode'); 5240 } 5241 if (themeToggleButton) { 5242 themeToggleButton.hidden = false; 5243 themeToggleButton.addEventListener('click', function() { 5244 sessionStorage.setItem( 5245 kCustomPreference, 5246 document.body.classList.toggle('dark-mode') 5247 ); 5248 }); 5249 } 5250 } 5251 </script> 5252 </body> 5253 </html> 5254