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="v14.21.2"> 7 <title>Node-API | Node.js v14.21.2 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" class="nav-deprecations">Deprecated 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<header> 91 <div class="header-container"> 92 <h1>Node.js v14.21.2 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 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 3.91l-1.41-1.41-1.79 1.79 1.41 1.41 1.79-1.79zm-3.21 13.7l1.79 1.8 1.41-1.41-1.8-1.79-1.4 1.4zM20 10.5v2h3v-2h-3zm-8-5c-3.31 0-6 2.69-6 6s2.69 6 6 6 6-2.69 6-6-2.69-6-6-6zm-1 16.95h2V19.5h-2v2.95zm-7.45-3.91l1.41 1.41 1.79-1.8-1.41-1.41-1.79 1.8z"/> 102 </svg> 103 </button> 104 </div> 105 <div id="gtoc"> 106 <ul> 107 <li> 108 <a href="index.html">Index</a> 109 </li> 110 <li> 111 <a href="all.html">View on single page</a> 112 </li> 113 <li> 114 <a href="n-api.json">View as JSON</a> 115 </li> 116 117 <li class="version-picker"> 118 <a href="#">View another version <span>▼</span></a> 119 <ol class="version-picker"><li><a href="https://nodejs.org/docs/latest-v19.x/api/n-api.html">19.x</a></li> 120<li><a href="https://nodejs.org/docs/latest-v18.x/api/n-api.html">18.x <b>LTS</b></a></li> 121<li><a href="https://nodejs.org/docs/latest-v17.x/api/n-api.html">17.x</a></li> 122<li><a href="https://nodejs.org/docs/latest-v16.x/api/n-api.html">16.x <b>LTS</b></a></li> 123<li><a href="https://nodejs.org/docs/latest-v15.x/api/n-api.html">15.x</a></li> 124<li><a href="https://nodejs.org/docs/latest-v14.x/api/n-api.html">14.x <b>LTS</b></a></li> 125<li><a href="https://nodejs.org/docs/latest-v13.x/api/n-api.html">13.x</a></li> 126<li><a href="https://nodejs.org/docs/latest-v12.x/api/n-api.html">12.x</a></li> 127<li><a href="https://nodejs.org/docs/latest-v11.x/api/n-api.html">11.x</a></li> 128<li><a href="https://nodejs.org/docs/latest-v10.x/api/n-api.html">10.x</a></li> 129<li><a href="https://nodejs.org/docs/latest-v9.x/api/n-api.html">9.x</a></li> 130<li><a href="https://nodejs.org/docs/latest-v8.x/api/n-api.html">8.x</a></li></ol> 131 </li> 132 133 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/n-api.md">Edit on GitHub</a></li> 134 </ul> 135 </div> 136 <hr> 137 </header> 138 139 <details id="toc" open><summary>Table of contents</summary><ul> 140<li><span class="stability_2"><a href="#n_api_node_api">Node-API</a></span> 141<ul> 142<li><a href="#n_api_implications_of_abi_stability">Implications of ABI stability</a></li> 143<li><a href="#n_api_building">Building</a> 144<ul> 145<li><a href="#n_api_build_tools">Build tools</a> 146<ul> 147<li><a href="#n_api_node_gyp">node-gyp</a></li> 148<li><a href="#n_api_cmake_js">CMake.js</a></li> 149</ul> 150</li> 151<li><a href="#n_api_uploading_precompiled_binaries">Uploading precompiled binaries</a> 152<ul> 153<li><a href="#n_api_node_pre_gyp">node-pre-gyp</a></li> 154<li><a href="#n_api_prebuild">prebuild</a></li> 155<li><a href="#n_api_prebuildify">prebuildify</a></li> 156</ul> 157</li> 158</ul> 159</li> 160<li><a href="#n_api_usage">Usage</a></li> 161<li><a href="#n_api_node_api_version_matrix">Node-API version matrix</a></li> 162<li><a href="#n_api_environment_life_cycle_apis">Environment life cycle APIs</a> 163<ul> 164<li><a href="#n_api_napi_set_instance_data">napi_set_instance_data</a></li> 165<li><a href="#n_api_napi_get_instance_data">napi_get_instance_data</a></li> 166</ul> 167</li> 168<li><a href="#n_api_basic_node_api_data_types">Basic Node-API data types</a> 169<ul> 170<li><a href="#n_api_napi_status">napi_status</a></li> 171<li><a href="#n_api_napi_extended_error_info">napi_extended_error_info</a></li> 172<li><a href="#n_api_napi_env">napi_env</a></li> 173<li><a href="#n_api_napi_value">napi_value</a></li> 174<li><a href="#n_api_napi_threadsafe_function">napi_threadsafe_function</a></li> 175<li><a href="#n_api_napi_threadsafe_function_release_mode">napi_threadsafe_function_release_mode</a></li> 176<li><a href="#n_api_napi_threadsafe_function_call_mode">napi_threadsafe_function_call_mode</a></li> 177<li><a href="#n_api_node_api_memory_management_types">Node-API memory management types</a> 178<ul> 179<li><a href="#n_api_napi_handle_scope">napi_handle_scope</a></li> 180<li><a href="#n_api_napi_escapable_handle_scope">napi_escapable_handle_scope</a></li> 181<li><a href="#n_api_napi_ref">napi_ref</a></li> 182<li><a href="#n_api_napi_type_tag">napi_type_tag</a></li> 183<li><a href="#n_api_napi_async_cleanup_hook_handle">napi_async_cleanup_hook_handle</a></li> 184</ul> 185</li> 186<li><a href="#n_api_node_api_callback_types">Node-API callback types</a> 187<ul> 188<li><a href="#n_api_napi_callback_info">napi_callback_info</a></li> 189<li><a href="#n_api_napi_callback">napi_callback</a></li> 190<li><a href="#n_api_napi_finalize">napi_finalize</a></li> 191<li><a href="#n_api_napi_async_execute_callback">napi_async_execute_callback</a></li> 192<li><a href="#n_api_napi_async_complete_callback">napi_async_complete_callback</a></li> 193<li><a href="#n_api_napi_threadsafe_function_call_js">napi_threadsafe_function_call_js</a></li> 194<li><a href="#n_api_napi_async_cleanup_hook">napi_async_cleanup_hook</a></li> 195</ul> 196</li> 197</ul> 198</li> 199<li><a href="#n_api_error_handling">Error handling</a> 200<ul> 201<li><a href="#n_api_return_values">Return values</a> 202<ul> 203<li><a href="#n_api_napi_get_last_error_info">napi_get_last_error_info</a></li> 204</ul> 205</li> 206<li><a href="#n_api_exceptions">Exceptions</a> 207<ul> 208<li><a href="#n_api_napi_throw">napi_throw</a></li> 209<li><a href="#n_api_napi_throw_error">napi_throw_error</a></li> 210<li><a href="#n_api_napi_throw_type_error">napi_throw_type_error</a></li> 211<li><a href="#n_api_napi_throw_range_error">napi_throw_range_error</a></li> 212<li><a href="#n_api_napi_is_error">napi_is_error</a></li> 213<li><a href="#n_api_napi_create_error">napi_create_error</a></li> 214<li><a href="#n_api_napi_create_type_error">napi_create_type_error</a></li> 215<li><a href="#n_api_napi_create_range_error">napi_create_range_error</a></li> 216<li><a href="#n_api_napi_get_and_clear_last_exception">napi_get_and_clear_last_exception</a></li> 217<li><a href="#n_api_napi_is_exception_pending">napi_is_exception_pending</a></li> 218<li><a href="#n_api_napi_fatal_exception">napi_fatal_exception</a></li> 219</ul> 220</li> 221<li><a href="#n_api_fatal_errors">Fatal errors</a> 222<ul> 223<li><a href="#n_api_napi_fatal_error">napi_fatal_error</a></li> 224</ul> 225</li> 226</ul> 227</li> 228<li><a href="#n_api_object_lifetime_management">Object lifetime management</a> 229<ul> 230<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> 231<ul> 232<li><a href="#n_api_napi_open_handle_scope">napi_open_handle_scope</a></li> 233<li><a href="#n_api_napi_close_handle_scope">napi_close_handle_scope</a></li> 234<li><a href="#n_api_napi_open_escapable_handle_scope">napi_open_escapable_handle_scope</a></li> 235<li><a href="#n_api_napi_close_escapable_handle_scope">napi_close_escapable_handle_scope</a></li> 236<li><a href="#n_api_napi_escape_handle">napi_escape_handle</a></li> 237</ul> 238</li> 239<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> 240<ul> 241<li><a href="#n_api_napi_create_reference">napi_create_reference</a></li> 242<li><a href="#n_api_napi_delete_reference">napi_delete_reference</a></li> 243<li><a href="#n_api_napi_reference_ref">napi_reference_ref</a></li> 244<li><a href="#n_api_napi_reference_unref">napi_reference_unref</a></li> 245<li><a href="#n_api_napi_get_reference_value">napi_get_reference_value</a></li> 246</ul> 247</li> 248<li><a href="#n_api_cleanup_on_exit_of_the_current_node_js_instance">Cleanup on exit of the current Node.js instance</a> 249<ul> 250<li><a href="#n_api_napi_add_env_cleanup_hook">napi_add_env_cleanup_hook</a></li> 251<li><a href="#n_api_napi_remove_env_cleanup_hook">napi_remove_env_cleanup_hook</a></li> 252<li><a href="#n_api_napi_add_async_cleanup_hook">napi_add_async_cleanup_hook</a></li> 253<li><a href="#n_api_napi_remove_async_cleanup_hook">napi_remove_async_cleanup_hook</a></li> 254</ul> 255</li> 256</ul> 257</li> 258<li><a href="#n_api_module_registration">Module registration</a></li> 259<li><a href="#n_api_working_with_javascript_values">Working with JavaScript values</a> 260<ul> 261<li><a href="#n_api_enum_types">Enum types</a> 262<ul> 263<li><a href="#n_api_napi_key_collection_mode">napi_key_collection_mode</a></li> 264<li><a href="#n_api_napi_key_filter">napi_key_filter</a></li> 265<li><a href="#n_api_napi_key_conversion">napi_key_conversion</a></li> 266<li><a href="#n_api_napi_valuetype">napi_valuetype</a></li> 267<li><a href="#n_api_napi_typedarray_type">napi_typedarray_type</a></li> 268</ul> 269</li> 270<li><a href="#n_api_object_creation_functions">Object creation functions</a> 271<ul> 272<li><a href="#n_api_napi_create_array">napi_create_array</a></li> 273<li><a href="#n_api_napi_create_array_with_length">napi_create_array_with_length</a></li> 274<li><a href="#n_api_napi_create_arraybuffer">napi_create_arraybuffer</a></li> 275<li><a href="#n_api_napi_create_buffer">napi_create_buffer</a></li> 276<li><a href="#n_api_napi_create_buffer_copy">napi_create_buffer_copy</a></li> 277<li><a href="#n_api_napi_create_date">napi_create_date</a></li> 278<li><a href="#n_api_napi_create_external">napi_create_external</a></li> 279<li><a href="#n_api_napi_create_external_arraybuffer">napi_create_external_arraybuffer</a></li> 280<li><a href="#n_api_napi_create_external_buffer">napi_create_external_buffer</a></li> 281<li><a href="#n_api_napi_create_object">napi_create_object</a></li> 282<li><a href="#n_api_napi_create_symbol">napi_create_symbol</a></li> 283<li><a href="#n_api_napi_create_typedarray">napi_create_typedarray</a></li> 284<li><a href="#n_api_napi_create_dataview">napi_create_dataview</a></li> 285</ul> 286</li> 287<li><a href="#n_api_functions_to_convert_from_c_types_to_node_api">Functions to convert from C types to Node-API</a> 288<ul> 289<li><a href="#n_api_napi_create_int32">napi_create_int32</a></li> 290<li><a href="#n_api_napi_create_uint32">napi_create_uint32</a></li> 291<li><a href="#n_api_napi_create_int64">napi_create_int64</a></li> 292<li><a href="#n_api_napi_create_double">napi_create_double</a></li> 293<li><a href="#n_api_napi_create_bigint_int64">napi_create_bigint_int64</a></li> 294<li><a href="#n_api_napi_create_bigint_uint64">napi_create_bigint_uint64</a></li> 295<li><a href="#n_api_napi_create_bigint_words">napi_create_bigint_words</a></li> 296<li><a href="#n_api_napi_create_string_latin1">napi_create_string_latin1</a></li> 297<li><a href="#n_api_napi_create_string_utf16">napi_create_string_utf16</a></li> 298<li><a href="#n_api_napi_create_string_utf8">napi_create_string_utf8</a></li> 299</ul> 300</li> 301<li><a href="#n_api_functions_to_convert_from_node_api_to_c_types">Functions to convert from Node-API to C types</a> 302<ul> 303<li><a href="#n_api_napi_get_array_length">napi_get_array_length</a></li> 304<li><a href="#n_api_napi_get_arraybuffer_info">napi_get_arraybuffer_info</a></li> 305<li><a href="#n_api_napi_get_buffer_info">napi_get_buffer_info</a></li> 306<li><a href="#n_api_napi_get_prototype">napi_get_prototype</a></li> 307<li><a href="#n_api_napi_get_typedarray_info">napi_get_typedarray_info</a></li> 308<li><a href="#n_api_napi_get_dataview_info">napi_get_dataview_info</a></li> 309<li><a href="#n_api_napi_get_date_value">napi_get_date_value</a></li> 310<li><a href="#n_api_napi_get_value_bool">napi_get_value_bool</a></li> 311<li><a href="#n_api_napi_get_value_double">napi_get_value_double</a></li> 312<li><a href="#n_api_napi_get_value_bigint_int64">napi_get_value_bigint_int64</a></li> 313<li><a href="#n_api_napi_get_value_bigint_uint64">napi_get_value_bigint_uint64</a></li> 314<li><a href="#n_api_napi_get_value_bigint_words">napi_get_value_bigint_words</a></li> 315<li><a href="#n_api_napi_get_value_external">napi_get_value_external</a></li> 316<li><a href="#n_api_napi_get_value_int32">napi_get_value_int32</a></li> 317<li><a href="#n_api_napi_get_value_int64">napi_get_value_int64</a></li> 318<li><a href="#n_api_napi_get_value_string_latin1">napi_get_value_string_latin1</a></li> 319<li><a href="#n_api_napi_get_value_string_utf8">napi_get_value_string_utf8</a></li> 320<li><a href="#n_api_napi_get_value_string_utf16">napi_get_value_string_utf16</a></li> 321<li><a href="#n_api_napi_get_value_uint32">napi_get_value_uint32</a></li> 322</ul> 323</li> 324<li><a href="#n_api_functions_to_get_global_instances">Functions to get global instances</a> 325<ul> 326<li><a href="#n_api_napi_get_boolean">napi_get_boolean</a></li> 327<li><a href="#n_api_napi_get_global">napi_get_global</a></li> 328<li><a href="#n_api_napi_get_null">napi_get_null</a></li> 329<li><a href="#n_api_napi_get_undefined">napi_get_undefined</a></li> 330</ul> 331</li> 332</ul> 333</li> 334<li><a href="#n_api_working_with_javascript_values_and_abstract_operations">Working with JavaScript values and abstract operations</a> 335<ul> 336<li><a href="#n_api_napi_coerce_to_bool">napi_coerce_to_bool</a></li> 337<li><a href="#n_api_napi_coerce_to_number">napi_coerce_to_number</a></li> 338<li><a href="#n_api_napi_coerce_to_object">napi_coerce_to_object</a></li> 339<li><a href="#n_api_napi_coerce_to_string">napi_coerce_to_string</a></li> 340<li><a href="#n_api_napi_typeof">napi_typeof</a></li> 341<li><a href="#n_api_napi_instanceof">napi_instanceof</a></li> 342<li><a href="#n_api_napi_is_array">napi_is_array</a></li> 343<li><a href="#n_api_napi_is_arraybuffer">napi_is_arraybuffer</a></li> 344<li><a href="#n_api_napi_is_buffer">napi_is_buffer</a></li> 345<li><a href="#n_api_napi_is_date">napi_is_date</a></li> 346<li><a href="#n_api_napi_is_error_1">napi_is_error</a></li> 347<li><a href="#n_api_napi_is_typedarray">napi_is_typedarray</a></li> 348<li><a href="#n_api_napi_is_dataview">napi_is_dataview</a></li> 349<li><a href="#n_api_napi_strict_equals">napi_strict_equals</a></li> 350<li><a href="#n_api_napi_detach_arraybuffer">napi_detach_arraybuffer</a></li> 351<li><a href="#n_api_napi_is_detached_arraybuffer">napi_is_detached_arraybuffer</a></li> 352</ul> 353</li> 354<li><a href="#n_api_working_with_javascript_properties">Working with JavaScript properties</a> 355<ul> 356<li><a href="#n_api_structures">Structures</a> 357<ul> 358<li><a href="#n_api_napi_property_attributes">napi_property_attributes</a></li> 359<li><a href="#n_api_napi_property_descriptor">napi_property_descriptor</a></li> 360</ul> 361</li> 362<li><a href="#n_api_functions">Functions</a> 363<ul> 364<li><a href="#n_api_napi_get_property_names">napi_get_property_names</a></li> 365<li><a href="#n_api_napi_get_all_property_names">napi_get_all_property_names</a></li> 366<li><a href="#n_api_napi_set_property">napi_set_property</a></li> 367<li><a href="#n_api_napi_get_property">napi_get_property</a></li> 368<li><a href="#n_api_napi_has_property">napi_has_property</a></li> 369<li><a href="#n_api_napi_delete_property">napi_delete_property</a></li> 370<li><a href="#n_api_napi_has_own_property">napi_has_own_property</a></li> 371<li><a href="#n_api_napi_set_named_property">napi_set_named_property</a></li> 372<li><a href="#n_api_napi_get_named_property">napi_get_named_property</a></li> 373<li><a href="#n_api_napi_has_named_property">napi_has_named_property</a></li> 374<li><a href="#n_api_napi_set_element">napi_set_element</a></li> 375<li><a href="#n_api_napi_get_element">napi_get_element</a></li> 376<li><a href="#n_api_napi_has_element">napi_has_element</a></li> 377<li><a href="#n_api_napi_delete_element">napi_delete_element</a></li> 378<li><a href="#n_api_napi_define_properties">napi_define_properties</a></li> 379<li><a href="#n_api_napi_object_freeze">napi_object_freeze</a></li> 380<li><a href="#n_api_napi_object_seal">napi_object_seal</a></li> 381</ul> 382</li> 383</ul> 384</li> 385<li><a href="#n_api_working_with_javascript_functions">Working with JavaScript functions</a> 386<ul> 387<li><a href="#n_api_napi_call_function">napi_call_function</a></li> 388<li><a href="#n_api_napi_create_function">napi_create_function</a></li> 389<li><a href="#n_api_napi_get_cb_info">napi_get_cb_info</a></li> 390<li><a href="#n_api_napi_get_new_target">napi_get_new_target</a></li> 391<li><a href="#n_api_napi_new_instance">napi_new_instance</a></li> 392</ul> 393</li> 394<li><a href="#n_api_object_wrap">Object wrap</a> 395<ul> 396<li><a href="#n_api_napi_define_class">napi_define_class</a></li> 397<li><a href="#n_api_napi_wrap">napi_wrap</a></li> 398<li><a href="#n_api_napi_unwrap">napi_unwrap</a></li> 399<li><a href="#n_api_napi_remove_wrap">napi_remove_wrap</a></li> 400<li><a href="#n_api_napi_type_tag_object">napi_type_tag_object</a></li> 401<li><a href="#n_api_napi_check_object_type_tag">napi_check_object_type_tag</a></li> 402<li><a href="#n_api_napi_add_finalizer">napi_add_finalizer</a></li> 403</ul> 404</li> 405<li><a href="#n_api_simple_asynchronous_operations">Simple asynchronous operations</a> 406<ul> 407<li><a href="#n_api_napi_create_async_work">napi_create_async_work</a></li> 408<li><a href="#n_api_napi_delete_async_work">napi_delete_async_work</a></li> 409<li><a href="#n_api_napi_queue_async_work">napi_queue_async_work</a></li> 410<li><a href="#n_api_napi_cancel_async_work">napi_cancel_async_work</a></li> 411</ul> 412</li> 413<li><a href="#n_api_custom_asynchronous_operations">Custom asynchronous operations</a> 414<ul> 415<li><a href="#n_api_napi_async_init">napi_async_init</a></li> 416<li><a href="#n_api_napi_async_destroy">napi_async_destroy</a></li> 417<li><a href="#n_api_napi_make_callback">napi_make_callback</a></li> 418<li><a href="#n_api_napi_open_callback_scope">napi_open_callback_scope</a></li> 419<li><a href="#n_api_napi_close_callback_scope">napi_close_callback_scope</a></li> 420</ul> 421</li> 422<li><a href="#n_api_version_management">Version management</a> 423<ul> 424<li><a href="#n_api_napi_get_node_version">napi_get_node_version</a></li> 425<li><a href="#n_api_napi_get_version">napi_get_version</a></li> 426</ul> 427</li> 428<li><a href="#n_api_memory_management">Memory management</a> 429<ul> 430<li><a href="#n_api_napi_adjust_external_memory">napi_adjust_external_memory</a></li> 431</ul> 432</li> 433<li><a href="#n_api_promises">Promises</a> 434<ul> 435<li><a href="#n_api_napi_create_promise">napi_create_promise</a></li> 436<li><a href="#n_api_napi_resolve_deferred">napi_resolve_deferred</a></li> 437<li><a href="#n_api_napi_reject_deferred">napi_reject_deferred</a></li> 438<li><a href="#n_api_napi_is_promise">napi_is_promise</a></li> 439</ul> 440</li> 441<li><a href="#n_api_script_execution">Script execution</a> 442<ul> 443<li><a href="#n_api_napi_run_script">napi_run_script</a></li> 444</ul> 445</li> 446<li><a href="#n_api_libuv_event_loop">libuv event loop</a> 447<ul> 448<li><a href="#n_api_napi_get_uv_event_loop">napi_get_uv_event_loop</a></li> 449</ul> 450</li> 451<li><a href="#n_api_asynchronous_thread_safe_function_calls">Asynchronous thread-safe function calls</a> 452<ul> 453<li><a href="#n_api_calling_a_thread_safe_function">Calling a thread-safe function</a></li> 454<li><a href="#n_api_reference_counting_of_thread_safe_functions">Reference counting of thread-safe functions</a></li> 455<li><a href="#n_api_deciding_whether_to_keep_the_process_running">Deciding whether to keep the process running</a></li> 456<li><a href="#n_api_napi_create_threadsafe_function">napi_create_threadsafe_function</a></li> 457<li><a href="#n_api_napi_get_threadsafe_function_context">napi_get_threadsafe_function_context</a></li> 458<li><a href="#n_api_napi_call_threadsafe_function">napi_call_threadsafe_function</a></li> 459<li><a href="#n_api_napi_acquire_threadsafe_function">napi_acquire_threadsafe_function</a></li> 460<li><a href="#n_api_napi_release_threadsafe_function">napi_release_threadsafe_function</a></li> 461<li><a href="#n_api_napi_ref_threadsafe_function">napi_ref_threadsafe_function</a></li> 462<li><a href="#n_api_napi_unref_threadsafe_function">napi_unref_threadsafe_function</a></li> 463</ul> 464</li> 465<li><a href="#n_api_miscellaneous_utilities">Miscellaneous utilities</a></li> 466<li><span class="stability_1"><a href="#n_api_node_api_get_module_file_name">node_api_get_module_file_name</a></span></li> 467</ul> 468</li> 469</ul></details> 470 471 <div id="apicontent"> 472 <h2>Node-API<span><a class="mark" href="#n_api_node_api" id="n_api_node_api">#</a></span></h2> 473 474 475<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 476<p>Node-API (formerly N-API) is an API for building native Addons. It is 477independent from the underlying JavaScript runtime (for example, V8) and is 478maintained as part of Node.js itself. This API will be Application Binary 479Interface (ABI) stable across versions of Node.js. It is intended to insulate 480addons from changes in the underlying JavaScript engine and allow modules 481compiled for one major version to run on later major versions of Node.js without 482recompilation. The <a href="https://nodejs.org/en/docs/guides/abi-stability/">ABI Stability</a> guide provides a more in-depth explanation.</p> 483<p>Addons are built/packaged with the same approach/tools outlined in the section 484titled <a href="addons.html">C++ Addons</a>. The only difference is the set of APIs that are used by 485the native code. Instead of using the V8 or <a href="https://github.com/nodejs/nan">Native Abstractions for Node.js</a> 486APIs, the functions available in Node-API are used.</p> 487<p>APIs exposed by Node-API are generally used to create and manipulate 488JavaScript values. Concepts and operations generally map to ideas specified 489in the ECMA-262 Language Specification. The APIs have the following 490properties:</p> 491<ul> 492<li>All Node-API calls return a status code of type <code>napi_status</code>. This 493status indicates whether the API call succeeded or failed.</li> 494<li>The API's return value is passed via an out parameter.</li> 495<li>All JavaScript values are abstracted behind an opaque type named 496<code>napi_value</code>.</li> 497<li>In case of an error status code, additional information can be obtained 498using <code>napi_get_last_error_info</code>. More information can be found in the error 499handling section <a href="#n_api_error_handling">Error handling</a>.</li> 500</ul> 501<p>Node-API is a C API that ensures ABI stability across Node.js versions 502and different compiler levels. A C++ API can be easier to use. 503To support using C++, the project maintains a 504C++ wrapper module called <a href="https://github.com/nodejs/node-addon-api"><code>node-addon-api</code></a>. 505This wrapper provides an inlineable C++ API. Binaries built 506with <code>node-addon-api</code> will depend on the symbols for the Node-API C-based 507functions exported by Node.js. <code>node-addon-api</code> is a more 508efficient way to write code that calls Node-API. Take, for example, the 509following <code>node-addon-api</code> code. The first section shows the 510<code>node-addon-api</code> code and the second section shows what actually gets 511used in the addon.</p> 512<pre><code class="language-cpp">Object obj = Object::<span class="hljs-built_in">New</span>(env); 513obj[<span class="hljs-string">"foo"</span>] = String::<span class="hljs-built_in">New</span>(env, <span class="hljs-string">"bar"</span>);</code></pre> 514<pre><code class="language-cpp">napi_status status; 515napi_value object, string; 516status = <span class="hljs-built_in">napi_create_object</span>(env, &object); 517<span class="hljs-keyword">if</span> (status != napi_ok) { 518 <span class="hljs-built_in">napi_throw_error</span>(env, ...); 519 <span class="hljs-keyword">return</span>; 520} 521 522status = <span class="hljs-built_in">napi_create_string_utf8</span>(env, <span class="hljs-string">"bar"</span>, NAPI_AUTO_LENGTH, &string); 523<span class="hljs-keyword">if</span> (status != napi_ok) { 524 <span class="hljs-built_in">napi_throw_error</span>(env, ...); 525 <span class="hljs-keyword">return</span>; 526} 527 528status = <span class="hljs-built_in">napi_set_named_property</span>(env, object, <span class="hljs-string">"foo"</span>, string); 529<span class="hljs-keyword">if</span> (status != napi_ok) { 530 <span class="hljs-built_in">napi_throw_error</span>(env, ...); 531 <span class="hljs-keyword">return</span>; 532}</code></pre> 533<p>The end result is that the addon only uses the exported C APIs. As a result, 534it still gets the benefits of the ABI stability provided by the C API.</p> 535<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> 536for <code>node-addon-api</code>.</p> 537<p>The <a href="https://nodejs.github.io/node-addon-examples/">Node-API Resource</a> offers 538an excellent orientation and tips for developers just getting started with 539Node-API and <code>node-addon-api</code>.</p> 540<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> 541<p>Although Node-API provides an ABI stability guarantee, other parts of Node.js do 542not, and any external libraries used from the addon may not. In particular, 543none of the following APIs provide an ABI stability guarantee across major 544versions:</p> 545<ul> 546<li> 547<p>the Node.js C++ APIs available via any of</p> 548<pre><code class="language-cpp"><span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node.h></span></span> 549<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_buffer.h></span></span> 550<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_version.h></span></span> 551<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_object_wrap.h></span></span></code></pre> 552</li> 553<li> 554<p>the libuv APIs which are also included with Node.js and available via</p> 555<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> 556</li> 557<li> 558<p>the V8 API available via</p> 559<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> 560</li> 561</ul> 562<p>Thus, for an addon to remain ABI-compatible across Node.js major versions, it 563must use Node-API exclusively by restricting itself to using</p> 564<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> 565<p>and by checking, for all external libraries that it uses, that the external 566library makes ABI stability guarantees similar to Node-API.</p> 567</section><section><h3>Building<span><a class="mark" href="#n_api_building" id="n_api_building">#</a></span></h3> 568<p>Unlike modules written in JavaScript, developing and deploying Node.js 569native addons using Node-API requires an additional set of tools. Besides the 570basic tools required to develop for Node.js, the native addon developer 571requires a toolchain that can compile C and C++ code into a binary. In 572addition, depending upon how the native addon is deployed, the <em>user</em> of 573the native addon will also need to have a C/C++ toolchain installed.</p> 574<p>For Linux developers, the necessary C/C++ toolchain packages are readily 575available. <a href="https://gcc.gnu.org">GCC</a> is widely used in the Node.js community to build and 576test across a variety of platforms. For many developers, the <a href="https://llvm.org">LLVM</a> 577compiler infrastructure is also a good choice.</p> 578<p>For Mac developers, <a href="https://developer.apple.com/xcode/">Xcode</a> offers all the required compiler tools. 579However, it is not necessary to install the entire Xcode IDE. The following 580command installs the necessary toolchain:</p> 581<pre><code class="language-bash">xcode-select --install</code></pre> 582<p>For Windows developers, <a href="https://visualstudio.microsoft.com">Visual Studio</a> offers all the required compiler 583tools. However, it is not necessary to install the entire Visual Studio 584IDE. The following command installs the necessary toolchain:</p> 585<pre><code class="language-bash">npm install --global windows-build-tools</code></pre> 586<p>The sections below describe the additional tools available for developing 587and deploying Node.js native addons.</p> 588<h4>Build tools<span><a class="mark" href="#n_api_build_tools" id="n_api_build_tools">#</a></span></h4> 589<p>Both the tools listed here require that <em>users</em> of the native 590addon have a C/C++ toolchain installed in order to successfully install 591the native addon.</p> 592<h5>node-gyp<span><a class="mark" href="#n_api_node_gyp" id="n_api_node_gyp">#</a></span></h5> 593<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 594Google's <a href="https://gyp.gsrc.io">GYP</a> tool and comes bundled with npm. GYP, and therefore node-gyp, 595requires that Python be installed.</p> 596<p>Historically, node-gyp has been the tool of choice for building native 597addons. It has widespread adoption and documentation. However, some 598developers have run into limitations in node-gyp.</p> 599<h5>CMake.js<span><a class="mark" href="#n_api_cmake_js" id="n_api_cmake_js">#</a></span></h5> 600<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> 601<p>CMake.js is a good choice for projects that already use CMake or for 602developers affected by limitations in node-gyp.</p> 603<h4>Uploading precompiled binaries<span><a class="mark" href="#n_api_uploading_precompiled_binaries" id="n_api_uploading_precompiled_binaries">#</a></span></h4> 604<p>The three tools listed here permit native addon developers and maintainers 605to create and upload binaries to public or private servers. These tools are 606typically integrated with CI/CD build systems like <a href="https://travis-ci.org">Travis CI</a> and 607<a href="https://www.appveyor.com">AppVeyor</a> to build and upload binaries for a variety of platforms and 608architectures. These binaries are then available for download by users who 609do not need to have a C/C++ toolchain installed.</p> 610<h5>node-pre-gyp<span><a class="mark" href="#n_api_node_pre_gyp" id="n_api_node_pre_gyp">#</a></span></h5> 611<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 612upload binaries to a server of the developer's choice. node-pre-gyp has 613particularly good support for uploading binaries to Amazon S3.</p> 614<h5>prebuild<span><a class="mark" href="#n_api_prebuild" id="n_api_prebuild">#</a></span></h5> 615<p><a href="https://github.com/prebuild/prebuild">prebuild</a> is a tool that supports builds using either node-gyp or 616CMake.js. Unlike node-pre-gyp which supports a variety of servers, prebuild 617uploads 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 618GitHub projects using CMake.js.</p> 619<h5>prebuildify<span><a class="mark" href="#n_api_prebuildify" id="n_api_prebuildify">#</a></span></h5> 620<p><a href="https://github.com/prebuild/prebuildify">prebuildify</a> is a tool based on node-gyp. The advantage of prebuildify is 621that the built binaries are bundled with the native module when it's 622uploaded to npm. The binaries are downloaded from npm and are immediately 623available to the module user when the native module is installed.</p> 624</section><section><h3>Usage<span><a class="mark" href="#n_api_usage" id="n_api_usage">#</a></span></h3> 625<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 626is located in the src directory in the node development tree:</p> 627<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> 628<p>This will opt into the default <code>NAPI_VERSION</code> for the given release of Node.js. 629In order to ensure compatibility with specific versions of Node-API, the version 630can be specified explicitly when including the header:</p> 631<pre><code class="language-c"><span class="hljs-meta">#<span class="hljs-keyword">define</span> NAPI_VERSION 3</span> 632<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span></code></pre> 633<p>This restricts the Node-API surface to just the functionality that was available 634in the specified (and earlier) versions.</p> 635<p>Some of the Node-API surface is experimental and requires explicit opt-in:</p> 636<pre><code class="language-c"><span class="hljs-meta">#<span class="hljs-keyword">define</span> NAPI_EXPERIMENTAL</span> 637<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span></code></pre> 638<p>In this case the entire API surface, including any experimental APIs, will be 639available to the module code.</p> 640</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> 641<p>Node-API versions are additive and versioned independently from Node.js. 642Version 4 is an extension to version 3 in that it has all of the APIs 643from version 3 with some additions. This means that it is not necessary 644to recompile for new versions of Node.js which are 645listed as supporting a later version.</p> 646<!-- For accessibility purposes, this table needs row headers. That means we 647 can't do it in markdown. Hence, the raw HTML. --> 648<table> 649 <tbody><tr> 650 <td></td> 651 <th scope="col">1</th> 652 <th scope="col">2</th> 653 <th scope="col">3</th> 654 </tr> 655 <tr> 656 <th scope="row">v6.x</th> 657 <td></td> 658 <td></td> 659 <td>v6.14.2*</td> 660 </tr> 661 <tr> 662 <th scope="row">v8.x</th> 663 <td>v8.6.0**</td> 664 <td>v8.10.0*</td> 665 <td>v8.11.2</td> 666 </tr> 667 <tr> 668 <th scope="row">v9.x</th> 669 <td>v9.0.0*</td> 670 <td>v9.3.0*</td> 671 <td>v9.11.0*</td> 672 </tr> 673 <tr> 674 <th scope="row">≥ v10.x</th> 675 <td>all releases</td> 676 <td>all releases</td> 677 <td>all releases</td> 678 </tr> 679</tbody></table> 680<table> 681 <tbody><tr> 682 <td></td> 683 <th scope="col">4</th> 684 <th scope="col">5</th> 685 <th scope="col">6</th> 686 <th scope="col">7</th> 687 <th scope="col">8</th> 688 </tr> 689 <tr> 690 <th scope="row">v10.x</th> 691 <td>v10.16.0</td> 692 <td>v10.17.0</td> 693 <td>v10.20.0</td> 694 <td>v10.23.0</td> 695 <td></td> 696 </tr> 697 <tr> 698 <th scope="row">v11.x</th> 699 <td>v11.8.0</td> 700 <td></td> 701 <td></td> 702 <td></td> 703 <td></td> 704 </tr> 705 <tr> 706 <th scope="row">v12.x</th> 707 <td>v12.0.0</td> 708 <td>v12.11.0</td> 709 <td>v12.17.0</td> 710 <td>v12.19.0</td> 711 <td>v12.22.0</td> 712 </tr> 713 <tr> 714 <th scope="row">v13.x</th> 715 <td>v13.0.0</td> 716 <td>v13.0.0</td> 717 <td></td> 718 <td></td> 719 <td></td> 720 </tr> 721 <tr> 722 <th scope="row">v14.x</th> 723 <td>v14.0.0</td> 724 <td>v14.0.0</td> 725 <td>v14.0.0</td> 726 <td>v14.12.0</td> 727 <td>v14.17.0</td> 728 </tr> 729 <tr> 730 <th scope="row">v15.x</th> 731 <td>v15.0.0</td> 732 <td>v15.0.0</td> 733 <td>v15.0.0</td> 734 <td>v15.0.0</td> 735 <td>v15.12.0</td> 736 </tr> 737 <tr> 738 <th scope="row">v16.x</th> 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 <td>v16.0.0</td> 744 </tr> 745</tbody></table> 746<p>* Node-API was experimental.</p> 747<p>** Node.js 8.0.0 included Node-API as experimental. It was released as 748Node-API version 1 but continued to evolve until Node.js 8.6.0. The API is 749different in versions prior to Node.js 8.6.0. We recommend Node-API version 3 or 750later.</p> 751<p>Each API documented for Node-API will have a header named <code>added in:</code>, and APIs 752which are stable will have the additional header <code>Node-API version:</code>. 753APIs are directly usable when using a Node.js version which supports 754the Node-API version shown in <code>Node-API version:</code> or higher. 755When using a Node.js version that does not support the 756<code>Node-API version:</code> listed or if there is no <code>Node-API version:</code> listed, 757then the API will only be available if 758<code>#define NAPI_EXPERIMENTAL</code> precedes the inclusion of <code>node_api.h</code> 759or <code>js_native_api.h</code>. If an API appears not to be available on 760a version of Node.js which is later than the one shown in <code>added in:</code> then 761this is most likely the reason for the apparent absence.</p> 762<p>The Node-APIs associated strictly with accessing ECMAScript features from native 763code can be found separately in <code>js_native_api.h</code> and <code>js_native_api_types.h</code>. 764The APIs defined in these headers are included in <code>node_api.h</code> and 765<code>node_api_types.h</code>. The headers are structured in this way in order to allow 766implementations of Node-API outside of Node.js. For those implementations the 767Node.js specific APIs may not be applicable.</p> 768<p>The Node.js-specific parts of an addon can be separated from the code that 769exposes the actual functionality to the JavaScript environment so that the 770latter may be used with multiple implementations of Node-API. In the example 771below, <code>addon.c</code> and <code>addon.h</code> refer only to <code>js_native_api.h</code>. This ensures 772that <code>addon.c</code> can be reused to compile against either the Node.js 773implementation of Node-API or any implementation of Node-API outside of Node.js.</p> 774<p><code>addon_node.c</code> is a separate file that contains the Node.js specific entry point 775to the addon and which instantiates the addon by calling into <code>addon.c</code> when the 776addon is loaded into a Node.js environment.</p> 777<pre><code class="language-c"><span class="hljs-comment">// addon.h</span> 778<span class="hljs-meta">#<span class="hljs-keyword">ifndef</span> _ADDON_H_</span> 779<span class="hljs-meta">#<span class="hljs-keyword">define</span> _ADDON_H_</span> 780<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><js_native_api.h></span></span> 781napi_value <span class="hljs-title function_">create_addon</span><span class="hljs-params">(napi_env env)</span>; 782<span class="hljs-meta">#<span class="hljs-keyword">endif</span> <span class="hljs-comment">// _ADDON_H_</span></span></code></pre> 783<pre><code class="language-c"><span class="hljs-comment">// addon.c</span> 784<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string">"addon.h"</span></span> 785 786<span class="hljs-meta">#<span class="hljs-keyword">define</span> NAPI_CALL(env, call) \ 787 do { \ 788 napi_status status = (call); \ 789 <span class="hljs-keyword">if</span> (status != napi_ok) { \ 790 const napi_extended_error_info* error_info = NULL; \ 791 napi_get_last_error_info((env), &error_info); \ 792 bool is_pending; \ 793 napi_is_exception_pending((env), &is_pending); \ 794 <span class="hljs-keyword">if</span> (!is_pending) { \ 795 const char* message = (error_info->error_message == NULL) \ 796 ? <span class="hljs-string">"empty error message"</span> \ 797 : error_info->error_message; \ 798 napi_throw_error((env), NULL, message); \ 799 return NULL; \ 800 } \ 801 } \ 802 } while(0)</span> 803 804<span class="hljs-keyword">static</span> napi_value 805<span class="hljs-title function_">DoSomethingUseful</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 806 <span class="hljs-comment">// Do something useful.</span> 807 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 808} 809 810napi_value <span class="hljs-title function_">create_addon</span><span class="hljs-params">(napi_env env)</span> { 811 napi_value result; 812 NAPI_CALL(env, napi_create_object(env, &result)); 813 814 napi_value exported_function; 815 NAPI_CALL(env, napi_create_function(env, 816 <span class="hljs-string">"doSomethingUseful"</span>, 817 NAPI_AUTO_LENGTH, 818 DoSomethingUseful, 819 <span class="hljs-literal">NULL</span>, 820 &exported_function)); 821 822 NAPI_CALL(env, napi_set_named_property(env, 823 result, 824 <span class="hljs-string">"doSomethingUseful"</span>, 825 exported_function)); 826 827 <span class="hljs-keyword">return</span> result; 828}</code></pre> 829<pre><code class="language-c"><span class="hljs-comment">// addon_node.c</span> 830<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><node_api.h></span></span> 831<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string">"addon.h"</span></span> 832 833NAPI_MODULE_INIT() { 834 <span class="hljs-comment">// This function body is expected to return a `napi_value`.</span> 835 <span class="hljs-comment">// The variables `napi_env env` and `napi_value exports` may be used within</span> 836 <span class="hljs-comment">// the body, as they are provided by the definition of `NAPI_MODULE_INIT()`.</span> 837 <span class="hljs-keyword">return</span> create_addon(env); 838}</code></pre> 839</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> 840<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 841of an "Agent" as a self-contained environment in which JavaScript code runs. 842Multiple such Agents may be started and terminated either concurrently or in 843sequence by the process.</p> 844<p>A Node.js environment corresponds to an ECMAScript Agent. In the main process, 845an environment is created at startup, and additional environments can be created 846on separate threads to serve as <a href="https://nodejs.org/api/worker_threads.html">worker threads</a>. When Node.js is embedded in 847another application, the main thread of the application may also construct and 848destroy a Node.js environment multiple times during the life cycle of the 849application process such that each Node.js environment created by the 850application may, in turn, during its life cycle create and destroy additional 851environments as worker threads.</p> 852<p>From the perspective of a native addon this means that the bindings it provides 853may be called multiple times, from multiple contexts, and even concurrently from 854multiple threads.</p> 855<p>Native addons may need to allocate global state which they use during 856their entire life cycle such that the state must be unique to each instance of 857the addon.</p> 858<p>To this end, Node-API provides a way to allocate data such that its life cycle 859is tied to the life cycle of the Agent.</p> 860<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> 861<div class="api_metadata"> 862<span>Added in: v12.8.0, v10.20.0</span> 863<span>N-API version: 6</span> 864</div> 865<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_instance_data</span><span class="hljs-params">(napi_env env, 866 <span class="hljs-type">void</span>* data, 867 napi_finalize finalize_cb, 868 <span class="hljs-type">void</span>* finalize_hint)</span>;</code></pre> 869<ul> 870<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 871<li><code>[in] data</code>: The data item to make available to bindings of this instance.</li> 872<li><code>[in] finalize_cb</code>: The function to call when the environment is being torn 873down. The function receives <code>data</code> so that it might free it. 874<a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 875<li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 876collection.</li> 877</ul> 878<p>Returns <code>napi_ok</code> if the API succeeded.</p> 879<p>This API associates <code>data</code> with the currently running Agent. <code>data</code> can later 880be retrieved using <code>napi_get_instance_data()</code>. Any existing data associated with 881the currently running Agent which was set by means of a previous call to 882<code>napi_set_instance_data()</code> will be overwritten. If a <code>finalize_cb</code> was provided 883by the previous call, it will not be called.</p> 884<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> 885<div class="api_metadata"> 886<span>Added in: v12.8.0, v10.20.0</span> 887<span>N-API version: 6</span> 888</div> 889<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_instance_data</span><span class="hljs-params">(napi_env env, 890 <span class="hljs-type">void</span>** data)</span>;</code></pre> 891<ul> 892<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 893<li><code>[out] data</code>: The data item that was previously associated with the currently 894running Agent by a call to <code>napi_set_instance_data()</code>.</li> 895</ul> 896<p>Returns <code>napi_ok</code> if the API succeeded.</p> 897<p>This API retrieves data that was previously associated with the currently 898running Agent via <code>napi_set_instance_data()</code>. If no data is set, the call will 899succeed and <code>data</code> will be set to <code>NULL</code>.</p> 900</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> 901<p>Node-API exposes the following fundamental datatypes as abstractions that are 902consumed by the various APIs. These APIs should be treated as opaque, 903introspectable only with other Node-API calls.</p> 904<h4>napi_status<span><a class="mark" href="#n_api_napi_status" id="n_api_napi_status">#</a></span></h4> 905<div class="api_metadata"> 906<span>Added in: v8.0.0</span> 907<span>N-API version: 1</span> 908</div> 909<p>Integral status code indicating the success or failure of a Node-API call. 910Currently, the following status codes are supported.</p> 911<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 912 napi_ok, 913 napi_invalid_arg, 914 napi_object_expected, 915 napi_string_expected, 916 napi_name_expected, 917 napi_function_expected, 918 napi_number_expected, 919 napi_boolean_expected, 920 napi_array_expected, 921 napi_generic_failure, 922 napi_pending_exception, 923 napi_cancelled, 924 napi_escape_called_twice, 925 napi_handle_scope_mismatch, 926 napi_callback_scope_mismatch, 927 napi_queue_full, 928 napi_closing, 929 napi_bigint_expected, 930 napi_date_expected, 931 napi_arraybuffer_expected, 932 napi_detachable_arraybuffer_expected, 933 napi_would_deadlock, <span class="hljs-comment">/* unused */</span> 934 napi_no_external_buffers_allowed 935} napi_status;</code></pre> 936<p>If additional information is required upon an API returning a failed status, 937it can be obtained by calling <code>napi_get_last_error_info</code>.</p> 938<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> 939<div class="api_metadata"> 940<span>Added in: v8.0.0</span> 941<span>N-API version: 1</span> 942</div> 943<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 944 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* error_message; 945 <span class="hljs-type">void</span>* engine_reserved; 946 <span class="hljs-type">uint32_t</span> engine_error_code; 947 napi_status error_code; 948} napi_extended_error_info;</code></pre> 949<ul> 950<li><code>error_message</code>: UTF8-encoded string containing a VM-neutral description of 951the error.</li> 952<li><code>engine_reserved</code>: Reserved for VM-specific error details. This is currently 953not implemented for any VM.</li> 954<li><code>engine_error_code</code>: VM-specific error code. This is currently 955not implemented for any VM.</li> 956<li><code>error_code</code>: The Node-API status code that originated with the last error.</li> 957</ul> 958<p>See the <a href="#n_api_error_handling">Error handling</a> section for additional information.</p> 959<h4>napi_env<span><a class="mark" href="#n_api_napi_env" id="n_api_napi_env">#</a></span></h4> 960<p><code>napi_env</code> is used to represent a context that the underlying Node-API 961implementation can use to persist VM-specific state. This structure is passed 962to native functions when they're invoked, and it must be passed back when 963making Node-API calls. Specifically, the same <code>napi_env</code> that was passed in when 964the initial native function was called must be passed to any subsequent 965nested Node-API calls. Caching the <code>napi_env</code> for the purpose of general reuse, 966and passing the <code>napi_env</code> between instances of the same addon running on 967different <a href="worker_threads.html#worker_threads_class_worker"><code>Worker</code></a> threads is not allowed. The <code>napi_env</code> becomes invalid 968when an instance of a native addon is unloaded. Notification of this event is 969delivered through the callbacks given to <a href="#n_api_napi_add_env_cleanup_hook"><code>napi_add_env_cleanup_hook</code></a> and 970<a href="#n_api_napi_set_instance_data"><code>napi_set_instance_data</code></a>.</p> 971<h4>napi_value<span><a class="mark" href="#n_api_napi_value" id="n_api_napi_value">#</a></span></h4> 972<p>This is an opaque pointer that is used to represent a JavaScript value.</p> 973<h4>napi_threadsafe_function<span><a class="mark" href="#n_api_napi_threadsafe_function" id="n_api_napi_threadsafe_function">#</a></span></h4> 974<div class="api_metadata"> 975<span>Added in: v10.6.0</span> 976<span>N-API version: 4</span> 977</div> 978<p>This is an opaque pointer that represents a JavaScript function which can be 979called asynchronously from multiple threads via 980<code>napi_call_threadsafe_function()</code>.</p> 981<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> 982<div class="api_metadata"> 983<span>Added in: v10.6.0</span> 984<span>N-API version: 4</span> 985</div> 986<p>A value to be given to <code>napi_release_threadsafe_function()</code> to indicate whether 987the thread-safe function is to be closed immediately (<code>napi_tsfn_abort</code>) or 988merely released (<code>napi_tsfn_release</code>) and thus available for subsequent use via 989<code>napi_acquire_threadsafe_function()</code> and <code>napi_call_threadsafe_function()</code>.</p> 990<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 991 napi_tsfn_release, 992 napi_tsfn_abort 993} napi_threadsafe_function_release_mode;</code></pre> 994<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> 995<div class="api_metadata"> 996<span>Added in: v10.6.0</span> 997<span>N-API version: 4</span> 998</div> 999<p>A value to be given to <code>napi_call_threadsafe_function()</code> to indicate whether 1000the call should block whenever the queue associated with the thread-safe 1001function is full.</p> 1002<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 1003 napi_tsfn_nonblocking, 1004 napi_tsfn_blocking 1005} napi_threadsafe_function_call_mode;</code></pre> 1006<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> 1007<h5>napi_handle_scope<span><a class="mark" href="#n_api_napi_handle_scope" id="n_api_napi_handle_scope">#</a></span></h5> 1008<p>This is an abstraction used to control and modify the lifetime of objects 1009created within a particular scope. In general, Node-API values are created 1010within the context of a handle scope. When a native method is called from 1011JavaScript, a default handle scope will exist. If the user does not explicitly 1012create a new handle scope, Node-API values will be created in the default handle 1013scope. For any invocations of code outside the execution of a native method 1014(for instance, during a libuv callback invocation), the module is required to 1015create a scope before invoking any functions that can result in the creation 1016of JavaScript values.</p> 1017<p>Handle scopes are created using <a href="#n_api_napi_open_handle_scope"><code>napi_open_handle_scope</code></a> and are destroyed 1018using <a href="#n_api_napi_close_handle_scope"><code>napi_close_handle_scope</code></a>. Closing the scope can indicate to the GC 1019that all <code>napi_value</code>s created during the lifetime of the handle scope are no 1020longer referenced from the current stack frame.</p> 1021<p>For more details, review the <a href="#n_api_object_lifetime_management">Object lifetime management</a>.</p> 1022<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> 1023<div class="api_metadata"> 1024<span>Added in: v8.0.0</span> 1025<span>N-API version: 1</span> 1026</div> 1027<p>Escapable handle scopes are a special type of handle scope to return values 1028created within a particular handle scope to a parent scope.</p> 1029<h5>napi_ref<span><a class="mark" href="#n_api_napi_ref" id="n_api_napi_ref">#</a></span></h5> 1030<div class="api_metadata"> 1031<span>Added in: v8.0.0</span> 1032<span>N-API version: 1</span> 1033</div> 1034<p>This is the abstraction to use to reference a <code>napi_value</code>. This allows for 1035users to manage the lifetimes of JavaScript values, including defining their 1036minimum lifetimes explicitly.</p> 1037<p>For more details, review the <a href="#n_api_object_lifetime_management">Object lifetime management</a>.</p> 1038<h5>napi_type_tag<span><a class="mark" href="#n_api_napi_type_tag" id="n_api_napi_type_tag">#</a></span></h5> 1039<div class="api_metadata"> 1040<span>Added in: v14.8.0, v12.19.0</span> 1041<span>N-API version: 8</span> 1042</div> 1043<p>A 128-bit value stored as two unsigned 64-bit integers. It serves as a UUID 1044with which JavaScript objects can be "tagged" in order to ensure that they are 1045of a certain type. This is a stronger check than <a href="#n_api_napi_instanceof"><code>napi_instanceof</code></a>, because 1046the latter can report a false positive if the object's prototype has been 1047manipulated. Type-tagging is most useful in conjunction with <a href="#n_api_napi_wrap"><code>napi_wrap</code></a> 1048because it ensures that the pointer retrieved from a wrapped object can be 1049safely cast to the native type corresponding to the type tag that had been 1050previously applied to the JavaScript object.</p> 1051<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 1052 <span class="hljs-type">uint64_t</span> lower; 1053 <span class="hljs-type">uint64_t</span> upper; 1054} napi_type_tag;</code></pre> 1055<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> 1056<div class="api_metadata"> 1057<span>Added in: v14.10.0</span> 1058</div> 1059<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 1060to <a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a> when the chain of asynchronous cleanup 1061events completes.</p> 1062<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> 1063<h5>napi_callback_info<span><a class="mark" href="#n_api_napi_callback_info" id="n_api_napi_callback_info">#</a></span></h5> 1064<div class="api_metadata"> 1065<span>Added in: v8.0.0</span> 1066<span>N-API version: 1</span> 1067</div> 1068<p>Opaque datatype that is passed to a callback function. It can be used for 1069getting additional information about the context in which the callback was 1070invoked.</p> 1071<h5>napi_callback<span><a class="mark" href="#n_api_napi_callback" id="n_api_napi_callback">#</a></span></h5> 1072<div class="api_metadata"> 1073<span>Added in: v8.0.0</span> 1074<span>N-API version: 1</span> 1075</div> 1076<p>Function pointer type for user-provided native functions which are to be 1077exposed to JavaScript via Node-API. Callback functions should satisfy the 1078following signature:</p> 1079<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> 1080<p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1081handle and/or callback scope inside a <code>napi_callback</code> is not necessary.</p> 1082<h5>napi_finalize<span><a class="mark" href="#n_api_napi_finalize" id="n_api_napi_finalize">#</a></span></h5> 1083<div class="api_metadata"> 1084<span>Added in: v8.0.0</span> 1085<span>N-API version: 1</span> 1086</div> 1087<p>Function pointer type for add-on provided functions that allow the user to be 1088notified when externally-owned data is ready to be cleaned up because the 1089object with which it was associated with, has been garbage-collected. The user 1090must provide a function satisfying the following signature which would get 1091called upon the object's collection. Currently, <code>napi_finalize</code> can be used for 1092finding out when objects that have external data are collected.</p> 1093<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, 1094 <span class="hljs-type">void</span>* finalize_data, 1095 <span class="hljs-type">void</span>* finalize_hint)</span>;</code></pre> 1096<p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1097handle and/or callback scope inside the function body is not necessary.</p> 1098<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> 1099<div class="api_metadata"> 1100<span>Added in: v8.0.0</span> 1101<span>N-API version: 1</span> 1102</div> 1103<p>Function pointer used with functions that support asynchronous 1104operations. Callback functions must satisfy the following signature:</p> 1105<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> 1106<p>Implementations of this function must avoid making Node-API calls that execute 1107JavaScript or interact with JavaScript objects. Node-API calls should be in the 1108<code>napi_async_complete_callback</code> instead. Do not use the <code>napi_env</code> parameter as 1109it will likely result in execution of JavaScript.</p> 1110<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> 1111<div class="api_metadata"> 1112<span>Added in: v8.0.0</span> 1113<span>N-API version: 1</span> 1114</div> 1115<p>Function pointer used with functions that support asynchronous 1116operations. Callback functions must satisfy the following signature:</p> 1117<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, 1118 napi_status status, 1119 <span class="hljs-type">void</span>* data)</span>;</code></pre> 1120<p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1121handle and/or callback scope inside the function body is not necessary.</p> 1122<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> 1123<div class="api_metadata"> 1124<span>Added in: v10.6.0</span> 1125<span>N-API version: 4</span> 1126</div> 1127<p>Function pointer used with asynchronous thread-safe function calls. The callback 1128will be called on the main thread. Its purpose is to use a data item arriving 1129via the queue from one of the secondary threads to construct the parameters 1130necessary for a call into JavaScript, usually via <code>napi_call_function</code>, and then 1131make the call into JavaScript.</p> 1132<p>The data arriving from the secondary thread via the queue is given in the <code>data</code> 1133parameter and the JavaScript function to call is given in the <code>js_callback</code> 1134parameter.</p> 1135<p>Node-API sets up the environment prior to calling this callback, so it is 1136sufficient to call the JavaScript function via <code>napi_call_function</code> rather than 1137via <code>napi_make_callback</code>.</p> 1138<p>Callback functions must satisfy the following signature:</p> 1139<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, 1140 napi_value js_callback, 1141 <span class="hljs-type">void</span>* context, 1142 <span class="hljs-type">void</span>* data)</span>;</code></pre> 1143<ul> 1144<li><code>[in] env</code>: The environment to use for API calls, or <code>NULL</code> if the thread-safe 1145function is being torn down and <code>data</code> may need to be freed.</li> 1146<li><code>[in] js_callback</code>: The JavaScript function to call, or <code>NULL</code> if the 1147thread-safe function is being torn down and <code>data</code> may need to be freed. It 1148may also be <code>NULL</code> if the thread-safe function was created without 1149<code>js_callback</code>.</li> 1150<li><code>[in] context</code>: The optional data with which the thread-safe function was 1151created.</li> 1152<li><code>[in] data</code>: Data created by the secondary thread. It is the responsibility of 1153the callback to convert this native data to JavaScript values (with Node-API 1154functions) that can be passed as parameters when <code>js_callback</code> is invoked. 1155This pointer is managed entirely by the threads and this callback. Thus this 1156callback should free the data.</li> 1157</ul> 1158<p>Unless for reasons discussed in <a href="#n_api_object_lifetime_management">Object Lifetime Management</a>, creating a 1159handle and/or callback scope inside the function body is not necessary.</p> 1160<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> 1161<div class="api_metadata"> 1162<span>Added in: v14.10.0</span> 1163</div> 1164<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 1165when the environment is being torn down.</p> 1166<p>Callback functions must satisfy the following signature:</p> 1167<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, 1168 <span class="hljs-type">void</span>* data)</span>;</code></pre> 1169<ul> 1170<li><code>[in] handle</code>: The handle that must be passed to 1171<a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a> after completion of the asynchronous 1172cleanup.</li> 1173<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> 1174</ul> 1175<p>The body of the function should initiate the asynchronous cleanup actions at the 1176end of which <code>handle</code> must be passed in a call to 1177<a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a>.</p> 1178</section><section><h3>Error handling<span><a class="mark" href="#n_api_error_handling" id="n_api_error_handling">#</a></span></h3> 1179<p>Node-API uses both return values and JavaScript exceptions for error handling. 1180The following sections explain the approach for each case.</p> 1181<h4>Return values<span><a class="mark" href="#n_api_return_values" id="n_api_return_values">#</a></span></h4> 1182<p>All of the Node-API functions share the same error handling pattern. The 1183return type of all API functions is <code>napi_status</code>.</p> 1184<p>The return value will be <code>napi_ok</code> if the request was successful and 1185no uncaught JavaScript exception was thrown. If an error occurred AND 1186an exception was thrown, the <code>napi_status</code> value for the error 1187will be returned. If an exception was thrown, and no error occurred, 1188<code>napi_pending_exception</code> will be returned.</p> 1189<p>In cases where a return value other than <code>napi_ok</code> or 1190<code>napi_pending_exception</code> is returned, <a href="#n_api_napi_is_exception_pending"><code>napi_is_exception_pending</code></a> 1191must be called to check if an exception is pending. 1192See the section on exceptions for more details.</p> 1193<p>The full set of possible <code>napi_status</code> values is defined 1194in <code>napi_api_types.h</code>.</p> 1195<p>The <code>napi_status</code> return value provides a VM-independent representation of 1196the error which occurred. In some cases it is useful to be able to get 1197more detailed information, including a string representing the error as well as 1198VM (engine)-specific information.</p> 1199<p>In order to retrieve this information <a href="#n_api_napi_get_last_error_info"><code>napi_get_last_error_info</code></a> 1200is provided which returns a <code>napi_extended_error_info</code> structure. 1201The format of the <code>napi_extended_error_info</code> structure is as follows:</p> 1202<div class="api_metadata"> 1203<span>Added in: v8.0.0</span> 1204<span>N-API version: 1</span> 1205</div> 1206<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> 1207 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* error_message; 1208 <span class="hljs-type">void</span>* engine_reserved; 1209 <span class="hljs-type">uint32_t</span> engine_error_code; 1210 napi_status error_code; 1211};</code></pre> 1212<ul> 1213<li><code>error_message</code>: Textual representation of the error that occurred.</li> 1214<li><code>engine_reserved</code>: Opaque handle reserved for engine use only.</li> 1215<li><code>engine_error_code</code>: VM specific error code.</li> 1216<li><code>error_code</code>: Node-API status code for the last error.</li> 1217</ul> 1218<p><a href="#n_api_napi_get_last_error_info"><code>napi_get_last_error_info</code></a> returns the information for the last 1219Node-API call that was made.</p> 1220<p>Do not rely on the content or format of any of the extended information as it 1221is not subject to SemVer and may change at any time. It is intended only for 1222logging purposes.</p> 1223<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> 1224<div class="api_metadata"> 1225<span>Added in: v8.0.0</span> 1226<span>N-API version: 1</span> 1227</div> 1228<pre><code class="language-c">napi_status 1229<span class="hljs-title function_">napi_get_last_error_info</span><span class="hljs-params">(napi_env env, 1230 <span class="hljs-keyword">const</span> napi_extended_error_info** result)</span>;</code></pre> 1231<ul> 1232<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1233<li><code>[out] result</code>: The <code>napi_extended_error_info</code> structure with more 1234information about the error.</li> 1235</ul> 1236<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1237<p>This API retrieves a <code>napi_extended_error_info</code> structure with information 1238about the last error that occurred.</p> 1239<p>The content of the <code>napi_extended_error_info</code> returned is only valid up until 1240a Node-API function is called on the same <code>env</code>.</p> 1241<p>Do not rely on the content or format of any of the extended information as it 1242is not subject to SemVer and may change at any time. It is intended only for 1243logging purposes.</p> 1244<p>This API can be called even if there is a pending JavaScript exception.</p> 1245<h4>Exceptions<span><a class="mark" href="#n_api_exceptions" id="n_api_exceptions">#</a></span></h4> 1246<p>Any Node-API function call may result in a pending JavaScript exception. This is 1247the case for any of the API functions, even those that may not cause the 1248execution of JavaScript.</p> 1249<p>If the <code>napi_status</code> returned by a function is <code>napi_ok</code> then no 1250exception is pending and no additional action is required. If the 1251<code>napi_status</code> returned is anything other than <code>napi_ok</code> or 1252<code>napi_pending_exception</code>, in order to try to recover and continue 1253instead of simply returning immediately, <a href="#n_api_napi_is_exception_pending"><code>napi_is_exception_pending</code></a> 1254must be called in order to determine if an exception is pending or not.</p> 1255<p>In many cases when a Node-API function is called and an exception is 1256already pending, the function will return immediately with a 1257<code>napi_status</code> of <code>napi_pending_exception</code>. However, this is not the case 1258for all functions. Node-API allows a subset of the functions to be 1259called to allow for some minimal cleanup before returning to JavaScript. 1260In that case, <code>napi_status</code> will reflect the status for the function. It 1261will not reflect previous pending exceptions. To avoid confusion, check 1262the error status after every function call.</p> 1263<p>When an exception is pending one of two approaches can be employed.</p> 1264<p>The first approach is to do any appropriate cleanup and then return so that 1265execution will return to JavaScript. As part of the transition back to 1266JavaScript, the exception will be thrown at the point in the JavaScript 1267code where the native method was invoked. The behavior of most Node-API calls 1268is unspecified while an exception is pending, and many will simply return 1269<code>napi_pending_exception</code>, so do as little as possible and then return to 1270JavaScript where the exception can be handled.</p> 1271<p>The second approach is to try to handle the exception. There will be cases 1272where the native code can catch the exception, take the appropriate action, 1273and then continue. This is only recommended in specific cases 1274where it is known that the exception can be safely handled. In these 1275cases <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 1276clear the exception. On success, result will contain the handle to 1277the last JavaScript <code>Object</code> thrown. If it is determined, after 1278retrieving the exception, the exception cannot be handled after all 1279it can be re-thrown it with <a href="#n_api_napi_throw"><code>napi_throw</code></a> where error is the 1280JavaScript value to be thrown.</p> 1281<p>The following utility functions are also available in case native code 1282needs to throw an exception or determine if a <code>napi_value</code> is an instance 1283of a JavaScript <code>Error</code> object: <a href="#n_api_napi_throw_error"><code>napi_throw_error</code></a>, 1284<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 1285<a href="#n_api_napi_is_error"><code>napi_is_error</code></a>.</p> 1286<p>The following utility functions are also available in case native 1287code needs to create an <code>Error</code> object: <a href="#n_api_napi_create_error"><code>napi_create_error</code></a>, 1288<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>, 1289where result is the <code>napi_value</code> that refers to the newly created 1290JavaScript <code>Error</code> object.</p> 1291<p>The Node.js project is adding error codes to all of the errors 1292generated internally. The goal is for applications to use these 1293error codes for all error checking. The associated error messages 1294will remain, but will only be meant to be used for logging and 1295display with the expectation that the message can change without 1296SemVer applying. In order to support this model with Node-API, both 1297in internal functionality and for module specific functionality 1298(as its good practice), the <code>throw_</code> and <code>create_</code> functions 1299take an optional code parameter which is the string for the code 1300to be added to the error object. If the optional parameter is <code>NULL</code> 1301then no code will be associated with the error. If a code is provided, 1302the name associated with the error is also updated to be:</p> 1303<pre><code class="language-text">originalName [code]</code></pre> 1304<p>where <code>originalName</code> is the original name associated with the error 1305and <code>code</code> is the code that was provided. For example, if the code 1306is <code>'ERR_ERROR_1'</code> and a <code>TypeError</code> is being created the name will be:</p> 1307<pre><code class="language-text">TypeError [ERR_ERROR_1]</code></pre> 1308<h5>napi_throw<span><a class="mark" href="#n_api_napi_throw" id="n_api_napi_throw">#</a></span></h5> 1309<div class="api_metadata"> 1310<span>Added in: v8.0.0</span> 1311<span>N-API version: 1</span> 1312</div> 1313<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> 1314<ul> 1315<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1316<li><code>[in] error</code>: The JavaScript value to be thrown.</li> 1317</ul> 1318<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1319<p>This API throws the JavaScript value provided.</p> 1320<h5>napi_throw_error<span><a class="mark" href="#n_api_napi_throw_error" id="n_api_napi_throw_error">#</a></span></h5> 1321<div class="api_metadata"> 1322<span>Added in: v8.0.0</span> 1323<span>N-API version: 1</span> 1324</div> 1325<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, 1326 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* code, 1327 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* msg)</span>;</code></pre> 1328<ul> 1329<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1330<li><code>[in] code</code>: Optional error code to be set on the error.</li> 1331<li><code>[in] msg</code>: C string representing the text to be associated with the error.</li> 1332</ul> 1333<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1334<p>This API throws a JavaScript <code>Error</code> with the text provided.</p> 1335<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> 1336<div class="api_metadata"> 1337<span>Added in: v8.0.0</span> 1338<span>N-API version: 1</span> 1339</div> 1340<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, 1341 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* code, 1342 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* msg)</span>;</code></pre> 1343<ul> 1344<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1345<li><code>[in] code</code>: Optional error code to be set on the error.</li> 1346<li><code>[in] msg</code>: C string representing the text to be associated with the error.</li> 1347</ul> 1348<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1349<p>This API throws a JavaScript <code>TypeError</code> with the text provided.</p> 1350<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> 1351<div class="api_metadata"> 1352<span>Added in: v8.0.0</span> 1353<span>N-API version: 1</span> 1354</div> 1355<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, 1356 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* code, 1357 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* msg)</span>;</code></pre> 1358<ul> 1359<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1360<li><code>[in] code</code>: Optional error code to be set on the error.</li> 1361<li><code>[in] msg</code>: C string representing the text to be associated with the error.</li> 1362</ul> 1363<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1364<p>This API throws a JavaScript <code>RangeError</code> with the text provided.</p> 1365<h5>napi_is_error<span><a class="mark" href="#n_api_napi_is_error" id="n_api_napi_is_error">#</a></span></h5> 1366<div class="api_metadata"> 1367<span>Added in: v8.0.0</span> 1368<span>N-API version: 1</span> 1369</div> 1370<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, 1371 napi_value value, 1372 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 1373<ul> 1374<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1375<li><code>[in] value</code>: The <code>napi_value</code> to be checked.</li> 1376<li><code>[out] result</code>: Boolean value that is set to true if <code>napi_value</code> represents 1377an error, false otherwise.</li> 1378</ul> 1379<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1380<p>This API queries a <code>napi_value</code> to check if it represents an error object.</p> 1381<h5>napi_create_error<span><a class="mark" href="#n_api_napi_create_error" id="n_api_napi_create_error">#</a></span></h5> 1382<div class="api_metadata"> 1383<span>Added in: v8.0.0</span> 1384<span>N-API version: 1</span> 1385</div> 1386<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, 1387 napi_value code, 1388 napi_value msg, 1389 napi_value* result)</span>;</code></pre> 1390<ul> 1391<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1392<li><code>[in] code</code>: Optional <code>napi_value</code> with the string for the error code to be 1393associated with the error.</li> 1394<li><code>[in] msg</code>: <code>napi_value</code> that references a JavaScript <code>string</code> to be used as 1395the message for the <code>Error</code>.</li> 1396<li><code>[out] result</code>: <code>napi_value</code> representing the error created.</li> 1397</ul> 1398<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1399<p>This API returns a JavaScript <code>Error</code> with the text provided.</p> 1400<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> 1401<div class="api_metadata"> 1402<span>Added in: v8.0.0</span> 1403<span>N-API version: 1</span> 1404</div> 1405<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, 1406 napi_value code, 1407 napi_value msg, 1408 napi_value* result)</span>;</code></pre> 1409<ul> 1410<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1411<li><code>[in] code</code>: Optional <code>napi_value</code> with the string for the error code to be 1412associated with the error.</li> 1413<li><code>[in] msg</code>: <code>napi_value</code> that references a JavaScript <code>string</code> to be used as 1414the message for the <code>Error</code>.</li> 1415<li><code>[out] result</code>: <code>napi_value</code> representing the error created.</li> 1416</ul> 1417<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1418<p>This API returns a JavaScript <code>TypeError</code> with the text provided.</p> 1419<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> 1420<div class="api_metadata"> 1421<span>Added in: v8.0.0</span> 1422<span>N-API version: 1</span> 1423</div> 1424<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, 1425 napi_value code, 1426 napi_value msg, 1427 napi_value* result)</span>;</code></pre> 1428<ul> 1429<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1430<li><code>[in] code</code>: Optional <code>napi_value</code> with the string for the error code to be 1431associated with the error.</li> 1432<li><code>[in] msg</code>: <code>napi_value</code> that references a JavaScript <code>string</code> to be used as 1433the message for the <code>Error</code>.</li> 1434<li><code>[out] result</code>: <code>napi_value</code> representing the error created.</li> 1435</ul> 1436<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1437<p>This API returns a JavaScript <code>RangeError</code> with the text provided.</p> 1438<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> 1439<div class="api_metadata"> 1440<span>Added in: v8.0.0</span> 1441<span>N-API version: 1</span> 1442</div> 1443<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, 1444 napi_value* result)</span>;</code></pre> 1445<ul> 1446<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1447<li><code>[out] result</code>: The exception if one is pending, <code>NULL</code> otherwise.</li> 1448</ul> 1449<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1450<p>This API can be called even if there is a pending JavaScript exception.</p> 1451<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> 1452<div class="api_metadata"> 1453<span>Added in: v8.0.0</span> 1454<span>N-API version: 1</span> 1455</div> 1456<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> 1457<ul> 1458<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1459<li><code>[out] result</code>: Boolean value that is set to true if an exception is pending.</li> 1460</ul> 1461<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1462<p>This API can be called even if there is a pending JavaScript exception.</p> 1463<h5>napi_fatal_exception<span><a class="mark" href="#n_api_napi_fatal_exception" id="n_api_napi_fatal_exception">#</a></span></h5> 1464<div class="api_metadata"> 1465<span>Added in: v9.10.0</span> 1466<span>N-API version: 3</span> 1467</div> 1468<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> 1469<ul> 1470<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1471<li><code>[in] err</code>: The error that is passed to <code>'uncaughtException'</code>.</li> 1472</ul> 1473<p>Trigger an <code>'uncaughtException'</code> in JavaScript. Useful if an async 1474callback throws an exception with no way to recover.</p> 1475<h4>Fatal errors<span><a class="mark" href="#n_api_fatal_errors" id="n_api_fatal_errors">#</a></span></h4> 1476<p>In the event of an unrecoverable error in a native module, a fatal error can be 1477thrown to immediately terminate the process.</p> 1478<h5>napi_fatal_error<span><a class="mark" href="#n_api_napi_fatal_error" id="n_api_napi_fatal_error">#</a></span></h5> 1479<div class="api_metadata"> 1480<span>Added in: v8.2.0</span> 1481<span>N-API version: 1</span> 1482</div> 1483<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, 1484 <span class="hljs-type">size_t</span> location_len, 1485 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* message, 1486 <span class="hljs-type">size_t</span> message_len)</span>;</code></pre> 1487<ul> 1488<li><code>[in] location</code>: Optional location at which the error occurred.</li> 1489<li><code>[in] location_len</code>: The length of the location in bytes, or 1490<code>NAPI_AUTO_LENGTH</code> if it is null-terminated.</li> 1491<li><code>[in] message</code>: The message associated with the error.</li> 1492<li><code>[in] message_len</code>: The length of the message in bytes, or <code>NAPI_AUTO_LENGTH</code> 1493if it is null-terminated.</li> 1494</ul> 1495<p>The function call does not return, the process will be terminated.</p> 1496<p>This API can be called even if there is a pending JavaScript exception.</p> 1497</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> 1498<p>As Node-API calls are made, handles to objects in the heap for the underlying 1499VM may be returned as <code>napi_values</code>. These handles must hold the 1500objects 'live' until they are no longer required by the native code, 1501otherwise the objects could be collected before the native code was 1502finished using them.</p> 1503<p>As object handles are returned they are associated with a 1504'scope'. The lifespan for the default scope is tied to the lifespan 1505of the native method call. The result is that, by default, handles 1506remain valid and the objects associated with these handles will be 1507held live for the lifespan of the native method call.</p> 1508<p>In many cases, however, it is necessary that the handles remain valid for 1509either a shorter or longer lifespan than that of the native method. 1510The sections which follow describe the Node-API functions that can be used 1511to change the handle lifespan from the default.</p> 1512<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> 1513<p>It is often necessary to make the lifespan of handles shorter than 1514the lifespan of a native method. For example, consider a native method 1515that has a loop which iterates through the elements in a large array:</p> 1516<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++) { 1517 napi_value result; 1518 napi_status status = napi_get_element(env, object, i, &result); 1519 <span class="hljs-keyword">if</span> (status != napi_ok) { 1520 <span class="hljs-keyword">break</span>; 1521 } 1522 <span class="hljs-comment">// do something with element</span> 1523}</code></pre> 1524<p>This would result in a large number of handles being created, consuming 1525substantial resources. In addition, even though the native code could only 1526use the most recent handle, all of the associated objects would also be 1527kept alive since they all share the same scope.</p> 1528<p>To handle this case, Node-API provides the ability to establish a new 'scope' to 1529which newly created handles will be associated. Once those handles 1530are no longer required, the scope can be 'closed' and any handles associated 1531with the scope are invalidated. The methods available to open/close scopes are 1532<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> 1533<p>Node-API only supports a single nested hierarchy of scopes. There is only one 1534active scope at any time, and all new handles will be associated with that 1535scope while it is active. Scopes must be closed in the reverse order from 1536which they are opened. In addition, all scopes created within a native method 1537must be closed before returning from that method.</p> 1538<p>Taking the earlier example, adding calls to <a href="#n_api_napi_open_handle_scope"><code>napi_open_handle_scope</code></a> and 1539<a href="#n_api_napi_close_handle_scope"><code>napi_close_handle_scope</code></a> would ensure that at most a single handle 1540is valid throughout the execution of the loop:</p> 1541<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++) { 1542 napi_handle_scope scope; 1543 napi_status status = napi_open_handle_scope(env, &scope); 1544 <span class="hljs-keyword">if</span> (status != napi_ok) { 1545 <span class="hljs-keyword">break</span>; 1546 } 1547 napi_value result; 1548 status = napi_get_element(env, object, i, &result); 1549 <span class="hljs-keyword">if</span> (status != napi_ok) { 1550 <span class="hljs-keyword">break</span>; 1551 } 1552 <span class="hljs-comment">// do something with element</span> 1553 status = napi_close_handle_scope(env, scope); 1554 <span class="hljs-keyword">if</span> (status != napi_ok) { 1555 <span class="hljs-keyword">break</span>; 1556 } 1557}</code></pre> 1558<p>When nesting scopes, there are cases where a handle from an 1559inner scope needs to live beyond the lifespan of that scope. Node-API supports 1560an 'escapable scope' in order to support this case. An escapable scope 1561allows one handle to be 'promoted' so that it 'escapes' the 1562current scope and the lifespan of the handle changes from the current 1563scope to that of the outer scope.</p> 1564<p>The methods available to open/close escapable scopes are 1565<a href="#n_api_napi_open_escapable_handle_scope"><code>napi_open_escapable_handle_scope</code></a> and 1566<a href="#n_api_napi_close_escapable_handle_scope"><code>napi_close_escapable_handle_scope</code></a>.</p> 1567<p>The request to promote a handle is made through <a href="#n_api_napi_escape_handle"><code>napi_escape_handle</code></a> which 1568can only be called once.</p> 1569<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> 1570<div class="api_metadata"> 1571<span>Added in: v8.0.0</span> 1572<span>N-API version: 1</span> 1573</div> 1574<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, 1575 napi_handle_scope* result)</span>;</code></pre> 1576<ul> 1577<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1578<li><code>[out] result</code>: <code>napi_value</code> representing the new scope.</li> 1579</ul> 1580<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1581<p>This API opens a new scope.</p> 1582<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> 1583<div class="api_metadata"> 1584<span>Added in: v8.0.0</span> 1585<span>N-API version: 1</span> 1586</div> 1587<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, 1588 napi_handle_scope scope)</span>;</code></pre> 1589<ul> 1590<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1591<li><code>[in] scope</code>: <code>napi_value</code> representing the scope to be closed.</li> 1592</ul> 1593<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1594<p>This API closes the scope passed in. Scopes must be closed in the 1595reverse order from which they were created.</p> 1596<p>This API can be called even if there is a pending JavaScript exception.</p> 1597<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> 1598<div class="api_metadata"> 1599<span>Added in: v8.0.0</span> 1600<span>N-API version: 1</span> 1601</div> 1602<pre><code class="language-c">NAPI_EXTERN napi_status 1603 <span class="hljs-title function_">napi_open_escapable_handle_scope</span><span class="hljs-params">(napi_env env, 1604 napi_handle_scope* result)</span>;</code></pre> 1605<ul> 1606<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1607<li><code>[out] result</code>: <code>napi_value</code> representing the new scope.</li> 1608</ul> 1609<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1610<p>This API opens a new scope from which one object can be promoted 1611to the outer scope.</p> 1612<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> 1613<div class="api_metadata"> 1614<span>Added in: v8.0.0</span> 1615<span>N-API version: 1</span> 1616</div> 1617<pre><code class="language-c">NAPI_EXTERN napi_status 1618 <span class="hljs-title function_">napi_close_escapable_handle_scope</span><span class="hljs-params">(napi_env env, 1619 napi_handle_scope scope)</span>;</code></pre> 1620<ul> 1621<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1622<li><code>[in] scope</code>: <code>napi_value</code> representing the scope to be closed.</li> 1623</ul> 1624<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1625<p>This API closes the scope passed in. Scopes must be closed in the 1626reverse order from which they were created.</p> 1627<p>This API can be called even if there is a pending JavaScript exception.</p> 1628<h5>napi_escape_handle<span><a class="mark" href="#n_api_napi_escape_handle" id="n_api_napi_escape_handle">#</a></span></h5> 1629<div class="api_metadata"> 1630<span>Added in: v8.0.0</span> 1631<span>N-API version: 1</span> 1632</div> 1633<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_escape_handle</span><span class="hljs-params">(napi_env env, 1634 napi_escapable_handle_scope scope, 1635 napi_value escapee, 1636 napi_value* result)</span>;</code></pre> 1637<ul> 1638<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1639<li><code>[in] scope</code>: <code>napi_value</code> representing the current scope.</li> 1640<li><code>[in] escapee</code>: <code>napi_value</code> representing the JavaScript <code>Object</code> to be 1641escaped.</li> 1642<li><code>[out] result</code>: <code>napi_value</code> representing the handle to the escaped <code>Object</code> 1643in the outer scope.</li> 1644</ul> 1645<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1646<p>This API promotes the handle to the JavaScript object so that it is valid 1647for the lifetime of the outer scope. It can only be called once per scope. 1648If it is called more than once an error will be returned.</p> 1649<p>This API can be called even if there is a pending JavaScript exception.</p> 1650<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> 1651<p>In some cases an addon will need to be able to create and reference objects 1652with a lifespan longer than that of a single native method invocation. For 1653example, to create a constructor and later use that constructor 1654in a request to creates instances, it must be possible to reference 1655the constructor object across many different instance creation requests. This 1656would not be possible with a normal handle returned as a <code>napi_value</code> as 1657described in the earlier section. The lifespan of a normal handle is 1658managed by scopes and all scopes must be closed before the end of a native 1659method.</p> 1660<p>Node-API provides methods to create persistent references to an object. 1661Each persistent reference has an associated count with a value of 0 1662or higher. The count determines if the reference will keep 1663the corresponding object live. References with a count of 0 do not 1664prevent the object from being collected and are often called 'weak' 1665references. Any count greater than 0 will prevent the object 1666from being collected.</p> 1667<p>References can be created with an initial reference count. The count can 1668then be modified through <a href="#n_api_napi_reference_ref"><code>napi_reference_ref</code></a> and 1669<a href="#n_api_napi_reference_unref"><code>napi_reference_unref</code></a>. If an object is collected while the count 1670for a reference is 0, all subsequent calls to 1671get the object associated with the reference <a href="#n_api_napi_get_reference_value"><code>napi_get_reference_value</code></a> 1672will return <code>NULL</code> for the returned <code>napi_value</code>. An attempt to call 1673<a href="#n_api_napi_reference_ref"><code>napi_reference_ref</code></a> for a reference whose object has been collected 1674results in an error.</p> 1675<p>References must be deleted once they are no longer required by the addon. When 1676a reference is deleted, it will no longer prevent the corresponding object from 1677being collected. Failure to delete a persistent reference results in 1678a 'memory leak' with both the native memory for the persistent reference and 1679the corresponding object on the heap being retained forever.</p> 1680<p>There can be multiple persistent references created which refer to the same 1681object, each of which will either keep the object live or not based on its 1682individual count.</p> 1683<h5>napi_create_reference<span><a class="mark" href="#n_api_napi_create_reference" id="n_api_napi_create_reference">#</a></span></h5> 1684<div class="api_metadata"> 1685<span>Added in: v8.0.0</span> 1686<span>N-API version: 1</span> 1687</div> 1688<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, 1689 napi_value value, 1690 <span class="hljs-type">uint32_t</span> initial_refcount, 1691 napi_ref* result)</span>;</code></pre> 1692<ul> 1693<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1694<li><code>[in] value</code>: <code>napi_value</code> representing the <code>Object</code> to which we want a 1695reference.</li> 1696<li><code>[in] initial_refcount</code>: Initial reference count for the new reference.</li> 1697<li><code>[out] result</code>: <code>napi_ref</code> pointing to the new reference.</li> 1698</ul> 1699<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1700<p>This API create a new reference with the specified reference count 1701to the <code>Object</code> passed in.</p> 1702<h5>napi_delete_reference<span><a class="mark" href="#n_api_napi_delete_reference" id="n_api_napi_delete_reference">#</a></span></h5> 1703<div class="api_metadata"> 1704<span>Added in: v8.0.0</span> 1705<span>N-API version: 1</span> 1706</div> 1707<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> 1708<ul> 1709<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1710<li><code>[in] ref</code>: <code>napi_ref</code> to be deleted.</li> 1711</ul> 1712<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1713<p>This API deletes the reference passed in.</p> 1714<p>This API can be called even if there is a pending JavaScript exception.</p> 1715<h5>napi_reference_ref<span><a class="mark" href="#n_api_napi_reference_ref" id="n_api_napi_reference_ref">#</a></span></h5> 1716<div class="api_metadata"> 1717<span>Added in: v8.0.0</span> 1718<span>N-API version: 1</span> 1719</div> 1720<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, 1721 napi_ref ref, 1722 <span class="hljs-type">uint32_t</span>* result)</span>;</code></pre> 1723<ul> 1724<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1725<li><code>[in] ref</code>: <code>napi_ref</code> for which the reference count will be incremented.</li> 1726<li><code>[out] result</code>: The new reference count.</li> 1727</ul> 1728<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1729<p>This API increments the reference count for the reference 1730passed in and returns the resulting reference count.</p> 1731<h5>napi_reference_unref<span><a class="mark" href="#n_api_napi_reference_unref" id="n_api_napi_reference_unref">#</a></span></h5> 1732<div class="api_metadata"> 1733<span>Added in: v8.0.0</span> 1734<span>N-API version: 1</span> 1735</div> 1736<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, 1737 napi_ref ref, 1738 <span class="hljs-type">uint32_t</span>* result)</span>;</code></pre> 1739<ul> 1740<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1741<li><code>[in] ref</code>: <code>napi_ref</code> for which the reference count will be decremented.</li> 1742<li><code>[out] result</code>: The new reference count.</li> 1743</ul> 1744<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1745<p>This API decrements the reference count for the reference 1746passed in and returns the resulting reference count.</p> 1747<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> 1748<div class="api_metadata"> 1749<span>Added in: v8.0.0</span> 1750<span>N-API version: 1</span> 1751</div> 1752<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, 1753 napi_ref ref, 1754 napi_value* result)</span>;</code></pre> 1755<p>the <code>napi_value passed</code> in or out of these methods is a handle to the 1756object to which the reference is related.</p> 1757<ul> 1758<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1759<li><code>[in] ref</code>: <code>napi_ref</code> for which we requesting the corresponding <code>Object</code>.</li> 1760<li><code>[out] result</code>: The <code>napi_value</code> for the <code>Object</code> referenced by the 1761<code>napi_ref</code>.</li> 1762</ul> 1763<p>Returns <code>napi_ok</code> if the API succeeded.</p> 1764<p>If still valid, this API returns the <code>napi_value</code> representing the 1765JavaScript <code>Object</code> associated with the <code>napi_ref</code>. Otherwise, result 1766will be <code>NULL</code>.</p> 1767<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> 1768<p>While a Node.js process typically releases all its resources when exiting, 1769embedders of Node.js, or future Worker support, may require addons to register 1770clean-up hooks that will be run once the current Node.js instance exits.</p> 1771<p>Node-API provides functions for registering and un-registering such callbacks. 1772When those callbacks are run, all resources that are being held by the addon 1773should be freed up.</p> 1774<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> 1775<div class="api_metadata"> 1776<span>Added in: v10.2.0</span> 1777<span>N-API version: 3</span> 1778</div> 1779<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, 1780 <span class="hljs-type">void</span> (*fun)(<span class="hljs-type">void</span>* arg), 1781 <span class="hljs-type">void</span>* arg)</span>;</code></pre> 1782<p>Registers <code>fun</code> as a function to be run with the <code>arg</code> parameter once the 1783current Node.js environment exits.</p> 1784<p>A function can safely be specified multiple times with different 1785<code>arg</code> values. In that case, it will be called multiple times as well. 1786Providing the same <code>fun</code> and <code>arg</code> values multiple times is not allowed 1787and will lead the process to abort.</p> 1788<p>The hooks will be called in reverse order, i.e. the most recently added one 1789will be called first.</p> 1790<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>. 1791Typically, that happens when the resource for which this hook was added 1792is being torn down anyway.</p> 1793<p>For asynchronous cleanup, <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a> is available.</p> 1794<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> 1795<div class="api_metadata"> 1796<span>Added in: v10.2.0</span> 1797<span>N-API version: 3</span> 1798</div> 1799<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, 1800 <span class="hljs-type">void</span> (*fun)(<span class="hljs-type">void</span>* arg), 1801 <span class="hljs-type">void</span>* arg)</span>;</code></pre> 1802<p>Unregisters <code>fun</code> as a function to be run with the <code>arg</code> parameter once the 1803current Node.js environment exits. Both the argument and the function value 1804need to be exact matches.</p> 1805<p>The function must have originally been registered 1806with <code>napi_add_env_cleanup_hook</code>, otherwise the process will abort.</p> 1807<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> 1808<div class="api_metadata"> 1809<details class="changelog"><summary>History</summary> 1810<table> 1811<tbody><tr><th>Version</th><th>Changes</th></tr> 1812<tr><td>v14.10.0</td> 1813<td><p>Changed signature of the <code>hook</code> callback.</p></td></tr> 1814<tr><td>v14.8.0, v12.19.0</td> 1815<td><p><span>Added in: v14.8.0, v12.19.0</span></p></td></tr> 1816</tbody></table> 1817</details> 1818<span>N-API version: 8</span> 1819</div> 1820<pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_add_async_cleanup_hook</span><span class="hljs-params">( 1821 napi_env env, 1822 napi_async_cleanup_hook hook, 1823 <span class="hljs-type">void</span>* arg, 1824 napi_async_cleanup_hook_handle* remove_handle)</span>;</code></pre> 1825<ul> 1826<li><code>[in] env</code>: The environment that the API is invoked under.</li> 1827<li><code>[in] hook</code>: The function pointer to call at environment teardown.</li> 1828<li><code>[in] arg</code>: The pointer to pass to <code>hook</code> when it gets called.</li> 1829<li><code>[out] remove_handle</code>: Optional handle that refers to the asynchronous cleanup 1830hook.</li> 1831</ul> 1832<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 1833a function to be run with the <code>remove_handle</code> and <code>arg</code> parameters once the 1834current Node.js environment exits.</p> 1835<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> 1836<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> 1837<p>If <code>remove_handle</code> is not <code>NULL</code>, an opaque value will be stored in it 1838that must later be passed to <a href="#n_api_napi_remove_async_cleanup_hook"><code>napi_remove_async_cleanup_hook</code></a>, 1839regardless of whether the hook has already been invoked. 1840Typically, that happens when the resource for which this hook was added 1841is being torn down anyway.</p> 1842<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> 1843<div class="api_metadata"> 1844<details class="changelog"><summary>History</summary> 1845<table> 1846<tbody><tr><th>Version</th><th>Changes</th></tr> 1847<tr><td>v14.10.0</td> 1848<td><p>Removed <code>env</code> parameter.</p></td></tr> 1849<tr><td>v14.8.0</td> 1850<td><p><span>Added in: v14.8.0</span></p></td></tr> 1851</tbody></table> 1852</details> 1853</div> 1854<pre><code class="language-c">NAPI_EXTERN napi_status <span class="hljs-title function_">napi_remove_async_cleanup_hook</span><span class="hljs-params">( 1855 napi_async_cleanup_hook_handle remove_handle)</span>;</code></pre> 1856<ul> 1857<li><code>[in] remove_handle</code>: The handle to an asynchronous cleanup hook that was 1858created with <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a>.</li> 1859</ul> 1860<p>Unregisters the cleanup hook corresponding to <code>remove_handle</code>. This will prevent 1861the hook from being executed, unless it has already started executing. 1862This must be called on any <code>napi_async_cleanup_hook_handle</code> value obtained 1863from <a href="#n_api_napi_add_async_cleanup_hook"><code>napi_add_async_cleanup_hook</code></a>.</p> 1864</section><section><h3>Module registration<span><a class="mark" href="#n_api_module_registration" id="n_api_module_registration">#</a></span></h3> 1865<p>Node-API modules are registered in a manner similar to other modules 1866except that instead of using the <code>NODE_MODULE</code> macro the following 1867is used:</p> 1868<pre><code class="language-c">NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)</code></pre> 1869<p>The next difference is the signature for the <code>Init</code> method. For a Node-API 1870module it is as follows:</p> 1871<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> 1872<p>The return value from <code>Init</code> is treated as the <code>exports</code> object for the module. 1873The <code>Init</code> method is passed an empty object via the <code>exports</code> parameter as a 1874convenience. If <code>Init</code> returns <code>NULL</code>, the parameter passed as <code>exports</code> is 1875exported by the module. Node-API modules cannot modify the <code>module</code> object but 1876can specify anything as the <code>exports</code> property of the module.</p> 1877<p>To add the method <code>hello</code> as a function so that it can be called as a method 1878provided by the addon:</p> 1879<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> { 1880 napi_status status; 1881 napi_property_descriptor desc = { 1882 <span class="hljs-string">"hello"</span>, 1883 <span class="hljs-literal">NULL</span>, 1884 Method, 1885 <span class="hljs-literal">NULL</span>, 1886 <span class="hljs-literal">NULL</span>, 1887 <span class="hljs-literal">NULL</span>, 1888 napi_writable | napi_enumerable | napi_configurable, 1889 <span class="hljs-literal">NULL</span> 1890 }; 1891 status = napi_define_properties(env, exports, <span class="hljs-number">1</span>, &desc); 1892 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1893 <span class="hljs-keyword">return</span> exports; 1894}</code></pre> 1895<p>To set a function to be returned by the <code>require()</code> for the addon:</p> 1896<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> { 1897 napi_value method; 1898 napi_status status; 1899 status = napi_create_function(env, <span class="hljs-string">"exports"</span>, NAPI_AUTO_LENGTH, Method, <span class="hljs-literal">NULL</span>, &method); 1900 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1901 <span class="hljs-keyword">return</span> method; 1902}</code></pre> 1903<p>To define a class so that new instances can be created (often used with 1904<a href="#n_api_object_wrap">Object wrap</a>):</p> 1905<pre><code class="language-c"><span class="hljs-comment">// <span class="hljs-doctag">NOTE:</span> partial example, not all referenced code is included</span> 1906napi_value <span class="hljs-title function_">Init</span><span class="hljs-params">(napi_env env, napi_value exports)</span> { 1907 napi_status status; 1908 napi_property_descriptor properties[] = { 1909 { <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> }, 1910 DECLARE_NAPI_METHOD(<span class="hljs-string">"plusOne"</span>, PlusOne), 1911 DECLARE_NAPI_METHOD(<span class="hljs-string">"multiply"</span>, Multiply), 1912 }; 1913 1914 napi_value cons; 1915 status = 1916 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); 1917 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1918 1919 status = napi_create_reference(env, cons, <span class="hljs-number">1</span>, &constructor); 1920 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1921 1922 status = napi_set_named_property(env, exports, <span class="hljs-string">"MyObject"</span>, cons); 1923 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1924 1925 <span class="hljs-keyword">return</span> exports; 1926}</code></pre> 1927<p>You can also use the <code>NAPI_MODULE_INIT</code> macro, which acts as a shorthand 1928for <code>NAPI_MODULE</code> and defining an <code>Init</code> function:</p> 1929<pre><code class="language-c">NAPI_MODULE_INIT() { 1930 napi_value answer; 1931 napi_status result; 1932 1933 status = napi_create_int64(env, <span class="hljs-number">42</span>, &answer); 1934 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1935 1936 status = napi_set_named_property(env, exports, <span class="hljs-string">"answer"</span>, answer); 1937 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1938 1939 <span class="hljs-keyword">return</span> exports; 1940}</code></pre> 1941<p>All Node-API addons are context-aware, meaning they may be loaded multiple 1942times. There are a few design considerations when declaring such a module. 1943The documentation on <a href="addons.html#addons_context_aware_addons">context-aware addons</a> provides more details.</p> 1944<p>The variables <code>env</code> and <code>exports</code> will be available inside the function body 1945following the macro invocation.</p> 1946<p>For more details on setting properties on objects, see the section on 1947<a href="#n_api_working_with_javascript_properties">Working with JavaScript properties</a>.</p> 1948<p>For more details on building addon modules in general, refer to the existing 1949API.</p> 1950</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> 1951<p>Node-API exposes a set of APIs to create all types of JavaScript values. 1952Some of these types are documented under <a href="https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values">Section 6</a> 1953of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</p> 1954<p>Fundamentally, these APIs are used to do one of the following:</p> 1955<ol> 1956<li>Create a new JavaScript object</li> 1957<li>Convert from a primitive C type to a Node-API value</li> 1958<li>Convert from Node-API value to a primitive C type</li> 1959<li>Get global instances including <code>undefined</code> and <code>null</code></li> 1960</ol> 1961<p>Node-API values are represented by the type <code>napi_value</code>. 1962Any Node-API call that requires a JavaScript value takes in a <code>napi_value</code>. 1963In some cases, the API does check the type of the <code>napi_value</code> up-front. 1964However, for better performance, it's better for the caller to make sure that 1965the <code>napi_value</code> in question is of the JavaScript type expected by the API.</p> 1966<h4>Enum types<span><a class="mark" href="#n_api_enum_types" id="n_api_enum_types">#</a></span></h4> 1967<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> 1968<div class="api_metadata"> 1969<span>Added in: v13.7.0, v10.20.0</span> 1970<span>N-API version: 6</span> 1971</div> 1972<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 1973 napi_key_include_prototypes, 1974 napi_key_own_only 1975} napi_key_collection_mode;</code></pre> 1976<p>Describes the <code>Keys/Properties</code> filter enums:</p> 1977<p><code>napi_key_collection_mode</code> limits the range of collected properties.</p> 1978<p><code>napi_key_own_only</code> limits the collected properties to the given 1979object only. <code>napi_key_include_prototypes</code> will include all keys 1980of the objects's prototype chain as well.</p> 1981<h5>napi_key_filter<span><a class="mark" href="#n_api_napi_key_filter" id="n_api_napi_key_filter">#</a></span></h5> 1982<div class="api_metadata"> 1983<span>Added in: v13.7.0, v10.20.0</span> 1984<span>N-API version: 6</span> 1985</div> 1986<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 1987 napi_key_all_properties = <span class="hljs-number">0</span>, 1988 napi_key_writable = <span class="hljs-number">1</span>, 1989 napi_key_enumerable = <span class="hljs-number">1</span> << <span class="hljs-number">1</span>, 1990 napi_key_configurable = <span class="hljs-number">1</span> << <span class="hljs-number">2</span>, 1991 napi_key_skip_strings = <span class="hljs-number">1</span> << <span class="hljs-number">3</span>, 1992 napi_key_skip_symbols = <span class="hljs-number">1</span> << <span class="hljs-number">4</span> 1993} napi_key_filter;</code></pre> 1994<p>Property filter bits. They can be or'ed to build a composite filter.</p> 1995<h5>napi_key_conversion<span><a class="mark" href="#n_api_napi_key_conversion" id="n_api_napi_key_conversion">#</a></span></h5> 1996<div class="api_metadata"> 1997<span>Added in: v13.7.0, v10.20.0</span> 1998<span>N-API version: 6</span> 1999</div> 2000<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 2001 napi_key_keep_numbers, 2002 napi_key_numbers_to_strings 2003} napi_key_conversion;</code></pre> 2004<p><code>napi_key_numbers_to_strings</code> will convert integer indices to 2005strings. <code>napi_key_keep_numbers</code> will return numbers for integer 2006indices.</p> 2007<h5>napi_valuetype<span><a class="mark" href="#n_api_napi_valuetype" id="n_api_napi_valuetype">#</a></span></h5> 2008<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 2009 <span class="hljs-comment">// ES6 types (corresponds to typeof)</span> 2010 napi_undefined, 2011 napi_null, 2012 napi_boolean, 2013 napi_number, 2014 napi_string, 2015 napi_symbol, 2016 napi_object, 2017 napi_function, 2018 napi_external, 2019 napi_bigint, 2020} napi_valuetype;</code></pre> 2021<p>Describes the type of a <code>napi_value</code>. This generally corresponds to the types 2022described in <a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types">Section 6.1</a> of the ECMAScript Language Specification. 2023In addition to types in that section, <code>napi_valuetype</code> can also represent 2024<code>Function</code>s and <code>Object</code>s with external data.</p> 2025<p>A JavaScript value of type <code>napi_external</code> appears in JavaScript as a plain 2026object such that no properties can be set on it, and no prototype.</p> 2027<h5>napi_typedarray_type<span><a class="mark" href="#n_api_napi_typedarray_type" id="n_api_napi_typedarray_type">#</a></span></h5> 2028<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 2029 napi_int8_array, 2030 napi_uint8_array, 2031 napi_uint8_clamped_array, 2032 napi_int16_array, 2033 napi_uint16_array, 2034 napi_int32_array, 2035 napi_uint32_array, 2036 napi_float32_array, 2037 napi_float64_array, 2038 napi_bigint64_array, 2039 napi_biguint64_array, 2040} napi_typedarray_type;</code></pre> 2041<p>This represents the underlying binary scalar datatype of the <code>TypedArray</code>. 2042Elements of this enum correspond to 2043<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> 2044<h4>Object creation functions<span><a class="mark" href="#n_api_object_creation_functions" id="n_api_object_creation_functions">#</a></span></h4> 2045<h5>napi_create_array<span><a class="mark" href="#n_api_napi_create_array" id="n_api_napi_create_array">#</a></span></h5> 2046<div class="api_metadata"> 2047<span>Added in: v8.0.0</span> 2048<span>N-API version: 1</span> 2049</div> 2050<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> 2051<ul> 2052<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 2053<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Array</code>.</li> 2054</ul> 2055<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2056<p>This API returns a Node-API value corresponding to a JavaScript <code>Array</code> type. 2057JavaScript arrays are described in 2058<a href="https://tc39.github.io/ecma262/#sec-array-objects">Section 22.1</a> of the ECMAScript Language Specification.</p> 2059<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> 2060<div class="api_metadata"> 2061<span>Added in: v8.0.0</span> 2062<span>N-API version: 1</span> 2063</div> 2064<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, 2065 <span class="hljs-type">size_t</span> length, 2066 napi_value* result)</span></code></pre> 2067<ul> 2068<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2069<li><code>[in] length</code>: The initial length of the <code>Array</code>.</li> 2070<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Array</code>.</li> 2071</ul> 2072<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2073<p>This API returns a Node-API value corresponding to a JavaScript <code>Array</code> type. 2074The <code>Array</code>'s length property is set to the passed-in length parameter. 2075However, the underlying buffer is not guaranteed to be pre-allocated by the VM 2076when the array is created. That behavior is left to the underlying VM 2077implementation. If the buffer must be a contiguous block of memory that can be 2078directly read and/or written via C, consider using 2079<a href="#n_api_napi_create_external_arraybuffer"><code>napi_create_external_arraybuffer</code></a>.</p> 2080<p>JavaScript arrays are described in 2081<a href="https://tc39.github.io/ecma262/#sec-array-objects">Section 22.1</a> of the ECMAScript Language Specification.</p> 2082<h5>napi_create_arraybuffer<span><a class="mark" href="#n_api_napi_create_arraybuffer" id="n_api_napi_create_arraybuffer">#</a></span></h5> 2083<div class="api_metadata"> 2084<span>Added in: v8.0.0</span> 2085<span>N-API version: 1</span> 2086</div> 2087<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_arraybuffer</span><span class="hljs-params">(napi_env env, 2088 <span class="hljs-type">size_t</span> byte_length, 2089 <span class="hljs-type">void</span>** data, 2090 napi_value* result)</span></code></pre> 2091<ul> 2092<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2093<li><code>[in] length</code>: The length in bytes of the array buffer to create.</li> 2094<li><code>[out] data</code>: Pointer to the underlying byte buffer of the <code>ArrayBuffer</code>.</li> 2095<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>ArrayBuffer</code>.</li> 2096</ul> 2097<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2098<p>This API returns a Node-API value corresponding to a JavaScript <code>ArrayBuffer</code>. 2099<code>ArrayBuffer</code>s are used to represent fixed-length binary data buffers. They are 2100normally used as a backing-buffer for <code>TypedArray</code> objects. 2101The <code>ArrayBuffer</code> allocated will have an underlying byte buffer whose size is 2102determined by the <code>length</code> parameter that's passed in. 2103The underlying buffer is optionally returned back to the caller in case the 2104caller wants to directly manipulate the buffer. This buffer can only be 2105written to directly from native code. To write to this buffer from JavaScript, 2106a typed array or <code>DataView</code> object would need to be created.</p> 2107<p>JavaScript <code>ArrayBuffer</code> objects are described in 2108<a href="https://tc39.github.io/ecma262/#sec-arraybuffer-objects">Section 24.1</a> of the ECMAScript Language Specification.</p> 2109<h5>napi_create_buffer<span><a class="mark" href="#n_api_napi_create_buffer" id="n_api_napi_create_buffer">#</a></span></h5> 2110<div class="api_metadata"> 2111<span>Added in: v8.0.0</span> 2112<span>N-API version: 1</span> 2113</div> 2114<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_buffer</span><span class="hljs-params">(napi_env env, 2115 <span class="hljs-type">size_t</span> size, 2116 <span class="hljs-type">void</span>** data, 2117 napi_value* result)</span></code></pre> 2118<ul> 2119<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2120<li><code>[in] size</code>: Size in bytes of the underlying buffer.</li> 2121<li><code>[out] data</code>: Raw pointer to the underlying buffer.</li> 2122<li><code>[out] result</code>: A <code>napi_value</code> representing a <code>node::Buffer</code>.</li> 2123</ul> 2124<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2125<p>This API allocates a <code>node::Buffer</code> object. While this is still a 2126fully-supported data structure, in most cases using a <code>TypedArray</code> will suffice.</p> 2127<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> 2128<div class="api_metadata"> 2129<span>Added in: v8.0.0</span> 2130<span>N-API version: 1</span> 2131</div> 2132<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_buffer_copy</span><span class="hljs-params">(napi_env env, 2133 <span class="hljs-type">size_t</span> length, 2134 <span class="hljs-keyword">const</span> <span class="hljs-type">void</span>* data, 2135 <span class="hljs-type">void</span>** result_data, 2136 napi_value* result)</span></code></pre> 2137<ul> 2138<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2139<li><code>[in] size</code>: Size in bytes of the input buffer (should be the same as the size 2140of the new buffer).</li> 2141<li><code>[in] data</code>: Raw pointer to the underlying buffer to copy from.</li> 2142<li><code>[out] result_data</code>: Pointer to the new <code>Buffer</code>'s underlying data buffer.</li> 2143<li><code>[out] result</code>: A <code>napi_value</code> representing a <code>node::Buffer</code>.</li> 2144</ul> 2145<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2146<p>This API allocates a <code>node::Buffer</code> object and initializes it with data copied 2147from the passed-in buffer. While this is still a fully-supported data 2148structure, in most cases using a <code>TypedArray</code> will suffice.</p> 2149<h5>napi_create_date<span><a class="mark" href="#n_api_napi_create_date" id="n_api_napi_create_date">#</a></span></h5> 2150<div class="api_metadata"> 2151<span>Added in: v11.11.0, v10.17.0</span> 2152<span>N-API version: 5</span> 2153</div> 2154<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_date</span><span class="hljs-params">(napi_env env, 2155 <span class="hljs-type">double</span> time, 2156 napi_value* result)</span>;</code></pre> 2157<ul> 2158<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2159<li><code>[in] time</code>: ECMAScript time value in milliseconds since 01 January, 1970 UTC.</li> 2160<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Date</code>.</li> 2161</ul> 2162<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2163<p>This API does not observe leap seconds; they are ignored, as 2164ECMAScript aligns with POSIX time specification.</p> 2165<p>This API allocates a JavaScript <code>Date</code> object.</p> 2166<p>JavaScript <code>Date</code> objects are described in 2167<a href="https://tc39.github.io/ecma262/#sec-date-objects">Section 20.3</a> of the ECMAScript Language Specification.</p> 2168<h5>napi_create_external<span><a class="mark" href="#n_api_napi_create_external" id="n_api_napi_create_external">#</a></span></h5> 2169<div class="api_metadata"> 2170<span>Added in: v8.0.0</span> 2171<span>N-API version: 1</span> 2172</div> 2173<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_external</span><span class="hljs-params">(napi_env env, 2174 <span class="hljs-type">void</span>* data, 2175 napi_finalize finalize_cb, 2176 <span class="hljs-type">void</span>* finalize_hint, 2177 napi_value* result)</span></code></pre> 2178<ul> 2179<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2180<li><code>[in] data</code>: Raw pointer to the external data.</li> 2181<li><code>[in] finalize_cb</code>: Optional callback to call when the external value is being 2182collected. <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 2183<li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 2184collection.</li> 2185<li><code>[out] result</code>: A <code>napi_value</code> representing an external value.</li> 2186</ul> 2187<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2188<p>This API allocates a JavaScript value with external data attached to it. This 2189is used to pass external data through JavaScript code, so it can be retrieved 2190later by native code using <a href="#n_api_napi_get_value_external"><code>napi_get_value_external</code></a>.</p> 2191<p>The API adds a <code>napi_finalize</code> callback which will be called when the JavaScript 2192object just created is ready for garbage collection. It is similar to 2193<code>napi_wrap()</code> except that:</p> 2194<ul> 2195<li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 2196<li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 2197<li>the object created by the API can be used with <code>napi_wrap()</code>.</li> 2198</ul> 2199<p>The created value is not an object, and therefore does not support additional 2200properties. It is considered a distinct value type: calling <code>napi_typeof()</code> with 2201an external value yields <code>napi_external</code>.</p> 2202<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> 2203<div class="api_metadata"> 2204<span>Added in: v8.0.0</span> 2205<span>N-API version: 1</span> 2206</div> 2207<pre><code class="language-c">napi_status 2208<span class="hljs-title function_">napi_create_external_arraybuffer</span><span class="hljs-params">(napi_env env, 2209 <span class="hljs-type">void</span>* external_data, 2210 <span class="hljs-type">size_t</span> byte_length, 2211 napi_finalize finalize_cb, 2212 <span class="hljs-type">void</span>* finalize_hint, 2213 napi_value* result)</span></code></pre> 2214<ul> 2215<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2216<li><code>[in] external_data</code>: Pointer to the underlying byte buffer of the 2217<code>ArrayBuffer</code>.</li> 2218<li><code>[in] byte_length</code>: The length in bytes of the underlying buffer.</li> 2219<li><code>[in] finalize_cb</code>: Optional callback to call when the <code>ArrayBuffer</code> is being 2220collected. <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 2221<li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 2222collection.</li> 2223<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>ArrayBuffer</code>.</li> 2224</ul> 2225<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2226<p><strong>Some runtimes other than Node.js have dropped support for external buffers</strong>. 2227On runtimes other than Node.js this method may return 2228<code>napi_no_external_buffers_allowed</code> to indicate that external 2229buffers are not supported. One such runtime is Electron as 2230described in this issue 2231<a href="https://github.com/electron/electron/issues/35801">electron/issues/35801</a>.</p> 2232<p>In order to maintain broadest compatibility with all runtimes 2233you may define <code>NODE_API_NO_EXTERNAL_BUFFERS_ALLOWED</code> in your addon before 2234includes for the node-api headers. Doing so will hide the 2 functions 2235that create external buffers. This will ensure a compilation error 2236occurs if you accidentally use one of these methods.</p> 2237<p>This API returns a Node-API value corresponding to a JavaScript <code>ArrayBuffer</code>. 2238The underlying byte buffer of the <code>ArrayBuffer</code> is externally allocated and 2239managed. The caller must ensure that the byte buffer remains valid until the 2240finalize callback is called.</p> 2241<p>The API adds a <code>napi_finalize</code> callback which will be called when the JavaScript 2242object just created is ready for garbage collection. It is similar to 2243<code>napi_wrap()</code> except that:</p> 2244<ul> 2245<li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 2246<li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 2247<li>the object created by the API can be used with <code>napi_wrap()</code>.</li> 2248</ul> 2249<p>JavaScript <code>ArrayBuffer</code>s are described in 2250<a href="https://tc39.github.io/ecma262/#sec-arraybuffer-objects">Section 24.1</a> of the ECMAScript Language Specification.</p> 2251<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> 2252<div class="api_metadata"> 2253<span>Added in: v8.0.0</span> 2254<span>N-API version: 1</span> 2255</div> 2256<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_external_buffer</span><span class="hljs-params">(napi_env env, 2257 <span class="hljs-type">size_t</span> length, 2258 <span class="hljs-type">void</span>* data, 2259 napi_finalize finalize_cb, 2260 <span class="hljs-type">void</span>* finalize_hint, 2261 napi_value* result)</span></code></pre> 2262<ul> 2263<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2264<li><code>[in] length</code>: Size in bytes of the input buffer (should be the same as the 2265size of the new buffer).</li> 2266<li><code>[in] data</code>: Raw pointer to the underlying buffer to expose to JavaScript.</li> 2267<li><code>[in] finalize_cb</code>: Optional callback to call when the <code>ArrayBuffer</code> is being 2268collected. <a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 2269<li><code>[in] finalize_hint</code>: Optional hint to pass to the finalize callback during 2270collection.</li> 2271<li><code>[out] result</code>: A <code>napi_value</code> representing a <code>node::Buffer</code>.</li> 2272</ul> 2273<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2274<p><strong>Some runtimes other than Node.js have dropped support for external buffers</strong>. 2275On runtimes other than Node.js this method may return 2276<code>napi_no_external_buffers_allowed</code> to indicate that external 2277buffers are not supported. One such runtime is Electron as 2278described in this issue 2279<a href="https://github.com/electron/electron/issues/35801">electron/issues/35801</a>.</p> 2280<p>In order to maintain broadest compatibility with all runtimes 2281you may define <code>NODE_API_NO_EXTERNAL_BUFFERS_ALLOWED</code> in your addon before 2282includes for the node-api headers. Doing so will hide the 2 functions 2283that create external buffers. This will ensure a compilation error 2284occurs if you accidentally use one of these methods.</p> 2285<p>This API allocates a <code>node::Buffer</code> object and initializes it with data 2286backed by the passed in buffer. While this is still a fully-supported data 2287structure, in most cases using a <code>TypedArray</code> will suffice.</p> 2288<p>The API adds a <code>napi_finalize</code> callback which will be called when the JavaScript 2289object just created is ready for garbage collection. It is similar to 2290<code>napi_wrap()</code> except that:</p> 2291<ul> 2292<li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 2293<li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 2294<li>the object created by the API can be used with <code>napi_wrap()</code>.</li> 2295</ul> 2296<p>For Node.js >=4 <code>Buffers</code> are <code>Uint8Array</code>s.</p> 2297<h5>napi_create_object<span><a class="mark" href="#n_api_napi_create_object" id="n_api_napi_create_object">#</a></span></h5> 2298<div class="api_metadata"> 2299<span>Added in: v8.0.0</span> 2300<span>N-API version: 1</span> 2301</div> 2302<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> 2303<ul> 2304<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2305<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>Object</code>.</li> 2306</ul> 2307<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2308<p>This API allocates a default JavaScript <code>Object</code>. 2309It is the equivalent of doing <code>new Object()</code> in JavaScript.</p> 2310<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 2311ECMAScript Language Specification.</p> 2312<h5>napi_create_symbol<span><a class="mark" href="#n_api_napi_create_symbol" id="n_api_napi_create_symbol">#</a></span></h5> 2313<div class="api_metadata"> 2314<span>Added in: v8.0.0</span> 2315<span>N-API version: 1</span> 2316</div> 2317<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_symbol</span><span class="hljs-params">(napi_env env, 2318 napi_value description, 2319 napi_value* result)</span></code></pre> 2320<ul> 2321<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2322<li><code>[in] description</code>: Optional <code>napi_value</code> which refers to a JavaScript 2323<code>string</code> to be set as the description for the symbol.</li> 2324<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>symbol</code>.</li> 2325</ul> 2326<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2327<p>This API creates a JavaScript <code>symbol</code> value from a UTF8-encoded C string.</p> 2328<p>The JavaScript <code>symbol</code> type is described in <a href="https://tc39.github.io/ecma262/#sec-symbol-objects">Section 19.4</a> 2329of the ECMAScript Language Specification.</p> 2330<h5>napi_create_typedarray<span><a class="mark" href="#n_api_napi_create_typedarray" id="n_api_napi_create_typedarray">#</a></span></h5> 2331<div class="api_metadata"> 2332<span>Added in: v8.0.0</span> 2333<span>N-API version: 1</span> 2334</div> 2335<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_typedarray</span><span class="hljs-params">(napi_env env, 2336 napi_typedarray_type type, 2337 <span class="hljs-type">size_t</span> length, 2338 napi_value arraybuffer, 2339 <span class="hljs-type">size_t</span> byte_offset, 2340 napi_value* result)</span></code></pre> 2341<ul> 2342<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2343<li><code>[in] type</code>: Scalar datatype of the elements within the <code>TypedArray</code>.</li> 2344<li><code>[in] length</code>: Number of elements in the <code>TypedArray</code>.</li> 2345<li><code>[in] arraybuffer</code>: <code>ArrayBuffer</code> underlying the typed array.</li> 2346<li><code>[in] byte_offset</code>: The byte offset within the <code>ArrayBuffer</code> from which to 2347start projecting the <code>TypedArray</code>.</li> 2348<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>TypedArray</code>.</li> 2349</ul> 2350<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2351<p>This API creates a JavaScript <code>TypedArray</code> object over an existing 2352<code>ArrayBuffer</code>. <code>TypedArray</code> objects provide an array-like view over an 2353underlying data buffer where each element has the same underlying binary scalar 2354datatype.</p> 2355<p>It's required that <code>(length * size_of_element) + byte_offset</code> should 2356be <= the size in bytes of the array passed in. If not, a <code>RangeError</code> exception 2357is raised.</p> 2358<p>JavaScript <code>TypedArray</code> objects are described in 2359<a href="https://tc39.github.io/ecma262/#sec-typedarray-objects">Section 22.2</a> of the ECMAScript Language Specification.</p> 2360<h5>napi_create_dataview<span><a class="mark" href="#n_api_napi_create_dataview" id="n_api_napi_create_dataview">#</a></span></h5> 2361<div class="api_metadata"> 2362<span>Added in: v8.3.0</span> 2363<span>N-API version: 1</span> 2364</div> 2365<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_dataview</span><span class="hljs-params">(napi_env env, 2366 <span class="hljs-type">size_t</span> byte_length, 2367 napi_value arraybuffer, 2368 <span class="hljs-type">size_t</span> byte_offset, 2369 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] length</code>: Number of elements in the <code>DataView</code>.</li> 2373<li><code>[in] arraybuffer</code>: <code>ArrayBuffer</code> underlying the <code>DataView</code>.</li> 2374<li><code>[in] byte_offset</code>: The byte offset within the <code>ArrayBuffer</code> from which to 2375start projecting the <code>DataView</code>.</li> 2376<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>DataView</code>.</li> 2377</ul> 2378<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2379<p>This API creates a JavaScript <code>DataView</code> object over an existing <code>ArrayBuffer</code>. 2380<code>DataView</code> objects provide an array-like view over an underlying data buffer, 2381but one which allows items of different size and type in the <code>ArrayBuffer</code>.</p> 2382<p>It is required that <code>byte_length + byte_offset</code> is less than or equal to the 2383size in bytes of the array passed in. If not, a <code>RangeError</code> exception is 2384raised.</p> 2385<p>JavaScript <code>DataView</code> objects are described in 2386<a href="https://tc39.github.io/ecma262/#sec-dataview-objects">Section 24.3</a> of the ECMAScript Language Specification.</p> 2387<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> 2388<h5>napi_create_int32<span><a class="mark" href="#n_api_napi_create_int32" id="n_api_napi_create_int32">#</a></span></h5> 2389<div class="api_metadata"> 2390<span>Added in: v8.4.0</span> 2391<span>N-API version: 1</span> 2392</div> 2393<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> 2394<ul> 2395<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2396<li><code>[in] value</code>: Integer value to be represented in JavaScript.</li> 2397<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2398</ul> 2399<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2400<p>This API is used to convert from the C <code>int32_t</code> type to the JavaScript 2401<code>number</code> type.</p> 2402<p>The JavaScript <code>number</code> type is described in 2403<a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type">Section 6.1.6</a> of the ECMAScript Language Specification.</p> 2404<h5>napi_create_uint32<span><a class="mark" href="#n_api_napi_create_uint32" id="n_api_napi_create_uint32">#</a></span></h5> 2405<div class="api_metadata"> 2406<span>Added in: v8.4.0</span> 2407<span>N-API version: 1</span> 2408</div> 2409<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> 2410<ul> 2411<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2412<li><code>[in] value</code>: Unsigned integer value to be represented in JavaScript.</li> 2413<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2414</ul> 2415<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2416<p>This API is used to convert from the C <code>uint32_t</code> type to the JavaScript 2417<code>number</code> type.</p> 2418<p>The JavaScript <code>number</code> type is described in 2419<a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type">Section 6.1.6</a> of the ECMAScript Language Specification.</p> 2420<h5>napi_create_int64<span><a class="mark" href="#n_api_napi_create_int64" id="n_api_napi_create_int64">#</a></span></h5> 2421<div class="api_metadata"> 2422<span>Added in: v8.4.0</span> 2423<span>N-API version: 1</span> 2424</div> 2425<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> 2426<ul> 2427<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2428<li><code>[in] value</code>: Integer value to be represented in JavaScript.</li> 2429<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2430</ul> 2431<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2432<p>This API is used to convert from the C <code>int64_t</code> type to the JavaScript 2433<code>number</code> type.</p> 2434<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> 2435of the ECMAScript Language Specification. Note the complete range of <code>int64_t</code> 2436cannot be represented with full precision in JavaScript. Integer values 2437outside 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> - 2438<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> 2439<h5>napi_create_double<span><a class="mark" href="#n_api_napi_create_double" id="n_api_napi_create_double">#</a></span></h5> 2440<div class="api_metadata"> 2441<span>Added in: v8.4.0</span> 2442<span>N-API version: 1</span> 2443</div> 2444<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> 2445<ul> 2446<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2447<li><code>[in] value</code>: Double-precision value to be represented in JavaScript.</li> 2448<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>number</code>.</li> 2449</ul> 2450<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2451<p>This API is used to convert from the C <code>double</code> type to the JavaScript 2452<code>number</code> type.</p> 2453<p>The JavaScript <code>number</code> type is described in 2454<a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type">Section 6.1.6</a> of the ECMAScript Language Specification.</p> 2455<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> 2456<div class="api_metadata"> 2457<span>Added in: v10.7.0</span> 2458<span>N-API version: 6</span> 2459</div> 2460<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_bigint_int64</span><span class="hljs-params">(napi_env env, 2461 <span class="hljs-type">int64_t</span> value, 2462 napi_value* result)</span>;</code></pre> 2463<ul> 2464<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2465<li><code>[in] value</code>: Integer value to be represented in JavaScript.</li> 2466<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>BigInt</code>.</li> 2467</ul> 2468<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2469<p>This API converts the C <code>int64_t</code> type to the JavaScript <code>BigInt</code> type.</p> 2470<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> 2471<div class="api_metadata"> 2472<span>Added in: v10.7.0</span> 2473<span>N-API version: 6</span> 2474</div> 2475<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_bigint_uint64</span><span class="hljs-params">(napi_env env, 2476 <span class="hljs-type">uint64_t</span> value, 2477 napi_value* result)</span>;</code></pre> 2478<ul> 2479<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2480<li><code>[in] value</code>: Unsigned integer value to be represented in JavaScript.</li> 2481<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>BigInt</code>.</li> 2482</ul> 2483<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2484<p>This API converts the C <code>uint64_t</code> type to the JavaScript <code>BigInt</code> type.</p> 2485<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> 2486<div class="api_metadata"> 2487<span>Added in: v10.7.0</span> 2488<span>N-API version: 6</span> 2489</div> 2490<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_bigint_words</span><span class="hljs-params">(napi_env env, 2491 <span class="hljs-type">int</span> sign_bit, 2492 <span class="hljs-type">size_t</span> word_count, 2493 <span class="hljs-keyword">const</span> <span class="hljs-type">uint64_t</span>* words, 2494 napi_value* result)</span>;</code></pre> 2495<ul> 2496<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2497<li><code>[in] sign_bit</code>: Determines if the resulting <code>BigInt</code> will be positive or 2498negative.</li> 2499<li><code>[in] word_count</code>: The length of the <code>words</code> array.</li> 2500<li><code>[in] words</code>: An array of <code>uint64_t</code> little-endian 64-bit words.</li> 2501<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>BigInt</code>.</li> 2502</ul> 2503<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2504<p>This API converts an array of unsigned 64-bit words into a single <code>BigInt</code> 2505value.</p> 2506<p>The resulting <code>BigInt</code> is calculated as: (–1)<sup><code>sign_bit</code></sup> (<code>words[0]</code> 2507× (2<sup>64</sup>)<sup>0</sup> + <code>words[1]</code> × (2<sup>64</sup>)<sup>1</sup> + …)</p> 2508<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> 2509<div class="api_metadata"> 2510<span>Added in: v8.0.0</span> 2511<span>N-API version: 1</span> 2512</div> 2513<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_string_latin1</span><span class="hljs-params">(napi_env env, 2514 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* str, 2515 <span class="hljs-type">size_t</span> length, 2516 napi_value* result)</span>;</code></pre> 2517<ul> 2518<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2519<li><code>[in] str</code>: Character buffer representing an ISO-8859-1-encoded string.</li> 2520<li><code>[in] length</code>: The length of the string in bytes, or <code>NAPI_AUTO_LENGTH</code> if it 2521is null-terminated.</li> 2522<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>string</code>.</li> 2523</ul> 2524<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2525<p>This API creates a JavaScript <code>string</code> value from an ISO-8859-1-encoded C 2526string. The native string is copied.</p> 2527<p>The JavaScript <code>string</code> type is described in 2528<a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type">Section 6.1.4</a> of the ECMAScript Language Specification.</p> 2529<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> 2530<div class="api_metadata"> 2531<span>Added in: v8.0.0</span> 2532<span>N-API version: 1</span> 2533</div> 2534<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_string_utf16</span><span class="hljs-params">(napi_env env, 2535 <span class="hljs-keyword">const</span> <span class="hljs-type">char16_t</span>* str, 2536 <span class="hljs-type">size_t</span> length, 2537 napi_value* result)</span></code></pre> 2538<ul> 2539<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2540<li><code>[in] str</code>: Character buffer representing a UTF16-LE-encoded string.</li> 2541<li><code>[in] length</code>: The length of the string in two-byte code units, or 2542<code>NAPI_AUTO_LENGTH</code> if it is null-terminated.</li> 2543<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>string</code>.</li> 2544</ul> 2545<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2546<p>This API creates a JavaScript <code>string</code> value from a UTF16-LE-encoded C string. 2547The native string is copied.</p> 2548<p>The JavaScript <code>string</code> type is described in 2549<a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type">Section 6.1.4</a> of the ECMAScript Language Specification.</p> 2550<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> 2551<div class="api_metadata"> 2552<span>Added in: v8.0.0</span> 2553<span>N-API version: 1</span> 2554</div> 2555<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_string_utf8</span><span class="hljs-params">(napi_env env, 2556 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* str, 2557 <span class="hljs-type">size_t</span> length, 2558 napi_value* result)</span></code></pre> 2559<ul> 2560<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2561<li><code>[in] str</code>: Character buffer representing a UTF8-encoded string.</li> 2562<li><code>[in] length</code>: The length of the string in bytes, or <code>NAPI_AUTO_LENGTH</code> if it 2563is null-terminated.</li> 2564<li><code>[out] result</code>: A <code>napi_value</code> representing a JavaScript <code>string</code>.</li> 2565</ul> 2566<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2567<p>This API creates a JavaScript <code>string</code> value from a UTF8-encoded C string. 2568The native string is copied.</p> 2569<p>The JavaScript <code>string</code> type is described in 2570<a href="https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type">Section 6.1.4</a> of the ECMAScript Language Specification.</p> 2571<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> 2572<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> 2573<div class="api_metadata"> 2574<span>Added in: v8.0.0</span> 2575<span>N-API version: 1</span> 2576</div> 2577<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_array_length</span><span class="hljs-params">(napi_env env, 2578 napi_value value, 2579 <span class="hljs-type">uint32_t</span>* result)</span></code></pre> 2580<ul> 2581<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2582<li><code>[in] value</code>: <code>napi_value</code> representing the JavaScript <code>Array</code> whose length is 2583being queried.</li> 2584<li><code>[out] result</code>: <code>uint32</code> representing length of the array.</li> 2585</ul> 2586<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2587<p>This API returns the length of an array.</p> 2588<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 2589Specification.</p> 2590<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> 2591<div class="api_metadata"> 2592<span>Added in: v8.0.0</span> 2593<span>N-API version: 1</span> 2594</div> 2595<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_arraybuffer_info</span><span class="hljs-params">(napi_env env, 2596 napi_value arraybuffer, 2597 <span class="hljs-type">void</span>** data, 2598 <span class="hljs-type">size_t</span>* byte_length)</span></code></pre> 2599<ul> 2600<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2601<li><code>[in] arraybuffer</code>: <code>napi_value</code> representing the <code>ArrayBuffer</code> being queried.</li> 2602<li><code>[out] data</code>: The underlying data buffer of the <code>ArrayBuffer</code>. If byte_length 2603is <code>0</code>, this may be <code>NULL</code> or any other pointer value.</li> 2604<li><code>[out] byte_length</code>: Length in bytes of the underlying data buffer.</li> 2605</ul> 2606<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2607<p>This API is used to retrieve the underlying data buffer of an <code>ArrayBuffer</code> and 2608its length.</p> 2609<p><em>WARNING</em>: Use caution while using this API. The lifetime of the underlying data 2610buffer is managed by the <code>ArrayBuffer</code> even after it's returned. A 2611possible safe way to use this API is in conjunction with 2612<a href="#n_api_napi_create_reference"><code>napi_create_reference</code></a>, which can be used to guarantee control over the 2613lifetime of the <code>ArrayBuffer</code>. It's also safe to use the returned data buffer 2614within the same callback as long as there are no calls to other APIs that might 2615trigger a GC.</p> 2616<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> 2617<div class="api_metadata"> 2618<span>Added in: v8.0.0</span> 2619<span>N-API version: 1</span> 2620</div> 2621<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_buffer_info</span><span class="hljs-params">(napi_env env, 2622 napi_value value, 2623 <span class="hljs-type">void</span>** data, 2624 <span class="hljs-type">size_t</span>* length)</span></code></pre> 2625<ul> 2626<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2627<li><code>[in] value</code>: <code>napi_value</code> representing the <code>node::Buffer</code> being queried.</li> 2628<li><code>[out] data</code>: The underlying data buffer of the <code>node::Buffer</code>. 2629If length is <code>0</code>, this may be <code>NULL</code> or any other pointer value.</li> 2630<li><code>[out] length</code>: Length in bytes of the underlying data buffer.</li> 2631</ul> 2632<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2633<p>This API is used to retrieve the underlying data buffer of a <code>node::Buffer</code> 2634and it's length.</p> 2635<p><em>Warning</em>: Use caution while using this API since the underlying data buffer's 2636lifetime is not guaranteed if it's managed by the VM.</p> 2637<h5>napi_get_prototype<span><a class="mark" href="#n_api_napi_get_prototype" id="n_api_napi_get_prototype">#</a></span></h5> 2638<div class="api_metadata"> 2639<span>Added in: v8.0.0</span> 2640<span>N-API version: 1</span> 2641</div> 2642<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_prototype</span><span class="hljs-params">(napi_env env, 2643 napi_value object, 2644 napi_value* result)</span></code></pre> 2645<ul> 2646<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2647<li><code>[in] object</code>: <code>napi_value</code> representing JavaScript <code>Object</code> whose prototype 2648to return. This returns the equivalent of <code>Object.getPrototypeOf</code> (which is 2649not the same as the function's <code>prototype</code> property).</li> 2650<li><code>[out] result</code>: <code>napi_value</code> representing prototype of the given object.</li> 2651</ul> 2652<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2653<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> 2654<div class="api_metadata"> 2655<span>Added in: v8.0.0</span> 2656<span>N-API version: 1</span> 2657</div> 2658<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_typedarray_info</span><span class="hljs-params">(napi_env env, 2659 napi_value typedarray, 2660 napi_typedarray_type* type, 2661 <span class="hljs-type">size_t</span>* length, 2662 <span class="hljs-type">void</span>** data, 2663 napi_value* arraybuffer, 2664 <span class="hljs-type">size_t</span>* byte_offset)</span></code></pre> 2665<ul> 2666<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2667<li><code>[in] typedarray</code>: <code>napi_value</code> representing the <code>TypedArray</code> whose 2668properties to query.</li> 2669<li><code>[out] type</code>: Scalar datatype of the elements within the <code>TypedArray</code>.</li> 2670<li><code>[out] length</code>: The number of elements in the <code>TypedArray</code>.</li> 2671<li><code>[out] data</code>: The data buffer underlying the <code>TypedArray</code> adjusted by 2672the <code>byte_offset</code> value so that it points to the first element in the 2673<code>TypedArray</code>. If the length of the array is <code>0</code>, this may be <code>NULL</code> or 2674any other pointer value.</li> 2675<li><code>[out] arraybuffer</code>: The <code>ArrayBuffer</code> underlying the <code>TypedArray</code>.</li> 2676<li><code>[out] byte_offset</code>: The byte offset within the underlying native array 2677at which the first element of the arrays is located. The value for the data 2678parameter has already been adjusted so that data points to the first element 2679in the array. Therefore, the first byte of the native array would be at 2680<code>data - byte_offset</code>.</li> 2681</ul> 2682<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2683<p>This API returns various properties of a typed array.</p> 2684<p><em>Warning</em>: Use caution while using this API since the underlying data buffer 2685is managed by the VM.</p> 2686<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> 2687<div class="api_metadata"> 2688<span>Added in: v8.3.0</span> 2689<span>N-API version: 1</span> 2690</div> 2691<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_dataview_info</span><span class="hljs-params">(napi_env env, 2692 napi_value dataview, 2693 <span class="hljs-type">size_t</span>* byte_length, 2694 <span class="hljs-type">void</span>** data, 2695 napi_value* arraybuffer, 2696 <span class="hljs-type">size_t</span>* byte_offset)</span></code></pre> 2697<ul> 2698<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2699<li><code>[in] dataview</code>: <code>napi_value</code> representing the <code>DataView</code> whose 2700properties to query.</li> 2701<li><code>[out] byte_length</code>: Number of bytes in the <code>DataView</code>.</li> 2702<li><code>[out] data</code>: The data buffer underlying the <code>DataView</code>. 2703If byte_length is <code>0</code>, this may be <code>NULL</code> or any other pointer value.</li> 2704<li><code>[out] arraybuffer</code>: <code>ArrayBuffer</code> underlying the <code>DataView</code>.</li> 2705<li><code>[out] byte_offset</code>: The byte offset within the data buffer from which 2706to start projecting the <code>DataView</code>.</li> 2707</ul> 2708<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2709<p>This API returns various properties of a <code>DataView</code>.</p> 2710<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> 2711<div class="api_metadata"> 2712<span>Added in: v11.11.0, v10.17.0</span> 2713<span>N-API version: 5</span> 2714</div> 2715<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_date_value</span><span class="hljs-params">(napi_env env, 2716 napi_value value, 2717 <span class="hljs-type">double</span>* result)</span></code></pre> 2718<ul> 2719<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2720<li><code>[in] value</code>: <code>napi_value</code> representing a JavaScript <code>Date</code>.</li> 2721<li><code>[out] result</code>: Time value as a <code>double</code> represented as milliseconds since 2722midnight at the beginning of 01 January, 1970 UTC.</li> 2723</ul> 2724<p>This API does not observe leap seconds; they are ignored, as 2725ECMAScript aligns with POSIX time specification.</p> 2726<p>Returns <code>napi_ok</code> if the API succeeded. If a non-date <code>napi_value</code> is passed 2727in it returns <code>napi_date_expected</code>.</p> 2728<p>This API returns the C double primitive of time value for the given JavaScript 2729<code>Date</code>.</p> 2730<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> 2731<div class="api_metadata"> 2732<span>Added in: v8.0.0</span> 2733<span>N-API version: 1</span> 2734</div> 2735<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> 2736<ul> 2737<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2738<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>Boolean</code>.</li> 2739<li><code>[out] result</code>: C boolean primitive equivalent of the given JavaScript 2740<code>Boolean</code>.</li> 2741</ul> 2742<p>Returns <code>napi_ok</code> if the API succeeded. If a non-boolean <code>napi_value</code> is 2743passed in it returns <code>napi_boolean_expected</code>.</p> 2744<p>This API returns the C boolean primitive equivalent of the given JavaScript 2745<code>Boolean</code>.</p> 2746<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> 2747<div class="api_metadata"> 2748<span>Added in: v8.0.0</span> 2749<span>N-API version: 1</span> 2750</div> 2751<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_double</span><span class="hljs-params">(napi_env env, 2752 napi_value value, 2753 <span class="hljs-type">double</span>* result)</span></code></pre> 2754<ul> 2755<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2756<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2757<li><code>[out] result</code>: C double primitive equivalent of the given JavaScript 2758<code>number</code>.</li> 2759</ul> 2760<p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> is passed 2761in it returns <code>napi_number_expected</code>.</p> 2762<p>This API returns the C double primitive equivalent of the given JavaScript 2763<code>number</code>.</p> 2764<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> 2765<div class="api_metadata"> 2766<span>Added in: v10.7.0</span> 2767<span>N-API version: 6</span> 2768</div> 2769<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, 2770 napi_value value, 2771 <span class="hljs-type">int64_t</span>* result, 2772 <span class="hljs-type">bool</span>* lossless)</span>;</code></pre> 2773<ul> 2774<li><code>[in] env</code>: The environment that the API is invoked under</li> 2775<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>BigInt</code>.</li> 2776<li><code>[out] result</code>: C <code>int64_t</code> primitive equivalent of the given JavaScript 2777<code>BigInt</code>.</li> 2778<li><code>[out] lossless</code>: Indicates whether the <code>BigInt</code> value was converted 2779losslessly.</li> 2780</ul> 2781<p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>BigInt</code> is passed in it 2782returns <code>napi_bigint_expected</code>.</p> 2783<p>This API returns the C <code>int64_t</code> primitive equivalent of the given JavaScript 2784<code>BigInt</code>. If needed it will truncate the value, setting <code>lossless</code> to <code>false</code>.</p> 2785<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> 2786<div class="api_metadata"> 2787<span>Added in: v10.7.0</span> 2788<span>N-API version: 6</span> 2789</div> 2790<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, 2791 napi_value value, 2792 <span class="hljs-type">uint64_t</span>* result, 2793 <span class="hljs-type">bool</span>* lossless)</span>;</code></pre> 2794<ul> 2795<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2796<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>BigInt</code>.</li> 2797<li><code>[out] result</code>: C <code>uint64_t</code> primitive equivalent of the given JavaScript 2798<code>BigInt</code>.</li> 2799<li><code>[out] lossless</code>: Indicates whether the <code>BigInt</code> value was converted 2800losslessly.</li> 2801</ul> 2802<p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>BigInt</code> is passed in it 2803returns <code>napi_bigint_expected</code>.</p> 2804<p>This API returns the C <code>uint64_t</code> primitive equivalent of the given JavaScript 2805<code>BigInt</code>. If needed it will truncate the value, setting <code>lossless</code> to <code>false</code>.</p> 2806<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> 2807<div class="api_metadata"> 2808<span>Added in: v10.7.0</span> 2809<span>N-API version: 6</span> 2810</div> 2811<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, 2812 napi_value value, 2813 <span class="hljs-type">int</span>* sign_bit, 2814 <span class="hljs-type">size_t</span>* word_count, 2815 <span class="hljs-type">uint64_t</span>* words)</span>;</code></pre> 2816<ul> 2817<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2818<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>BigInt</code>.</li> 2819<li><code>[out] sign_bit</code>: Integer representing if the JavaScript <code>BigInt</code> is positive 2820or negative.</li> 2821<li><code>[in/out] word_count</code>: Must be initialized to the length of the <code>words</code> 2822array. Upon return, it will be set to the actual number of words that 2823would be needed to store this <code>BigInt</code>.</li> 2824<li><code>[out] words</code>: Pointer to a pre-allocated 64-bit word array.</li> 2825</ul> 2826<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2827<p>This API converts a single <code>BigInt</code> value into a sign bit, 64-bit little-endian 2828array, and the number of elements in the array. <code>sign_bit</code> and <code>words</code> may be 2829both set to <code>NULL</code>, in order to get only <code>word_count</code>.</p> 2830<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> 2831<div class="api_metadata"> 2832<span>Added in: v8.0.0</span> 2833<span>N-API version: 1</span> 2834</div> 2835<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_external</span><span class="hljs-params">(napi_env env, 2836 napi_value value, 2837 <span class="hljs-type">void</span>** result)</span></code></pre> 2838<ul> 2839<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2840<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript external value.</li> 2841<li><code>[out] result</code>: Pointer to the data wrapped by the JavaScript external value.</li> 2842</ul> 2843<p>Returns <code>napi_ok</code> if the API succeeded. If a non-external <code>napi_value</code> is 2844passed in it returns <code>napi_invalid_arg</code>.</p> 2845<p>This API retrieves the external data pointer that was previously passed to 2846<code>napi_create_external()</code>.</p> 2847<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> 2848<div class="api_metadata"> 2849<span>Added in: v8.0.0</span> 2850<span>N-API version: 1</span> 2851</div> 2852<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_int32</span><span class="hljs-params">(napi_env env, 2853 napi_value value, 2854 <span class="hljs-type">int32_t</span>* result)</span></code></pre> 2855<ul> 2856<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2857<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2858<li><code>[out] result</code>: C <code>int32</code> primitive equivalent of the given JavaScript 2859<code>number</code>.</li> 2860</ul> 2861<p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> 2862is passed in <code>napi_number_expected</code>.</p> 2863<p>This API returns the C <code>int32</code> primitive equivalent 2864of the given JavaScript <code>number</code>.</p> 2865<p>If the number exceeds the range of the 32 bit integer, then the result is 2866truncated to the equivalent of the bottom 32 bits. This can result in a large 2867positive number becoming a negative number if the value is > 2<sup>31</sup> - 1.</p> 2868<p>Non-finite number values (<code>NaN</code>, <code>+Infinity</code>, or <code>-Infinity</code>) set the 2869result to zero.</p> 2870<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> 2871<div class="api_metadata"> 2872<span>Added in: v8.0.0</span> 2873<span>N-API version: 1</span> 2874</div> 2875<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_int64</span><span class="hljs-params">(napi_env env, 2876 napi_value value, 2877 <span class="hljs-type">int64_t</span>* result)</span></code></pre> 2878<ul> 2879<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2880<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2881<li><code>[out] result</code>: C <code>int64</code> primitive equivalent of the given JavaScript 2882<code>number</code>.</li> 2883</ul> 2884<p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> 2885is passed in it returns <code>napi_number_expected</code>.</p> 2886<p>This API returns the C <code>int64</code> primitive equivalent of the given JavaScript 2887<code>number</code>.</p> 2888<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> 2889<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 2890precision.</p> 2891<p>Non-finite number values (<code>NaN</code>, <code>+Infinity</code>, or <code>-Infinity</code>) set the 2892result to zero.</p> 2893<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> 2894<div class="api_metadata"> 2895<span>Added in: v8.0.0</span> 2896<span>N-API version: 1</span> 2897</div> 2898<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, 2899 napi_value value, 2900 <span class="hljs-type">char</span>* buf, 2901 <span class="hljs-type">size_t</span> bufsize, 2902 <span class="hljs-type">size_t</span>* result)</span></code></pre> 2903<ul> 2904<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2905<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript string.</li> 2906<li><code>[in] buf</code>: Buffer to write the ISO-8859-1-encoded string into. If <code>NULL</code> is 2907passed in, the length of the string in bytes and excluding the null terminator 2908is returned in <code>result</code>.</li> 2909<li><code>[in] bufsize</code>: Size of the destination buffer. When this value is 2910insufficient, the returned string is truncated and null-terminated.</li> 2911<li><code>[out] result</code>: Number of bytes copied into the buffer, excluding the null 2912terminator.</li> 2913</ul> 2914<p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>string</code> <code>napi_value</code> 2915is passed in it returns <code>napi_string_expected</code>.</p> 2916<p>This API returns the ISO-8859-1-encoded string corresponding the value passed 2917in.</p> 2918<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> 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_utf8</span><span class="hljs-params">(napi_env env, 2924 napi_value value, 2925 <span class="hljs-type">char</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 UTF8-encoded string into. If <code>NULL</code> is passed 2932in, the length of the string in bytes and excluding the null terminator is 2933returned in <code>result</code>.</li> 2934<li><code>[in] bufsize</code>: Size of the destination buffer. When this value is 2935insufficient, the returned string is truncated and null-terminated.</li> 2936<li><code>[out] result</code>: Number of bytes copied into the buffer, excluding the null 2937terminator.</li> 2938</ul> 2939<p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>string</code> <code>napi_value</code> 2940is passed in it returns <code>napi_string_expected</code>.</p> 2941<p>This API returns the UTF8-encoded string corresponding the value passed in.</p> 2942<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> 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_string_utf16</span><span class="hljs-params">(napi_env env, 2948 napi_value value, 2949 <span class="hljs-type">char16_t</span>* buf, 2950 <span class="hljs-type">size_t</span> bufsize, 2951 <span class="hljs-type">size_t</span>* result)</span></code></pre> 2952<ul> 2953<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2954<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript string.</li> 2955<li><code>[in] buf</code>: Buffer to write the UTF16-LE-encoded string into. If <code>NULL</code> is 2956passed in, the length of the string in 2-byte code units and excluding the 2957null terminator is returned.</li> 2958<li><code>[in] bufsize</code>: Size of the destination buffer. When this value is 2959insufficient, the returned string is truncated and null-terminated.</li> 2960<li><code>[out] result</code>: Number of 2-byte code units copied into the buffer, excluding 2961the null terminator.</li> 2962</ul> 2963<p>Returns <code>napi_ok</code> if the API succeeded. If a non-<code>string</code> <code>napi_value</code> 2964is passed in it returns <code>napi_string_expected</code>.</p> 2965<p>This API returns the UTF16-encoded string corresponding the value passed in.</p> 2966<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> 2967<div class="api_metadata"> 2968<span>Added in: v8.0.0</span> 2969<span>N-API version: 1</span> 2970</div> 2971<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_value_uint32</span><span class="hljs-params">(napi_env env, 2972 napi_value value, 2973 <span class="hljs-type">uint32_t</span>* result)</span></code></pre> 2974<ul> 2975<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2976<li><code>[in] value</code>: <code>napi_value</code> representing JavaScript <code>number</code>.</li> 2977<li><code>[out] result</code>: C primitive equivalent of the given <code>napi_value</code> as a 2978<code>uint32_t</code>.</li> 2979</ul> 2980<p>Returns <code>napi_ok</code> if the API succeeded. If a non-number <code>napi_value</code> 2981is passed in it returns <code>napi_number_expected</code>.</p> 2982<p>This API returns the C primitive equivalent of the given <code>napi_value</code> as a 2983<code>uint32_t</code>.</p> 2984<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> 2985<h5>napi_get_boolean<span><a class="mark" href="#n_api_napi_get_boolean" id="n_api_napi_get_boolean">#</a></span></h5> 2986<div class="api_metadata"> 2987<span>Added in: v8.0.0</span> 2988<span>N-API version: 1</span> 2989</div> 2990<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> 2991<ul> 2992<li><code>[in] env</code>: The environment that the API is invoked under.</li> 2993<li><code>[in] value</code>: The value of the boolean to retrieve.</li> 2994<li><code>[out] result</code>: <code>napi_value</code> representing JavaScript <code>Boolean</code> singleton to 2995retrieve.</li> 2996</ul> 2997<p>Returns <code>napi_ok</code> if the API succeeded.</p> 2998<p>This API is used to return the JavaScript singleton object that is used to 2999represent the given boolean value.</p> 3000<h5>napi_get_global<span><a class="mark" href="#n_api_napi_get_global" id="n_api_napi_get_global">#</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_global</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 <code>global</code> object.</li> 3009</ul> 3010<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3011<p>This API returns the <code>global</code> object.</p> 3012<h5>napi_get_null<span><a class="mark" href="#n_api_napi_get_null" id="n_api_napi_get_null">#</a></span></h5> 3013<div class="api_metadata"> 3014<span>Added in: v8.0.0</span> 3015<span>N-API version: 1</span> 3016</div> 3017<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> 3018<ul> 3019<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3020<li><code>[out] result</code>: <code>napi_value</code> representing JavaScript <code>null</code> object.</li> 3021</ul> 3022<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3023<p>This API returns the <code>null</code> object.</p> 3024<h5>napi_get_undefined<span><a class="mark" href="#n_api_napi_get_undefined" id="n_api_napi_get_undefined">#</a></span></h5> 3025<div class="api_metadata"> 3026<span>Added in: v8.0.0</span> 3027<span>N-API version: 1</span> 3028</div> 3029<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> 3030<ul> 3031<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3032<li><code>[out] result</code>: <code>napi_value</code> representing JavaScript Undefined value.</li> 3033</ul> 3034<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3035<p>This API returns the Undefined object.</p> 3036</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> 3037<p>Node-API exposes a set of APIs to perform some abstract operations on JavaScript 3038values. Some of these operations are documented under <a href="https://tc39.github.io/ecma262/#sec-abstract-operations">Section 7</a> 3039of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</p> 3040<p>These APIs support doing one of the following:</p> 3041<ol> 3042<li>Coerce JavaScript values to specific JavaScript types (such as <code>number</code> or 3043<code>string</code>).</li> 3044<li>Check the type of a JavaScript value.</li> 3045<li>Check for equality between two JavaScript values.</li> 3046</ol> 3047<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> 3048<div class="api_metadata"> 3049<span>Added in: v8.0.0</span> 3050<span>N-API version: 1</span> 3051</div> 3052<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_bool</span><span class="hljs-params">(napi_env env, 3053 napi_value value, 3054 napi_value* result)</span></code></pre> 3055<ul> 3056<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3057<li><code>[in] value</code>: The JavaScript value to coerce.</li> 3058<li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>Boolean</code>.</li> 3059</ul> 3060<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3061<p>This API implements the abstract operation <code>ToBoolean()</code> as defined in 3062<a href="https://tc39.github.io/ecma262/#sec-toboolean">Section 7.1.2</a> of the ECMAScript Language Specification. 3063This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3064<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> 3065<div class="api_metadata"> 3066<span>Added in: v8.0.0</span> 3067<span>N-API version: 1</span> 3068</div> 3069<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_number</span><span class="hljs-params">(napi_env env, 3070 napi_value value, 3071 napi_value* result)</span></code></pre> 3072<ul> 3073<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3074<li><code>[in] value</code>: The JavaScript value to coerce.</li> 3075<li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>number</code>.</li> 3076</ul> 3077<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3078<p>This API implements the abstract operation <code>ToNumber()</code> as defined in 3079<a href="https://tc39.github.io/ecma262/#sec-tonumber">Section 7.1.3</a> of the ECMAScript Language Specification. 3080This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3081<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> 3082<div class="api_metadata"> 3083<span>Added in: v8.0.0</span> 3084<span>N-API version: 1</span> 3085</div> 3086<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_object</span><span class="hljs-params">(napi_env env, 3087 napi_value value, 3088 napi_value* result)</span></code></pre> 3089<ul> 3090<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3091<li><code>[in] value</code>: The JavaScript value to coerce.</li> 3092<li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>Object</code>.</li> 3093</ul> 3094<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3095<p>This API implements the abstract operation <code>ToObject()</code> as defined in 3096<a href="https://tc39.github.io/ecma262/#sec-toobject">Section 7.1.13</a> of the ECMAScript Language Specification. 3097This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3098<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> 3099<div class="api_metadata"> 3100<span>Added in: v8.0.0</span> 3101<span>N-API version: 1</span> 3102</div> 3103<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_coerce_to_string</span><span class="hljs-params">(napi_env env, 3104 napi_value value, 3105 napi_value* result)</span></code></pre> 3106<ul> 3107<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3108<li><code>[in] value</code>: The JavaScript value to coerce.</li> 3109<li><code>[out] result</code>: <code>napi_value</code> representing the coerced JavaScript <code>string</code>.</li> 3110</ul> 3111<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3112<p>This API implements the abstract operation <code>ToString()</code> as defined in 3113<a href="https://tc39.github.io/ecma262/#sec-toobject">Section 7.1.13</a> of the ECMAScript Language Specification. 3114This API can be re-entrant if getters are defined on the passed-in <code>Object</code>.</p> 3115<h4>napi_typeof<span><a class="mark" href="#n_api_napi_typeof" id="n_api_napi_typeof">#</a></span></h4> 3116<div class="api_metadata"> 3117<span>Added in: v8.0.0</span> 3118<span>N-API version: 1</span> 3119</div> 3120<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> 3121<ul> 3122<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3123<li><code>[in] value</code>: The JavaScript value whose type to query.</li> 3124<li><code>[out] result</code>: The type of the JavaScript value.</li> 3125</ul> 3126<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3127<ul> 3128<li><code>napi_invalid_arg</code> if the type of <code>value</code> is not a known ECMAScript type and 3129<code>value</code> is not an External value.</li> 3130</ul> 3131<p>This API represents behavior similar to invoking the <code>typeof</code> Operator on 3132the object as defined in <a href="https://tc39.github.io/ecma262/#sec-typeof-operator">Section 12.5.5</a> of the ECMAScript Language 3133Specification. However, there are some differences:</p> 3134<ol> 3135<li>It has support for detecting an External value.</li> 3136<li>It detects <code>null</code> as a separate type, while ECMAScript <code>typeof</code> would detect 3137<code>object</code>.</li> 3138</ol> 3139<p>If <code>value</code> has a type that is invalid, an error is returned.</p> 3140<h4>napi_instanceof<span><a class="mark" href="#n_api_napi_instanceof" id="n_api_napi_instanceof">#</a></span></h4> 3141<div class="api_metadata"> 3142<span>Added in: v8.0.0</span> 3143<span>N-API version: 1</span> 3144</div> 3145<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_instanceof</span><span class="hljs-params">(napi_env env, 3146 napi_value object, 3147 napi_value constructor, 3148 <span class="hljs-type">bool</span>* result)</span></code></pre> 3149<ul> 3150<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3151<li><code>[in] object</code>: The JavaScript value to check.</li> 3152<li><code>[in] constructor</code>: The JavaScript function object of the constructor function 3153to check against.</li> 3154<li><code>[out] result</code>: Boolean that is set to true if <code>object instanceof constructor</code> 3155is true.</li> 3156</ul> 3157<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3158<p>This API represents invoking the <code>instanceof</code> Operator on the object as 3159defined in <a href="https://tc39.github.io/ecma262/#sec-instanceofoperator">Section 12.10.4</a> of the ECMAScript Language Specification.</p> 3160<h4>napi_is_array<span><a class="mark" href="#n_api_napi_is_array" id="n_api_napi_is_array">#</a></span></h4> 3161<div class="api_metadata"> 3162<span>Added in: v8.0.0</span> 3163<span>N-API version: 1</span> 3164</div> 3165<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> 3166<ul> 3167<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3168<li><code>[in] value</code>: The JavaScript value to check.</li> 3169<li><code>[out] result</code>: Whether the given object is an array.</li> 3170</ul> 3171<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3172<p>This API represents invoking the <code>IsArray</code> operation on the object 3173as defined in <a href="https://tc39.github.io/ecma262/#sec-isarray">Section 7.2.2</a> of the ECMAScript Language Specification.</p> 3174<h4>napi_is_arraybuffer<span><a class="mark" href="#n_api_napi_is_arraybuffer" id="n_api_napi_is_arraybuffer">#</a></span></h4> 3175<div class="api_metadata"> 3176<span>Added in: v8.0.0</span> 3177<span>N-API version: 1</span> 3178</div> 3179<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> 3180<ul> 3181<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3182<li><code>[in] value</code>: The JavaScript value to check.</li> 3183<li><code>[out] result</code>: Whether the given object is an <code>ArrayBuffer</code>.</li> 3184</ul> 3185<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3186<p>This API checks if the <code>Object</code> passed in is an array buffer.</p> 3187<h4>napi_is_buffer<span><a class="mark" href="#n_api_napi_is_buffer" id="n_api_napi_is_buffer">#</a></span></h4> 3188<div class="api_metadata"> 3189<span>Added in: v8.0.0</span> 3190<span>N-API version: 1</span> 3191</div> 3192<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> 3193<ul> 3194<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3195<li><code>[in] value</code>: The JavaScript value to check.</li> 3196<li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a <code>node::Buffer</code> 3197object.</li> 3198</ul> 3199<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3200<p>This API checks if the <code>Object</code> passed in is a buffer.</p> 3201<h4>napi_is_date<span><a class="mark" href="#n_api_napi_is_date" id="n_api_napi_is_date">#</a></span></h4> 3202<div class="api_metadata"> 3203<span>Added in: v11.11.0, v10.17.0</span> 3204<span>N-API version: 5</span> 3205</div> 3206<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> 3207<ul> 3208<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3209<li><code>[in] value</code>: The JavaScript value to check.</li> 3210<li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a JavaScript <code>Date</code> 3211object.</li> 3212</ul> 3213<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3214<p>This API checks if the <code>Object</code> passed in is a date.</p> 3215<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> 3216<div class="api_metadata"> 3217<span>Added in: v8.0.0</span> 3218<span>N-API version: 1</span> 3219</div> 3220<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> 3221<ul> 3222<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3223<li><code>[in] value</code>: The JavaScript value to check.</li> 3224<li><code>[out] result</code>: Whether the given <code>napi_value</code> represents an <code>Error</code> object.</li> 3225</ul> 3226<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3227<p>This API checks if the <code>Object</code> passed in is an <code>Error</code>.</p> 3228<h4>napi_is_typedarray<span><a class="mark" href="#n_api_napi_is_typedarray" id="n_api_napi_is_typedarray">#</a></span></h4> 3229<div class="api_metadata"> 3230<span>Added in: v8.0.0</span> 3231<span>N-API version: 1</span> 3232</div> 3233<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> 3234<ul> 3235<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3236<li><code>[in] value</code>: The JavaScript value to check.</li> 3237<li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a <code>TypedArray</code>.</li> 3238</ul> 3239<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3240<p>This API checks if the <code>Object</code> passed in is a typed array.</p> 3241<h4>napi_is_dataview<span><a class="mark" href="#n_api_napi_is_dataview" id="n_api_napi_is_dataview">#</a></span></h4> 3242<div class="api_metadata"> 3243<span>Added in: v8.3.0</span> 3244<span>N-API version: 1</span> 3245</div> 3246<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> 3247<ul> 3248<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3249<li><code>[in] value</code>: The JavaScript value to check.</li> 3250<li><code>[out] result</code>: Whether the given <code>napi_value</code> represents a <code>DataView</code>.</li> 3251</ul> 3252<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3253<p>This API checks if the <code>Object</code> passed in is a <code>DataView</code>.</p> 3254<h4>napi_strict_equals<span><a class="mark" href="#n_api_napi_strict_equals" id="n_api_napi_strict_equals">#</a></span></h4> 3255<div class="api_metadata"> 3256<span>Added in: v8.0.0</span> 3257<span>N-API version: 1</span> 3258</div> 3259<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_strict_equals</span><span class="hljs-params">(napi_env env, 3260 napi_value lhs, 3261 napi_value rhs, 3262 <span class="hljs-type">bool</span>* result)</span></code></pre> 3263<ul> 3264<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3265<li><code>[in] lhs</code>: The JavaScript value to check.</li> 3266<li><code>[in] rhs</code>: The JavaScript value to check against.</li> 3267<li><code>[out] result</code>: Whether the two <code>napi_value</code> objects are equal.</li> 3268</ul> 3269<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3270<p>This API represents the invocation of the Strict Equality algorithm as 3271defined in <a href="https://tc39.github.io/ecma262/#sec-strict-equality-comparison">Section 7.2.14</a> of the ECMAScript Language Specification.</p> 3272<h4>napi_detach_arraybuffer<span><a class="mark" href="#n_api_napi_detach_arraybuffer" id="n_api_napi_detach_arraybuffer">#</a></span></h4> 3273<div class="api_metadata"> 3274<span>Added in: v13.0.0, v12.16.0, v10.22.0</span> 3275<span>N-API version: 7</span> 3276</div> 3277<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_detach_arraybuffer</span><span class="hljs-params">(napi_env env, 3278 napi_value arraybuffer)</span></code></pre> 3279<ul> 3280<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3281<li><code>[in] arraybuffer</code>: The JavaScript <code>ArrayBuffer</code> to be detached.</li> 3282</ul> 3283<p>Returns <code>napi_ok</code> if the API succeeded. If a non-detachable <code>ArrayBuffer</code> is 3284passed in it returns <code>napi_detachable_arraybuffer_expected</code>.</p> 3285<p>Generally, an <code>ArrayBuffer</code> is non-detachable if it has been detached before. 3286The engine may impose additional conditions on whether an <code>ArrayBuffer</code> is 3287detachable. For example, V8 requires that the <code>ArrayBuffer</code> be external, 3288that is, created with <a href="#n_api_napi_create_external_arraybuffer"><code>napi_create_external_arraybuffer</code></a>.</p> 3289<p>This API represents the invocation of the <code>ArrayBuffer</code> detach operation as 3290defined in <a href="https://tc39.es/ecma262/#sec-detacharraybuffer">Section 24.1.1.3</a> of the ECMAScript Language Specification.</p> 3291<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> 3292<div class="api_metadata"> 3293<span>Added in: v13.3.0, v12.16.0, v10.22.0</span> 3294<span>N-API version: 7</span> 3295</div> 3296<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_detached_arraybuffer</span><span class="hljs-params">(napi_env env, 3297 napi_value arraybuffer, 3298 <span class="hljs-type">bool</span>* result)</span></code></pre> 3299<ul> 3300<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3301<li><code>[in] arraybuffer</code>: The JavaScript <code>ArrayBuffer</code> to be checked.</li> 3302<li><code>[out] result</code>: Whether the <code>arraybuffer</code> is detached.</li> 3303</ul> 3304<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3305<p>The <code>ArrayBuffer</code> is considered detached if its internal data is <code>null</code>.</p> 3306<p>This API represents the invocation of the <code>ArrayBuffer</code> <code>IsDetachedBuffer</code> 3307operation as defined in <a href="https://tc39.es/ecma262/#sec-isdetachedbuffer">Section 24.1.1.2</a> of the ECMAScript Language 3308Specification.</p> 3309</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> 3310<p>Node-API exposes a set of APIs to get and set properties on JavaScript 3311objects. Some of these types are documented under <a href="https://tc39.github.io/ecma262/#sec-abstract-operations">Section 7</a> of the 3312<a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>.</p> 3313<p>Properties in JavaScript are represented as a tuple of a key and a value. 3314Fundamentally, all property keys in Node-API can be represented in one of the 3315following forms:</p> 3316<ul> 3317<li>Named: a simple UTF8-encoded string</li> 3318<li>Integer-Indexed: an index value represented by <code>uint32_t</code></li> 3319<li>JavaScript value: these are represented in Node-API by <code>napi_value</code>. This can 3320be a <code>napi_value</code> representing a <code>string</code>, <code>number</code>, or <code>symbol</code>.</li> 3321</ul> 3322<p>Node-API values are represented by the type <code>napi_value</code>. 3323Any Node-API call that requires a JavaScript value takes in a <code>napi_value</code>. 3324However, it's the caller's responsibility to make sure that the 3325<code>napi_value</code> in question is of the JavaScript type expected by the API.</p> 3326<p>The APIs documented in this section provide a simple interface to 3327get and set properties on arbitrary JavaScript objects represented by 3328<code>napi_value</code>.</p> 3329<p>For instance, consider the following JavaScript code snippet:</p> 3330<pre><code class="language-js"><span class="hljs-keyword">const</span> obj = {}; 3331obj.<span class="hljs-property">myProp</span> = <span class="hljs-number">123</span>;</code></pre> 3332<p>The equivalent can be done using Node-API values with the following snippet:</p> 3333<pre><code class="language-c">napi_status status = napi_generic_failure; 3334 3335<span class="hljs-comment">// const obj = {}</span> 3336napi_value obj, value; 3337status = napi_create_object(env, &obj); 3338<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3339 3340<span class="hljs-comment">// Create a napi_value for 123</span> 3341status = napi_create_int32(env, <span class="hljs-number">123</span>, &value); 3342<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3343 3344<span class="hljs-comment">// obj.myProp = 123</span> 3345status = napi_set_named_property(env, obj, <span class="hljs-string">"myProp"</span>, value); 3346<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3347<p>Indexed properties can be set in a similar manner. Consider the following 3348JavaScript snippet:</p> 3349<pre><code class="language-js"><span class="hljs-keyword">const</span> arr = []; 3350arr[<span class="hljs-number">123</span>] = <span class="hljs-string">'hello'</span>;</code></pre> 3351<p>The equivalent can be done using Node-API values with the following snippet:</p> 3352<pre><code class="language-c">napi_status status = napi_generic_failure; 3353 3354<span class="hljs-comment">// const arr = [];</span> 3355napi_value arr, value; 3356status = napi_create_array(env, &arr); 3357<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3358 3359<span class="hljs-comment">// Create a napi_value for 'hello'</span> 3360status = napi_create_string_utf8(env, <span class="hljs-string">"hello"</span>, NAPI_AUTO_LENGTH, &value); 3361<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3362 3363<span class="hljs-comment">// arr[123] = 'hello';</span> 3364status = napi_set_element(env, arr, <span class="hljs-number">123</span>, value); 3365<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3366<p>Properties can be retrieved using the APIs described in this section. 3367Consider the following JavaScript snippet:</p> 3368<pre><code class="language-js"><span class="hljs-keyword">const</span> arr = []; 3369<span class="hljs-keyword">const</span> value = arr[<span class="hljs-number">123</span>];</code></pre> 3370<p>The following is the approximate equivalent of the Node-API counterpart:</p> 3371<pre><code class="language-c">napi_status status = napi_generic_failure; 3372 3373<span class="hljs-comment">// const arr = []</span> 3374napi_value arr, value; 3375status = napi_create_array(env, &arr); 3376<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3377 3378<span class="hljs-comment">// const value = arr[123]</span> 3379status = napi_get_element(env, arr, <span class="hljs-number">123</span>, &value); 3380<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3381<p>Finally, multiple properties can also be defined on an object for performance 3382reasons. Consider the following JavaScript:</p> 3383<pre><code class="language-js"><span class="hljs-keyword">const</span> obj = {}; 3384<span class="hljs-title class_">Object</span>.<span class="hljs-title function_">defineProperties</span>(obj, { 3385 <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> }, 3386 <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> } 3387});</code></pre> 3388<p>The following is the approximate equivalent of the Node-API counterpart:</p> 3389<pre><code class="language-c">napi_status status = napi_status_generic_failure; 3390 3391<span class="hljs-comment">// const obj = {};</span> 3392napi_value obj; 3393status = napi_create_object(env, &obj); 3394<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3395 3396<span class="hljs-comment">// Create napi_values for 123 and 456</span> 3397napi_value fooValue, barValue; 3398status = napi_create_int32(env, <span class="hljs-number">123</span>, &fooValue); 3399<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3400status = napi_create_int32(env, <span class="hljs-number">456</span>, &barValue); 3401<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status; 3402 3403<span class="hljs-comment">// Set the properties</span> 3404napi_property_descriptor descriptors[] = { 3405 { <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> }, 3406 { <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> } 3407} 3408status = napi_define_properties(env, 3409 obj, 3410 <span class="hljs-keyword">sizeof</span>(descriptors) / <span class="hljs-keyword">sizeof</span>(descriptors[<span class="hljs-number">0</span>]), 3411 descriptors); 3412<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> status;</code></pre> 3413<h4>Structures<span><a class="mark" href="#n_api_structures" id="n_api_structures">#</a></span></h4> 3414<h5>napi_property_attributes<span><a class="mark" href="#n_api_napi_property_attributes" id="n_api_napi_property_attributes">#</a></span></h5> 3415<div class="api_metadata"> 3416<details class="changelog"><summary>History</summary> 3417<table> 3418<tbody><tr><th>Version</th><th>Changes</th></tr> 3419<tr><td>v14.12.0</td> 3420<td><p>added <code>napi_default_method</code> and <code>napi_default_property</code>.</p></td></tr> 3421</tbody></table> 3422</details> 3423</div> 3424<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">enum</span> {</span> 3425 napi_default = <span class="hljs-number">0</span>, 3426 napi_writable = <span class="hljs-number">1</span> << <span class="hljs-number">0</span>, 3427 napi_enumerable = <span class="hljs-number">1</span> << <span class="hljs-number">1</span>, 3428 napi_configurable = <span class="hljs-number">1</span> << <span class="hljs-number">2</span>, 3429 3430 <span class="hljs-comment">// Used with napi_define_class to distinguish static properties</span> 3431 <span class="hljs-comment">// from instance properties. Ignored by napi_define_properties.</span> 3432 napi_static = <span class="hljs-number">1</span> << <span class="hljs-number">10</span>, 3433 3434 <span class="hljs-comment">// Default for class methods.</span> 3435 napi_default_method = napi_writable | napi_configurable, 3436 3437 <span class="hljs-comment">// Default for object properties, like in JS obj[prop].</span> 3438 napi_default_jsproperty = napi_writable | 3439 napi_enumerable | 3440 napi_configurable, 3441} napi_property_attributes;</code></pre> 3442<p><code>napi_property_attributes</code> are flags used to control the behavior of properties 3443set on a JavaScript object. Other than <code>napi_static</code> they correspond to the 3444attributes listed in <a href="https://tc39.github.io/ecma262/#table-2">Section 6.1.7.1</a> 3445of the <a href="https://tc39.github.io/ecma262/">ECMAScript Language Specification</a>. 3446They can be one or more of the following bitflags:</p> 3447<ul> 3448<li><code>napi_default</code>: No explicit attributes are set on the property. By default, a 3449property is read only, not enumerable and not configurable.</li> 3450<li><code>napi_writable</code>: The property is writable.</li> 3451<li><code>napi_enumerable</code>: The property is enumerable.</li> 3452<li><code>napi_configurable</code>: The property is configurable as defined in 3453<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> 3454<li><code>napi_static</code>: The property will be defined as a static property on a class as 3455opposed to an instance property, which is the default. This is used only by 3456<a href="#n_api_napi_define_class"><code>napi_define_class</code></a>. It is ignored by <code>napi_define_properties</code>.</li> 3457<li><code>napi_default_method</code>: Like a method in a JS class, the property is 3458configurable and writeable, but not enumerable.</li> 3459<li><code>napi_default_jsproperty</code>: Like a property set via assignment in JavaScript, 3460the property is writable, enumerable, and configurable.</li> 3461</ul> 3462<h5>napi_property_descriptor<span><a class="mark" href="#n_api_napi_property_descriptor" id="n_api_napi_property_descriptor">#</a></span></h5> 3463<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 3464 <span class="hljs-comment">// One of utf8name or name should be NULL.</span> 3465 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8name; 3466 napi_value name; 3467 3468 napi_callback method; 3469 napi_callback getter; 3470 napi_callback setter; 3471 napi_value value; 3472 3473 napi_property_attributes attributes; 3474 <span class="hljs-type">void</span>* data; 3475} napi_property_descriptor;</code></pre> 3476<ul> 3477<li><code>utf8name</code>: Optional string describing the key for the property, 3478encoded as UTF8. One of <code>utf8name</code> or <code>name</code> must be provided for the 3479property.</li> 3480<li><code>name</code>: Optional <code>napi_value</code> that points to a JavaScript string or symbol 3481to be used as the key for the property. One of <code>utf8name</code> or <code>name</code> must 3482be provided for the property.</li> 3483<li><code>value</code>: The value that's retrieved by a get access of the property if the 3484property is a data property. If this is passed in, set <code>getter</code>, <code>setter</code>, 3485<code>method</code> and <code>data</code> to <code>NULL</code> (since these members won't be used).</li> 3486<li><code>getter</code>: A function to call when a get access of the property is performed. 3487If this is passed in, set <code>value</code> and <code>method</code> to <code>NULL</code> (since these members 3488won't be used). The given function is called implicitly by the runtime when 3489the property is accessed from JavaScript code (or if a get on the property is 3490performed using a Node-API call). <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3491<li><code>setter</code>: A function to call when a set access of the property is performed. 3492If this is passed in, set <code>value</code> and <code>method</code> to <code>NULL</code> (since these members 3493won't be used). The given function is called implicitly by the runtime when 3494the property is set from JavaScript code (or if a set on the property is 3495performed using a Node-API call). <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3496<li><code>method</code>: Set this to make the property descriptor object's <code>value</code> 3497property to be a JavaScript function represented by <code>method</code>. If this is 3498passed in, set <code>value</code>, <code>getter</code> and <code>setter</code> to <code>NULL</code> (since these members 3499won't be used). <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3500<li><code>attributes</code>: The attributes associated with the particular property. See 3501<a href="#n_api_napi_property_attributes"><code>napi_property_attributes</code></a>.</li> 3502<li><code>data</code>: The callback data passed into <code>method</code>, <code>getter</code> and <code>setter</code> if this 3503function is invoked.</li> 3504</ul> 3505<h4>Functions<span><a class="mark" href="#n_api_functions" id="n_api_functions">#</a></span></h4> 3506<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> 3507<div class="api_metadata"> 3508<span>Added in: v8.0.0</span> 3509<span>N-API version: 1</span> 3510</div> 3511<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_property_names</span><span class="hljs-params">(napi_env env, 3512 napi_value object, 3513 napi_value* result)</span>;</code></pre> 3514<ul> 3515<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3516<li><code>[in] object</code>: The object from which to retrieve the properties.</li> 3517<li><code>[out] result</code>: A <code>napi_value</code> representing an array of JavaScript values 3518that represent the property names of the object. The API can be used to 3519iterate over <code>result</code> using <a href="#n_api_napi_get_array_length"><code>napi_get_array_length</code></a> 3520and <a href="#n_api_napi_get_element"><code>napi_get_element</code></a>.</li> 3521</ul> 3522<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3523<p>This API returns the names of the enumerable properties of <code>object</code> as an array 3524of strings. The properties of <code>object</code> whose key is a symbol will not be 3525included.</p> 3526<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> 3527<div class="api_metadata"> 3528<span>Added in: v13.7.0, v10.20.0</span> 3529<span>N-API version: 6</span> 3530</div> 3531<pre><code class="language-c">napi_get_all_property_names(napi_env env, 3532 napi_value object, 3533 napi_key_collection_mode key_mode, 3534 napi_key_filter key_filter, 3535 napi_key_conversion key_conversion, 3536 napi_value* result);</code></pre> 3537<ul> 3538<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3539<li><code>[in] object</code>: The object from which to retrieve the properties.</li> 3540<li><code>[in] key_mode</code>: Whether to retrieve prototype properties as well.</li> 3541<li><code>[in] key_filter</code>: Which properties to retrieve 3542(enumerable/readable/writable).</li> 3543<li><code>[in] key_conversion</code>: Whether to convert numbered property keys to strings.</li> 3544<li><code>[out] result</code>: A <code>napi_value</code> representing an array of JavaScript values 3545that represent the property names of the object. <a href="#n_api_napi_get_array_length"><code>napi_get_array_length</code></a> 3546and <a href="#n_api_napi_get_element"><code>napi_get_element</code></a> can be used to iterate over <code>result</code>.</li> 3547</ul> 3548<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3549<p>This API returns an array containing the names of the available properties 3550of this object.</p> 3551<h5>napi_set_property<span><a class="mark" href="#n_api_napi_set_property" id="n_api_napi_set_property">#</a></span></h5> 3552<div class="api_metadata"> 3553<span>Added in: v8.0.0</span> 3554<span>N-API version: 1</span> 3555</div> 3556<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_property</span><span class="hljs-params">(napi_env env, 3557 napi_value object, 3558 napi_value key, 3559 napi_value value)</span>;</code></pre> 3560<ul> 3561<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3562<li><code>[in] object</code>: The object on which to set the property.</li> 3563<li><code>[in] key</code>: The name of the property to set.</li> 3564<li><code>[in] value</code>: The property value.</li> 3565</ul> 3566<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3567<p>This API set a property on the <code>Object</code> passed in.</p> 3568<h5>napi_get_property<span><a class="mark" href="#n_api_napi_get_property" id="n_api_napi_get_property">#</a></span></h5> 3569<div class="api_metadata"> 3570<span>Added in: v8.0.0</span> 3571<span>N-API version: 1</span> 3572</div> 3573<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_property</span><span class="hljs-params">(napi_env env, 3574 napi_value object, 3575 napi_value key, 3576 napi_value* result)</span>;</code></pre> 3577<ul> 3578<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3579<li><code>[in] object</code>: The object from which to retrieve the property.</li> 3580<li><code>[in] key</code>: The name of the property to retrieve.</li> 3581<li><code>[out] result</code>: The value of the property.</li> 3582</ul> 3583<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3584<p>This API gets the requested property from the <code>Object</code> passed in.</p> 3585<h5>napi_has_property<span><a class="mark" href="#n_api_napi_has_property" id="n_api_napi_has_property">#</a></span></h5> 3586<div class="api_metadata"> 3587<span>Added in: v8.0.0</span> 3588<span>N-API version: 1</span> 3589</div> 3590<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_property</span><span class="hljs-params">(napi_env env, 3591 napi_value object, 3592 napi_value key, 3593 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3594<ul> 3595<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3596<li><code>[in] object</code>: The object to query.</li> 3597<li><code>[in] key</code>: The name of the property whose existence to check.</li> 3598<li><code>[out] result</code>: Whether the property exists on the object or not.</li> 3599</ul> 3600<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3601<p>This API checks if the <code>Object</code> passed in has the named property.</p> 3602<h5>napi_delete_property<span><a class="mark" href="#n_api_napi_delete_property" id="n_api_napi_delete_property">#</a></span></h5> 3603<div class="api_metadata"> 3604<span>Added in: v8.2.0</span> 3605<span>N-API version: 1</span> 3606</div> 3607<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_delete_property</span><span class="hljs-params">(napi_env env, 3608 napi_value object, 3609 napi_value key, 3610 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3611<ul> 3612<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3613<li><code>[in] object</code>: The object to query.</li> 3614<li><code>[in] key</code>: The name of the property to delete.</li> 3615<li><code>[out] result</code>: Whether the property deletion succeeded or not. <code>result</code> can 3616optionally be ignored by passing <code>NULL</code>.</li> 3617</ul> 3618<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3619<p>This API attempts to delete the <code>key</code> own property from <code>object</code>.</p> 3620<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> 3621<div class="api_metadata"> 3622<span>Added in: v8.2.0</span> 3623<span>N-API version: 1</span> 3624</div> 3625<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_own_property</span><span class="hljs-params">(napi_env env, 3626 napi_value object, 3627 napi_value key, 3628 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3629<ul> 3630<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3631<li><code>[in] object</code>: The object to query.</li> 3632<li><code>[in] key</code>: The name of the own property whose existence to check.</li> 3633<li><code>[out] result</code>: Whether the own property exists on the object or not.</li> 3634</ul> 3635<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3636<p>This API checks if the <code>Object</code> passed in has the named own property. <code>key</code> must 3637be a <code>string</code> or a <code>symbol</code>, or an error will be thrown. Node-API will not 3638perform any conversion between data types.</p> 3639<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> 3640<div class="api_metadata"> 3641<span>Added in: v8.0.0</span> 3642<span>N-API version: 1</span> 3643</div> 3644<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_named_property</span><span class="hljs-params">(napi_env env, 3645 napi_value object, 3646 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8Name, 3647 napi_value value)</span>;</code></pre> 3648<ul> 3649<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3650<li><code>[in] object</code>: The object on which to set the property.</li> 3651<li><code>[in] utf8Name</code>: The name of the property to set.</li> 3652<li><code>[in] value</code>: The property value.</li> 3653</ul> 3654<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3655<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> 3656created from the string passed in as <code>utf8Name</code>.</p> 3657<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> 3658<div class="api_metadata"> 3659<span>Added in: v8.0.0</span> 3660<span>N-API version: 1</span> 3661</div> 3662<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_named_property</span><span class="hljs-params">(napi_env env, 3663 napi_value object, 3664 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8Name, 3665 napi_value* result)</span>;</code></pre> 3666<ul> 3667<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3668<li><code>[in] object</code>: The object from which to retrieve the property.</li> 3669<li><code>[in] utf8Name</code>: The name of the property to get.</li> 3670<li><code>[out] result</code>: The value of the property.</li> 3671</ul> 3672<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3673<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> 3674created from the string passed in as <code>utf8Name</code>.</p> 3675<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> 3676<div class="api_metadata"> 3677<span>Added in: v8.0.0</span> 3678<span>N-API version: 1</span> 3679</div> 3680<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_named_property</span><span class="hljs-params">(napi_env env, 3681 napi_value object, 3682 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8Name, 3683 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3684<ul> 3685<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3686<li><code>[in] object</code>: The object to query.</li> 3687<li><code>[in] utf8Name</code>: The name of the property whose existence to check.</li> 3688<li><code>[out] result</code>: Whether the property exists on the object or not.</li> 3689</ul> 3690<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3691<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> 3692created from the string passed in as <code>utf8Name</code>.</p> 3693<h5>napi_set_element<span><a class="mark" href="#n_api_napi_set_element" id="n_api_napi_set_element">#</a></span></h5> 3694<div class="api_metadata"> 3695<span>Added in: v8.0.0</span> 3696<span>N-API version: 1</span> 3697</div> 3698<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_set_element</span><span class="hljs-params">(napi_env env, 3699 napi_value object, 3700 <span class="hljs-type">uint32_t</span> index, 3701 napi_value value)</span>;</code></pre> 3702<ul> 3703<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3704<li><code>[in] object</code>: The object from which to set the properties.</li> 3705<li><code>[in] index</code>: The index of the property to set.</li> 3706<li><code>[in] value</code>: The property value.</li> 3707</ul> 3708<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3709<p>This API sets and element on the <code>Object</code> passed in.</p> 3710<h5>napi_get_element<span><a class="mark" href="#n_api_napi_get_element" id="n_api_napi_get_element">#</a></span></h5> 3711<div class="api_metadata"> 3712<span>Added in: v8.0.0</span> 3713<span>N-API version: 1</span> 3714</div> 3715<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_element</span><span class="hljs-params">(napi_env env, 3716 napi_value object, 3717 <span class="hljs-type">uint32_t</span> index, 3718 napi_value* result)</span>;</code></pre> 3719<ul> 3720<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3721<li><code>[in] object</code>: The object from which to retrieve the property.</li> 3722<li><code>[in] index</code>: The index of the property to get.</li> 3723<li><code>[out] result</code>: The value of the property.</li> 3724</ul> 3725<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3726<p>This API gets the element at the requested index.</p> 3727<h5>napi_has_element<span><a class="mark" href="#n_api_napi_has_element" id="n_api_napi_has_element">#</a></span></h5> 3728<div class="api_metadata"> 3729<span>Added in: v8.0.0</span> 3730<span>N-API version: 1</span> 3731</div> 3732<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_has_element</span><span class="hljs-params">(napi_env env, 3733 napi_value object, 3734 <span class="hljs-type">uint32_t</span> index, 3735 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3736<ul> 3737<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3738<li><code>[in] object</code>: The object to query.</li> 3739<li><code>[in] index</code>: The index of the property whose existence to check.</li> 3740<li><code>[out] result</code>: Whether the property exists on the object or not.</li> 3741</ul> 3742<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3743<p>This API returns if the <code>Object</code> passed in has an element at the 3744requested index.</p> 3745<h5>napi_delete_element<span><a class="mark" href="#n_api_napi_delete_element" id="n_api_napi_delete_element">#</a></span></h5> 3746<div class="api_metadata"> 3747<span>Added in: v8.2.0</span> 3748<span>N-API version: 1</span> 3749</div> 3750<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_delete_element</span><span class="hljs-params">(napi_env env, 3751 napi_value object, 3752 <span class="hljs-type">uint32_t</span> index, 3753 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 3754<ul> 3755<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3756<li><code>[in] object</code>: The object to query.</li> 3757<li><code>[in] index</code>: The index of the property to delete.</li> 3758<li><code>[out] result</code>: Whether the element deletion succeeded or not. <code>result</code> can 3759optionally be ignored by passing <code>NULL</code>.</li> 3760</ul> 3761<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3762<p>This API attempts to delete the specified <code>index</code> from <code>object</code>.</p> 3763<h5>napi_define_properties<span><a class="mark" href="#n_api_napi_define_properties" id="n_api_napi_define_properties">#</a></span></h5> 3764<div class="api_metadata"> 3765<span>Added in: v8.0.0</span> 3766<span>N-API version: 1</span> 3767</div> 3768<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_define_properties</span><span class="hljs-params">(napi_env env, 3769 napi_value object, 3770 <span class="hljs-type">size_t</span> property_count, 3771 <span class="hljs-keyword">const</span> napi_property_descriptor* properties)</span>;</code></pre> 3772<ul> 3773<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3774<li><code>[in] object</code>: The object from which to retrieve the properties.</li> 3775<li><code>[in] property_count</code>: The number of elements in the <code>properties</code> array.</li> 3776<li><code>[in] properties</code>: The array of property descriptors.</li> 3777</ul> 3778<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3779<p>This method allows the efficient definition of multiple properties on a given 3780object. The properties are defined using property descriptors (see 3781<a href="#n_api_napi_property_descriptor"><code>napi_property_descriptor</code></a>). Given an array of such property descriptors, 3782this API will set the properties on the object one at a time, as defined by 3783<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 3784specification).</p> 3785<h5>napi_object_freeze<span><a class="mark" href="#n_api_napi_object_freeze" id="n_api_napi_object_freeze">#</a></span></h5> 3786<div class="api_metadata"> 3787<span>Added in: v14.14.0, v12.20.0</span> 3788<span>N-API version: 8</span> 3789</div> 3790<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_object_freeze</span><span class="hljs-params">(napi_env env, 3791 napi_value object)</span>;</code></pre> 3792<ul> 3793<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3794<li><code>[in] object</code>: The object to freeze.</li> 3795</ul> 3796<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3797<p>This method freezes a given object. This prevents new properties from 3798being added to it, existing properties from being removed, prevents 3799changing the enumerability, configurability, or writability of existing 3800properties, and prevents the values of existing properties from being changed. 3801It also prevents the object's prototype from being changed. This is described 3802in <a href="https://tc39.es/ecma262/#sec-object.freeze">Section 19.1.2.6</a> of the 3803ECMA-262 specification.</p> 3804<h5>napi_object_seal<span><a class="mark" href="#n_api_napi_object_seal" id="n_api_napi_object_seal">#</a></span></h5> 3805<div class="api_metadata"> 3806<span>Added in: v14.14.0, v12.20.0</span> 3807<span>N-API version: 8</span> 3808</div> 3809<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_object_seal</span><span class="hljs-params">(napi_env env, 3810 napi_value object)</span>;</code></pre> 3811<ul> 3812<li><code>[in] env</code>: The environment that the Node-API call is invoked under.</li> 3813<li><code>[in] object</code>: The object to seal.</li> 3814</ul> 3815<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3816<p>This method seals a given object. This prevents new properties from being 3817added to it, as well as marking all existing properties as non-configurable. 3818This is described in <a href="https://tc39.es/ecma262/#sec-object.seal">Section 19.1.2.20</a> 3819of the ECMA-262 specification.</p> 3820</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> 3821<p>Node-API provides a set of APIs that allow JavaScript code to 3822call back into native code. Node-APIs that support calling back 3823into native code take in a callback functions represented by 3824the <code>napi_callback</code> type. When the JavaScript VM calls back to 3825native code, the <code>napi_callback</code> function provided is invoked. The APIs 3826documented in this section allow the callback function to do the 3827following:</p> 3828<ul> 3829<li>Get information about the context in which the callback was invoked.</li> 3830<li>Get the arguments passed into the callback.</li> 3831<li>Return a <code>napi_value</code> back from the callback.</li> 3832</ul> 3833<p>Additionally, Node-API provides a set of functions which allow calling 3834JavaScript functions from native code. One can either call a function 3835like a regular JavaScript function call, or as a constructor 3836function.</p> 3837<p>Any non-<code>NULL</code> data which is passed to this API via the <code>data</code> field of the 3838<code>napi_property_descriptor</code> items can be associated with <code>object</code> and freed 3839whenever <code>object</code> is garbage-collected by passing both <code>object</code> and the data to 3840<a href="#n_api_napi_add_finalizer"><code>napi_add_finalizer</code></a>.</p> 3841<h4>napi_call_function<span><a class="mark" href="#n_api_napi_call_function" id="n_api_napi_call_function">#</a></span></h4> 3842<div class="api_metadata"> 3843<span>Added in: v8.0.0</span> 3844<span>N-API version: 1</span> 3845</div> 3846<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, 3847 napi_value recv, 3848 napi_value func, 3849 <span class="hljs-type">size_t</span> argc, 3850 <span class="hljs-keyword">const</span> napi_value* argv, 3851 napi_value* result)</span>;</code></pre> 3852<ul> 3853<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3854<li><code>[in] recv</code>: The <code>this</code> value passed to the called function.</li> 3855<li><code>[in] func</code>: <code>napi_value</code> representing the JavaScript function to be invoked.</li> 3856<li><code>[in] argc</code>: The count of elements in the <code>argv</code> array.</li> 3857<li><code>[in] argv</code>: Array of <code>napi_values</code> representing JavaScript values passed in 3858as arguments to the function.</li> 3859<li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript object returned.</li> 3860</ul> 3861<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3862<p>This method allows a JavaScript function object to be called from a native 3863add-on. This is the primary mechanism of calling back <em>from</em> the add-on's 3864native code <em>into</em> JavaScript. For the special case of calling into JavaScript 3865after an async operation, see <a href="#n_api_napi_make_callback"><code>napi_make_callback</code></a>.</p> 3866<p>A sample use case might look as follows. Consider the following JavaScript 3867snippet:</p> 3868<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">AddTwo</span>(<span class="hljs-params">num</span>) { 3869 <span class="hljs-keyword">return</span> num + <span class="hljs-number">2</span>; 3870}</code></pre> 3871<p>Then, the above function can be invoked from a native add-on using the 3872following code:</p> 3873<pre><code class="language-c"><span class="hljs-comment">// Get the function named "AddTwo" on the global object</span> 3874napi_value global, add_two, arg; 3875napi_status status = napi_get_global(env, &global); 3876<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3877 3878status = napi_get_named_property(env, global, <span class="hljs-string">"AddTwo"</span>, &add_two); 3879<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3880 3881<span class="hljs-comment">// const arg = 1337</span> 3882status = napi_create_int32(env, <span class="hljs-number">1337</span>, &arg); 3883<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3884 3885napi_value* argv = &arg; 3886<span class="hljs-type">size_t</span> argc = <span class="hljs-number">1</span>; 3887 3888<span class="hljs-comment">// AddTwo(arg);</span> 3889napi_value return_val; 3890status = napi_call_function(env, global, add_two, argc, argv, &return_val); 3891<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 3892 3893<span class="hljs-comment">// Convert the result back to a native type</span> 3894<span class="hljs-type">int32_t</span> result; 3895status = napi_get_value_int32(env, return_val, &result); 3896<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>;</code></pre> 3897<h4>napi_create_function<span><a class="mark" href="#n_api_napi_create_function" id="n_api_napi_create_function">#</a></span></h4> 3898<div class="api_metadata"> 3899<span>Added in: v8.0.0</span> 3900<span>N-API version: 1</span> 3901</div> 3902<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_function</span><span class="hljs-params">(napi_env env, 3903 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8name, 3904 <span class="hljs-type">size_t</span> length, 3905 napi_callback cb, 3906 <span class="hljs-type">void</span>* data, 3907 napi_value* result)</span>;</code></pre> 3908<ul> 3909<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3910<li><code>[in] utf8Name</code>: The name of the function encoded as UTF8. This is visible 3911within JavaScript as the new function object's <code>name</code> property.</li> 3912<li><code>[in] length</code>: The length of the <code>utf8name</code> in bytes, or <code>NAPI_AUTO_LENGTH</code> if 3913it is null-terminated.</li> 3914<li><code>[in] cb</code>: The native function which should be called when this function 3915object is invoked. <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 3916<li><code>[in] data</code>: User-provided data context. This will be passed back into the 3917function when invoked later.</li> 3918<li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript function object for 3919the newly created function.</li> 3920</ul> 3921<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3922<p>This API allows an add-on author to create a function object in native code. 3923This is the primary mechanism to allow calling <em>into</em> the add-on's native code 3924<em>from</em> JavaScript.</p> 3925<p>The newly created function is not automatically visible from script after this 3926call. Instead, a property must be explicitly set on any object that is visible 3927to JavaScript, in order for the function to be accessible from script.</p> 3928<p>In order to expose a function as part of the 3929add-on's module exports, set the newly created function on the exports 3930object. A sample module might look as follows:</p> 3931<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> { 3932 <span class="hljs-built_in">printf</span>(<span class="hljs-string">"Hello\n"</span>); 3933 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 3934} 3935 3936napi_value <span class="hljs-title function_">Init</span><span class="hljs-params">(napi_env env, napi_value exports)</span> { 3937 napi_status status; 3938 3939 napi_value fn; 3940 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); 3941 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 3942 3943 status = napi_set_named_property(env, exports, <span class="hljs-string">"sayHello"</span>, fn); 3944 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 3945 3946 <span class="hljs-keyword">return</span> exports; 3947} 3948 3949NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)</code></pre> 3950<p>Given the above code, the add-on can be used from JavaScript as follows:</p> 3951<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>); 3952myaddon.<span class="hljs-title function_">sayHello</span>();</code></pre> 3953<p>The string passed to <code>require()</code> is the name of the target in <code>binding.gyp</code> 3954responsible for creating the <code>.node</code> file.</p> 3955<p>Any non-<code>NULL</code> data which is passed to this API via the <code>data</code> parameter can 3956be associated with the resulting JavaScript function (which is returned in the 3957<code>result</code> parameter) and freed whenever the function is garbage-collected by 3958passing both the JavaScript function and the data to <a href="#n_api_napi_add_finalizer"><code>napi_add_finalizer</code></a>.</p> 3959<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 3960Language Specification.</p> 3961<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> 3962<div class="api_metadata"> 3963<span>Added in: v8.0.0</span> 3964<span>N-API version: 1</span> 3965</div> 3966<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_cb_info</span><span class="hljs-params">(napi_env env, 3967 napi_callback_info cbinfo, 3968 <span class="hljs-type">size_t</span>* argc, 3969 napi_value* argv, 3970 napi_value* thisArg, 3971 <span class="hljs-type">void</span>** data)</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>[in-out] argc</code>: Specifies the length of the provided <code>argv</code> array and 3976receives the actual count of arguments.</li> 3977<li><code>[out] argv</code>: Buffer to which the <code>napi_value</code> representing the arguments are 3978copied. If there are more arguments than the provided count, only the 3979requested number of arguments are copied. If there are fewer arguments 3980provided than claimed, the rest of <code>argv</code> is filled with <code>napi_value</code> values 3981that represent <code>undefined</code>.</li> 3982<li><code>[out] this</code>: Receives the JavaScript <code>this</code> argument for the call.</li> 3983<li><code>[out] data</code>: Receives the data pointer for the callback.</li> 3984</ul> 3985<p>Returns <code>napi_ok</code> if the API succeeded.</p> 3986<p>This method is used within a callback function to retrieve details about the 3987call like the arguments and the <code>this</code> pointer from a given callback info.</p> 3988<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> 3989<div class="api_metadata"> 3990<span>Added in: v8.6.0</span> 3991<span>N-API version: 1</span> 3992</div> 3993<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_new_target</span><span class="hljs-params">(napi_env env, 3994 napi_callback_info cbinfo, 3995 napi_value* result)</span></code></pre> 3996<ul> 3997<li><code>[in] env</code>: The environment that the API is invoked under.</li> 3998<li><code>[in] cbinfo</code>: The callback info passed into the callback function.</li> 3999<li><code>[out] result</code>: The <code>new.target</code> of the constructor call.</li> 4000</ul> 4001<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4002<p>This API returns the <code>new.target</code> of the constructor call. If the current 4003callback is not a constructor call, the result is <code>NULL</code>.</p> 4004<h4>napi_new_instance<span><a class="mark" href="#n_api_napi_new_instance" id="n_api_napi_new_instance">#</a></span></h4> 4005<div class="api_metadata"> 4006<span>Added in: v8.0.0</span> 4007<span>N-API version: 1</span> 4008</div> 4009<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_new_instance</span><span class="hljs-params">(napi_env env, 4010 napi_value cons, 4011 <span class="hljs-type">size_t</span> argc, 4012 napi_value* argv, 4013 napi_value* result)</span></code></pre> 4014<ul> 4015<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4016<li><code>[in] cons</code>: <code>napi_value</code> representing the JavaScript function to be invoked 4017as a constructor.</li> 4018<li><code>[in] argc</code>: The count of elements in the <code>argv</code> array.</li> 4019<li><code>[in] argv</code>: Array of JavaScript values as <code>napi_value</code> representing the 4020arguments to the constructor.</li> 4021<li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript object returned, 4022which in this case is the constructed object.</li> 4023</ul> 4024<p>This method is used to instantiate a new JavaScript value using a given 4025<code>napi_value</code> that represents the constructor for the object. For example, 4026consider the following snippet:</p> 4027<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">MyObject</span>(<span class="hljs-params">param</span>) { 4028 <span class="hljs-variable language_">this</span>.<span class="hljs-property">param</span> = param; 4029} 4030 4031<span class="hljs-keyword">const</span> arg = <span class="hljs-string">'hello'</span>; 4032<span class="hljs-keyword">const</span> value = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyObject</span>(arg);</code></pre> 4033<p>The following can be approximated in Node-API using the following snippet:</p> 4034<pre><code class="language-c"><span class="hljs-comment">// Get the constructor function MyObject</span> 4035napi_value global, constructor, arg, value; 4036napi_status status = napi_get_global(env, &global); 4037<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 4038 4039status = napi_get_named_property(env, global, <span class="hljs-string">"MyObject"</span>, &constructor); 4040<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 4041 4042<span class="hljs-comment">// const arg = "hello"</span> 4043status = napi_create_string_utf8(env, <span class="hljs-string">"hello"</span>, NAPI_AUTO_LENGTH, &arg); 4044<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span>; 4045 4046napi_value* argv = &arg; 4047<span class="hljs-type">size_t</span> argc = <span class="hljs-number">1</span>; 4048 4049<span class="hljs-comment">// const value = new MyObject(arg)</span> 4050status = napi_new_instance(env, constructor, argc, argv, &value);</code></pre> 4051<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4052</section><section><h3>Object wrap<span><a class="mark" href="#n_api_object_wrap" id="n_api_object_wrap">#</a></span></h3> 4053<p>Node-API offers a way to "wrap" C++ classes and instances so that the class 4054constructor and methods can be called from JavaScript.</p> 4055<ol> 4056<li>The <a href="#n_api_napi_define_class"><code>napi_define_class</code></a> API defines a JavaScript class with constructor, 4057static properties and methods, and instance properties and methods that 4058correspond to the C++ class.</li> 4059<li>When JavaScript code invokes the constructor, the constructor callback 4060uses <a href="#n_api_napi_wrap"><code>napi_wrap</code></a> to wrap a new C++ instance in a JavaScript object, 4061then returns the wrapper object.</li> 4062<li>When JavaScript code invokes a method or property accessor on the class, 4063the corresponding <code>napi_callback</code> C++ function is invoked. For an instance 4064callback, <a href="#n_api_napi_unwrap"><code>napi_unwrap</code></a> obtains the C++ instance that is the target of 4065the call.</li> 4066</ol> 4067<p>For wrapped objects it may be difficult to distinguish between a function 4068called on a class prototype and a function called on an instance of a class. 4069A common pattern used to address this problem is to save a persistent 4070reference to the class constructor for later <code>instanceof</code> checks.</p> 4071<pre><code class="language-c">napi_value MyClass_constructor = <span class="hljs-literal">NULL</span>; 4072status = napi_get_reference_value(env, MyClass::es_constructor, &MyClass_constructor); 4073assert(napi_ok == status); 4074<span class="hljs-type">bool</span> is_instance = <span class="hljs-literal">false</span>; 4075status = napi_instanceof(env, es_this, MyClass_constructor, &is_instance); 4076assert(napi_ok == status); 4077<span class="hljs-keyword">if</span> (is_instance) { 4078 <span class="hljs-comment">// napi_unwrap() ...</span> 4079} <span class="hljs-keyword">else</span> { 4080 <span class="hljs-comment">// otherwise...</span> 4081}</code></pre> 4082<p>The reference must be freed once it is no longer needed.</p> 4083<p>There are occasions where <code>napi_instanceof()</code> is insufficient for ensuring that 4084a JavaScript object is a wrapper for a certain native type. This is the case 4085especially when wrapped JavaScript objects are passed back into the addon via 4086static methods rather than as the <code>this</code> value of prototype methods. In such 4087cases there is a chance that they may be unwrapped incorrectly.</p> 4088<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>); 4089 4090<span class="hljs-comment">// `openDatabase()` returns a JavaScript object that wraps a native database</span> 4091<span class="hljs-comment">// handle.</span> 4092<span class="hljs-keyword">const</span> dbHandle = myAddon.<span class="hljs-title function_">openDatabase</span>(); 4093 4094<span class="hljs-comment">// `query()` returns a JavaScript object that wraps a native query handle.</span> 4095<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>); 4096 4097<span class="hljs-comment">// There is an accidental error in the line below. The first parameter to</span> 4098<span class="hljs-comment">// `myAddon.queryHasRecords()` should be the database handle (`dbHandle`), not</span> 4099<span class="hljs-comment">// the query handle (`query`), so the correct condition for the while-loop</span> 4100<span class="hljs-comment">// should be</span> 4101<span class="hljs-comment">//</span> 4102<span class="hljs-comment">// myAddon.queryHasRecords(dbHandle, queryHandle)</span> 4103<span class="hljs-comment">//</span> 4104<span class="hljs-keyword">while</span> (myAddon.<span class="hljs-title function_">queryHasRecords</span>(queryHandle, dbHandle)) { 4105 <span class="hljs-comment">// retrieve records</span> 4106}</code></pre> 4107<p>In the above example <code>myAddon.queryHasRecords()</code> is a method that accepts two 4108arguments. The first is a database handle and the second is a query handle. 4109Internally, it unwraps the first argument and casts the resulting pointer to a 4110native database handle. It then unwraps the second argument and casts the 4111resulting pointer to a query handle. If the arguments are passed in the wrong 4112order, the casts will work, however, there is a good chance that the underlying 4113database operation will fail, or will even cause an invalid memory access.</p> 4114<p>To ensure that the pointer retrieved from the first argument is indeed a pointer 4115to a database handle and, similarly, that the pointer retrieved from the second 4116argument is indeed a pointer to a query handle, the implementation of 4117<code>queryHasRecords()</code> has to perform a type validation. Retaining the JavaScript 4118class constructor from which the database handle was instantiated and the 4119constructor from which the query handle was instantiated in <code>napi_ref</code>s can 4120help, because <code>napi_instanceof()</code> can then be used to ensure that the instances 4121passed into <code>queryHashRecords()</code> are indeed of the correct type.</p> 4122<p>Unfortunately, <code>napi_instanceof()</code> does not protect against prototype 4123manipulation. For example, the prototype of the database handle instance can be 4124set to the prototype of the constructor for query handle instances. In this 4125case, the database handle instance can appear as a query handle instance, and it 4126will pass the <code>napi_instanceof()</code> test for a query handle instance, while still 4127containing a pointer to a database handle.</p> 4128<p>To this end, Node-API provides type-tagging capabilities.</p> 4129<p>A type tag is a 128-bit integer unique to the addon. Node-API provides the 4130<code>napi_type_tag</code> structure for storing a type tag. When such a value is passed 4131along with a JavaScript object stored in a <code>napi_value</code> to 4132<code>napi_type_tag_object()</code>, the JavaScript object will be "marked" with the 4133type tag. The "mark" is invisible on the JavaScript side. When a JavaScript 4134object arrives into a native binding, <code>napi_check_object_type_tag()</code> can be used 4135along with the original type tag to determine whether the JavaScript object was 4136previously "marked" with the type tag. This creates a type-checking capability 4137of a higher fidelity than <code>napi_instanceof()</code> can provide, because such type- 4138tagging survives prototype manipulation and addon unloading/reloading.</p> 4139<p>Continuing the above example, the following skeleton addon implementation 4140illustrates the use of <code>napi_type_tag_object()</code> and 4141<code>napi_check_object_type_tag()</code>.</p> 4142<pre><code class="language-c"><span class="hljs-comment">// This value is the type tag for a database handle. The command</span> 4143<span class="hljs-comment">//</span> 4144<span class="hljs-comment">// uuidgen | sed -r -e 's/-//g' -e 's/(.{16})(.*)/0x\1, 0x\2/'</span> 4145<span class="hljs-comment">//</span> 4146<span class="hljs-comment">// can be used to obtain the two values with which to initialize the structure.</span> 4147<span class="hljs-keyword">static</span> <span class="hljs-keyword">const</span> napi_type_tag DatabaseHandleTypeTag = { 4148 <span class="hljs-number">0x1edf75a38336451d</span>, <span class="hljs-number">0xa5ed9ce2e4c00c38</span> 4149}; 4150 4151<span class="hljs-comment">// This value is the type tag for a query handle.</span> 4152<span class="hljs-keyword">static</span> <span class="hljs-keyword">const</span> napi_type_tag QueryHandleTypeTag = { 4153 <span class="hljs-number">0x9c73317f9fad44a3</span>, <span class="hljs-number">0x93c3920bf3b0ad6a</span> 4154}; 4155 4156<span class="hljs-keyword">static</span> napi_value 4157<span class="hljs-title function_">openDatabase</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 4158 napi_status status; 4159 napi_value result; 4160 4161 <span class="hljs-comment">// Perform the underlying action which results in a database handle.</span> 4162 DatabaseHandle* dbHandle = open_database(); 4163 4164 <span class="hljs-comment">// Create a new, empty JS object.</span> 4165 status = napi_create_object(env, &result); 4166 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4167 4168 <span class="hljs-comment">// Tag the object to indicate that it holds a pointer to a `DatabaseHandle`.</span> 4169 status = napi_type_tag_object(env, result, &DatabaseHandleTypeTag); 4170 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4171 4172 <span class="hljs-comment">// Store the pointer to the `DatabaseHandle` structure inside the JS object.</span> 4173 status = napi_wrap(env, result, dbHandle, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>); 4174 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4175 4176 <span class="hljs-keyword">return</span> result; 4177} 4178 4179<span class="hljs-comment">// Later when we receive a JavaScript object purporting to be a database handle</span> 4180<span class="hljs-comment">// we can use `napi_check_object_type_tag()` to ensure that it is indeed such a</span> 4181<span class="hljs-comment">// handle.</span> 4182 4183<span class="hljs-keyword">static</span> napi_value 4184<span class="hljs-title function_">query</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 4185 napi_status status; 4186 <span class="hljs-type">size_t</span> argc = <span class="hljs-number">2</span>; 4187 napi_value argv[<span class="hljs-number">2</span>]; 4188 <span class="hljs-type">bool</span> is_db_handle; 4189 4190 status = napi_get_cb_info(env, info, &argc, argv, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>); 4191 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4192 4193 <span class="hljs-comment">// Check that the object passed as the first parameter has the previously</span> 4194 <span class="hljs-comment">// applied tag.</span> 4195 status = napi_check_object_type_tag(env, 4196 argv[<span class="hljs-number">0</span>], 4197 &DatabaseHandleTypeTag, 4198 &is_db_handle); 4199 <span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4200 4201 <span class="hljs-comment">// Throw a `TypeError` if it doesn't.</span> 4202 <span class="hljs-keyword">if</span> (!is_db_handle) { 4203 <span class="hljs-comment">// Throw a TypeError.</span> 4204 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4205 } 4206}</code></pre> 4207<h4>napi_define_class<span><a class="mark" href="#n_api_napi_define_class" id="n_api_napi_define_class">#</a></span></h4> 4208<div class="api_metadata"> 4209<span>Added in: v8.0.0</span> 4210<span>N-API version: 1</span> 4211</div> 4212<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_define_class</span><span class="hljs-params">(napi_env env, 4213 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* utf8name, 4214 <span class="hljs-type">size_t</span> length, 4215 napi_callback constructor, 4216 <span class="hljs-type">void</span>* data, 4217 <span class="hljs-type">size_t</span> property_count, 4218 <span class="hljs-keyword">const</span> napi_property_descriptor* properties, 4219 napi_value* result)</span>;</code></pre> 4220<ul> 4221<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4222<li><code>[in] utf8name</code>: Name of the JavaScript constructor function; When wrapping a 4223C++ class, we recommend for clarity that this name be the same as that of 4224the C++ class.</li> 4225<li><code>[in] length</code>: The length of the <code>utf8name</code> in bytes, or <code>NAPI_AUTO_LENGTH</code> 4226if it is null-terminated.</li> 4227<li><code>[in] constructor</code>: Callback function that handles constructing instances 4228of the class. When wrapping a C++ class, this method must be a static member 4229with the <a href="#n_api_napi_callback"><code>napi_callback</code></a> signature. A C++ class constructor cannot be 4230used. <a href="#n_api_napi_callback"><code>napi_callback</code></a> provides more details.</li> 4231<li><code>[in] data</code>: Optional data to be passed to the constructor callback as 4232the <code>data</code> property of the callback info.</li> 4233<li><code>[in] property_count</code>: Number of items in the <code>properties</code> array argument.</li> 4234<li><code>[in] properties</code>: Array of property descriptors describing static and 4235instance data properties, accessors, and methods on the class 4236See <code>napi_property_descriptor</code>.</li> 4237<li><code>[out] result</code>: A <code>napi_value</code> representing the constructor function for 4238the class.</li> 4239</ul> 4240<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4241<p>Defines a JavaScript class, including:</p> 4242<ul> 4243<li>A JavaScript constructor function that has the class name. When wrapping a 4244corresponding C++ class, the callback passed via <code>constructor</code> can be used to 4245instantiate a new C++ class instance, which can then be placed inside the 4246JavaScript object instance being constructed using <a href="#n_api_napi_wrap"><code>napi_wrap</code></a>.</li> 4247<li>Properties on the constructor function whose implementation can call 4248corresponding <em>static</em> data properties, accessors, and methods of the C++ 4249class (defined by property descriptors with the <code>napi_static</code> attribute).</li> 4250<li>Properties on the constructor function's <code>prototype</code> object. When wrapping a 4251C++ class, <em>non-static</em> data properties, accessors, and methods of the C++ 4252class can be called from the static functions given in the property 4253descriptors without the <code>napi_static</code> attribute after retrieving the C++ class 4254instance placed inside the JavaScript object instance by using 4255<a href="#n_api_napi_unwrap"><code>napi_unwrap</code></a>.</li> 4256</ul> 4257<p>When wrapping a C++ class, the C++ constructor callback passed via <code>constructor</code> 4258should be a static method on the class that calls the actual class constructor, 4259then wraps the new C++ instance in a JavaScript object, and returns the wrapper 4260object. See <a href="#n_api_napi_wrap"><code>napi_wrap</code></a> for details.</p> 4261<p>The JavaScript constructor function returned from <a href="#n_api_napi_define_class"><code>napi_define_class</code></a> is 4262often saved and used later to construct new instances of the class from native 4263code, and/or to check whether provided values are instances of the class. In 4264that case, to prevent the function value from being garbage-collected, a 4265strong persistent reference to it can be created using 4266<a href="#n_api_napi_create_reference"><code>napi_create_reference</code></a>, ensuring that the reference count is kept >= 1.</p> 4267<p>Any non-<code>NULL</code> data which is passed to this API via the <code>data</code> parameter or via 4268the <code>data</code> field of the <code>napi_property_descriptor</code> array items can be associated 4269with the resulting JavaScript constructor (which is returned in the <code>result</code> 4270parameter) and freed whenever the class is garbage-collected by passing both 4271the JavaScript function and the data to <a href="#n_api_napi_add_finalizer"><code>napi_add_finalizer</code></a>.</p> 4272<h4>napi_wrap<span><a class="mark" href="#n_api_napi_wrap" id="n_api_napi_wrap">#</a></span></h4> 4273<div class="api_metadata"> 4274<span>Added in: v8.0.0</span> 4275<span>N-API version: 1</span> 4276</div> 4277<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_wrap</span><span class="hljs-params">(napi_env env, 4278 napi_value js_object, 4279 <span class="hljs-type">void</span>* native_object, 4280 napi_finalize finalize_cb, 4281 <span class="hljs-type">void</span>* finalize_hint, 4282 napi_ref* result)</span>;</code></pre> 4283<ul> 4284<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4285<li><code>[in] js_object</code>: The JavaScript object that will be the wrapper for the 4286native object.</li> 4287<li><code>[in] native_object</code>: The native instance that will be wrapped in the 4288JavaScript object.</li> 4289<li><code>[in] finalize_cb</code>: Optional native callback that can be used to free the 4290native instance when the JavaScript object is ready for garbage-collection. 4291<a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 4292<li><code>[in] finalize_hint</code>: Optional contextual hint that is passed to the 4293finalize callback.</li> 4294<li><code>[out] result</code>: Optional reference to the wrapped object.</li> 4295</ul> 4296<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4297<p>Wraps a native instance in a JavaScript object. The native instance can be 4298retrieved later using <code>napi_unwrap()</code>.</p> 4299<p>When JavaScript code invokes a constructor for a class that was defined using 4300<code>napi_define_class()</code>, the <code>napi_callback</code> for the constructor is invoked. 4301After constructing an instance of the native class, the callback must then call 4302<code>napi_wrap()</code> to wrap the newly constructed instance in the already-created 4303JavaScript object that is the <code>this</code> argument to the constructor callback. 4304(That <code>this</code> object was created from the constructor function's <code>prototype</code>, 4305so it already has definitions of all the instance properties and methods.)</p> 4306<p>Typically when wrapping a class instance, a finalize callback should be 4307provided that simply deletes the native instance that is received as the <code>data</code> 4308argument to the finalize callback.</p> 4309<p>The optional returned reference is initially a weak reference, meaning it 4310has a reference count of 0. Typically this reference count would be incremented 4311temporarily during async operations that require the instance to remain valid.</p> 4312<p><em>Caution</em>: The optional returned reference (if obtained) should be deleted via 4313<a href="#n_api_napi_delete_reference"><code>napi_delete_reference</code></a> ONLY in response to the finalize callback 4314invocation. If it is deleted before then, then the finalize callback may never 4315be invoked. Therefore, when obtaining a reference a finalize callback is also 4316required in order to enable correct disposal of the reference.</p> 4317<p>Calling <code>napi_wrap()</code> a second time on an object will return an error. To 4318associate another native instance with the object, use <code>napi_remove_wrap()</code> 4319first.</p> 4320<h4>napi_unwrap<span><a class="mark" href="#n_api_napi_unwrap" id="n_api_napi_unwrap">#</a></span></h4> 4321<div class="api_metadata"> 4322<span>Added in: v8.0.0</span> 4323<span>N-API version: 1</span> 4324</div> 4325<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_unwrap</span><span class="hljs-params">(napi_env env, 4326 napi_value js_object, 4327 <span class="hljs-type">void</span>** result)</span>;</code></pre> 4328<ul> 4329<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4330<li><code>[in] js_object</code>: The object associated with the native instance.</li> 4331<li><code>[out] result</code>: Pointer to the wrapped native instance.</li> 4332</ul> 4333<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4334<p>Retrieves a native instance that was previously wrapped in a JavaScript 4335object using <code>napi_wrap()</code>.</p> 4336<p>When JavaScript code invokes a method or property accessor on the class, the 4337corresponding <code>napi_callback</code> is invoked. If the callback is for an instance 4338method or accessor, then the <code>this</code> argument to the callback is the wrapper 4339object; the wrapped C++ instance that is the target of the call can be obtained 4340then by calling <code>napi_unwrap()</code> on the wrapper object.</p> 4341<h4>napi_remove_wrap<span><a class="mark" href="#n_api_napi_remove_wrap" id="n_api_napi_remove_wrap">#</a></span></h4> 4342<div class="api_metadata"> 4343<span>Added in: v8.5.0</span> 4344<span>N-API version: 1</span> 4345</div> 4346<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_remove_wrap</span><span class="hljs-params">(napi_env env, 4347 napi_value js_object, 4348 <span class="hljs-type">void</span>** result)</span>;</code></pre> 4349<ul> 4350<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4351<li><code>[in] js_object</code>: The object associated with the native instance.</li> 4352<li><code>[out] result</code>: Pointer to the wrapped native instance.</li> 4353</ul> 4354<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4355<p>Retrieves a native instance that was previously wrapped in the JavaScript 4356object <code>js_object</code> using <code>napi_wrap()</code> and removes the wrapping. If a finalize 4357callback was associated with the wrapping, it will no longer be called when the 4358JavaScript object becomes garbage-collected.</p> 4359<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> 4360<div class="api_metadata"> 4361<span>Added in: v14.8.0, v12.19.0</span> 4362<span>N-API version: 8</span> 4363</div> 4364<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_type_tag_object</span><span class="hljs-params">(napi_env env, 4365 napi_value js_object, 4366 <span class="hljs-keyword">const</span> napi_type_tag* type_tag)</span>;</code></pre> 4367<ul> 4368<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4369<li><code>[in] js_object</code>: The JavaScript object to be marked.</li> 4370<li><code>[in] type_tag</code>: The tag with which the object is to be marked.</li> 4371</ul> 4372<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4373<p>Associates the value of the <code>type_tag</code> pointer with the JavaScript object. 4374<code>napi_check_object_type_tag()</code> can then be used to compare the tag that was 4375attached to the object with one owned by the addon to ensure that the object 4376has the right type.</p> 4377<p>If the object already has an associated type tag, this API will return 4378<code>napi_invalid_arg</code>.</p> 4379<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> 4380<div class="api_metadata"> 4381<span>Added in: v14.8.0, v12.19.0</span> 4382<span>N-API version: 8</span> 4383</div> 4384<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, 4385 napi_value js_object, 4386 <span class="hljs-keyword">const</span> napi_type_tag* type_tag, 4387 <span class="hljs-type">bool</span>* result)</span>;</code></pre> 4388<ul> 4389<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4390<li><code>[in] js_object</code>: The JavaScript object whose type tag to examine.</li> 4391<li><code>[in] type_tag</code>: The tag with which to compare any tag found on the object.</li> 4392<li><code>[out] result</code>: Whether the type tag given matched the type tag on the 4393object. <code>false</code> is also returned if no type tag was found on the object.</li> 4394</ul> 4395<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4396<p>Compares the pointer given as <code>type_tag</code> with any that can be found on 4397<code>js_object</code>. If no tag is found on <code>js_object</code> or, if a tag is found but it does 4398not match <code>type_tag</code>, then <code>result</code> is set to <code>false</code>. If a tag is found and it 4399matches <code>type_tag</code>, then <code>result</code> is set to <code>true</code>.</p> 4400<h4>napi_add_finalizer<span><a class="mark" href="#n_api_napi_add_finalizer" id="n_api_napi_add_finalizer">#</a></span></h4> 4401<div class="api_metadata"> 4402<span>Added in: v8.0.0</span> 4403<span>N-API version: 5</span> 4404</div> 4405<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_add_finalizer</span><span class="hljs-params">(napi_env env, 4406 napi_value js_object, 4407 <span class="hljs-type">void</span>* native_object, 4408 napi_finalize finalize_cb, 4409 <span class="hljs-type">void</span>* finalize_hint, 4410 napi_ref* result)</span>;</code></pre> 4411<ul> 4412<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4413<li><code>[in] js_object</code>: The JavaScript object to which the native data will be 4414attached.</li> 4415<li><code>[in] native_object</code>: The native data that will be attached to the JavaScript 4416object.</li> 4417<li><code>[in] finalize_cb</code>: Native callback that will be used to free the 4418native data when the JavaScript object is ready for garbage-collection. 4419<a href="#n_api_napi_finalize"><code>napi_finalize</code></a> provides more details.</li> 4420<li><code>[in] finalize_hint</code>: Optional contextual hint that is passed to the 4421finalize callback.</li> 4422<li><code>[out] result</code>: Optional reference to the JavaScript object.</li> 4423</ul> 4424<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4425<p>Adds a <code>napi_finalize</code> callback which will be called when the JavaScript object 4426in <code>js_object</code> is ready for garbage collection. This API is similar to 4427<code>napi_wrap()</code> except that:</p> 4428<ul> 4429<li>the native data cannot be retrieved later using <code>napi_unwrap()</code>,</li> 4430<li>nor can it be removed later using <code>napi_remove_wrap()</code>, and</li> 4431<li>the API can be called multiple times with different data items in order to 4432attach each of them to the JavaScript object, and</li> 4433<li>the object manipulated by the API can be used with <code>napi_wrap()</code>.</li> 4434</ul> 4435<p><em>Caution</em>: The optional returned reference (if obtained) should be deleted via 4436<a href="#n_api_napi_delete_reference"><code>napi_delete_reference</code></a> ONLY in response to the finalize callback 4437invocation. If it is deleted before then, then the finalize callback may never 4438be invoked. Therefore, when obtaining a reference a finalize callback is also 4439required in order to enable correct disposal of the reference.</p> 4440</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> 4441<p>Addon modules often need to leverage async helpers from libuv as part of their 4442implementation. This allows them to schedule work to be executed asynchronously 4443so that their methods can return in advance of the work being completed. This 4444allows them to avoid blocking overall execution of the Node.js application.</p> 4445<p>Node-API provides an ABI-stable interface for these 4446supporting functions which covers the most common asynchronous use cases.</p> 4447<p>Node-API defines the <code>napi_async_work</code> structure which is used to manage 4448asynchronous workers. Instances are created/deleted with 4449<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> 4450<p>The <code>execute</code> and <code>complete</code> callbacks are functions that will be 4451invoked when the executor is ready to execute and when it completes its 4452task respectively.</p> 4453<p>The <code>execute</code> function should avoid making any Node-API calls 4454that could result in the execution of JavaScript or interaction with 4455JavaScript objects. Most often, any code that needs to make Node-API 4456calls should be made in <code>complete</code> callback instead. 4457Avoid using the <code>napi_env</code> parameter in the execute callback as 4458it will likely execute JavaScript.</p> 4459<p>These functions implement the following interfaces:</p> 4460<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, 4461 <span class="hljs-type">void</span>* data)</span>; 4462<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, 4463 napi_status status, 4464 <span class="hljs-type">void</span>* data)</span>;</code></pre> 4465<p>When these methods are invoked, the <code>data</code> parameter passed will be the 4466addon-provided <code>void*</code> data that was passed into the 4467<code>napi_create_async_work</code> call.</p> 4468<p>Once created the async worker can be queued 4469for execution using the <a href="#n_api_napi_queue_async_work"><code>napi_queue_async_work</code></a> function:</p> 4470<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_queue_async_work</span><span class="hljs-params">(napi_env env, 4471 napi_async_work work)</span>;</code></pre> 4472<p><a href="#n_api_napi_cancel_async_work"><code>napi_cancel_async_work</code></a> can be used if the work needs 4473to be cancelled before the work has started execution.</p> 4474<p>After calling <a href="#n_api_napi_cancel_async_work"><code>napi_cancel_async_work</code></a>, the <code>complete</code> callback 4475will be invoked with a status value of <code>napi_cancelled</code>. 4476The work should not be deleted before the <code>complete</code> 4477callback invocation, even when it was cancelled.</p> 4478<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> 4479<div class="api_metadata"> 4480<details class="changelog"><summary>History</summary> 4481<table> 4482<tbody><tr><th>Version</th><th>Changes</th></tr> 4483<tr><td>v8.6.0</td> 4484<td><p>Added <code>async_resource</code> and <code>async_resource_name</code> parameters.</p></td></tr> 4485<tr><td>v8.0.0</td> 4486<td><p><span>Added in: v8.0.0</span></p></td></tr> 4487</tbody></table> 4488</details> 4489<span>N-API version: 1</span> 4490</div> 4491<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_async_work</span><span class="hljs-params">(napi_env env, 4492 napi_value async_resource, 4493 napi_value async_resource_name, 4494 napi_async_execute_callback execute, 4495 napi_async_complete_callback complete, 4496 <span class="hljs-type">void</span>* data, 4497 napi_async_work* result)</span>;</code></pre> 4498<ul> 4499<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4500<li><code>[in] async_resource</code>: An optional object associated with the async work 4501that 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> 4502<li><code>[in] async_resource_name</code>: Identifier for the kind of resource that is being 4503provided for diagnostic information exposed by the <code>async_hooks</code> API.</li> 4504<li><code>[in] execute</code>: The native function which should be called to execute the 4505logic asynchronously. The given function is called from a worker pool thread 4506and can execute in parallel with the main event loop thread.</li> 4507<li><code>[in] complete</code>: The native function which will be called when the 4508asynchronous logic is completed or is cancelled. The given function is called 4509from the main event loop thread. <a href="#n_api_napi_async_complete_callback"><code>napi_async_complete_callback</code></a> provides 4510more details.</li> 4511<li><code>[in] data</code>: User-provided data context. This will be passed back into the 4512execute and complete functions.</li> 4513<li><code>[out] result</code>: <code>napi_async_work*</code> which is the handle to the newly created 4514async work.</li> 4515</ul> 4516<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4517<p>This API allocates a work object that is used to execute logic asynchronously. 4518It 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 4519required.</p> 4520<p><code>async_resource_name</code> should be a null-terminated, UTF-8-encoded string.</p> 4521<p>The <code>async_resource_name</code> identifier is provided by the user and should be 4522representative of the type of async work being performed. It is also recommended 4523to apply namespacing to the identifier, e.g. by including the module name. See 4524the <a href="async_hooks.html#async_hooks_type"><code>async_hooks</code> documentation</a> for more information.</p> 4525<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> 4526<div class="api_metadata"> 4527<span>Added in: v8.0.0</span> 4528<span>N-API version: 1</span> 4529</div> 4530<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_delete_async_work</span><span class="hljs-params">(napi_env env, 4531 napi_async_work work)</span>;</code></pre> 4532<ul> 4533<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4534<li><code>[in] work</code>: The handle returned by the call to <code>napi_create_async_work</code>.</li> 4535</ul> 4536<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4537<p>This API frees a previously allocated work object.</p> 4538<p>This API can be called even if there is a pending JavaScript exception.</p> 4539<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> 4540<div class="api_metadata"> 4541<span>Added in: v8.0.0</span> 4542<span>N-API version: 1</span> 4543</div> 4544<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_queue_async_work</span><span class="hljs-params">(napi_env env, 4545 napi_async_work work)</span>;</code></pre> 4546<ul> 4547<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4548<li><code>[in] work</code>: The handle returned by the call to <code>napi_create_async_work</code>.</li> 4549</ul> 4550<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4551<p>This API requests that the previously allocated work be scheduled 4552for execution. Once it returns successfully, this API must not be called again 4553with the same <code>napi_async_work</code> item or the result will be undefined.</p> 4554<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> 4555<div class="api_metadata"> 4556<span>Added in: v8.0.0</span> 4557<span>N-API version: 1</span> 4558</div> 4559<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_cancel_async_work</span><span class="hljs-params">(napi_env env, 4560 napi_async_work work)</span>;</code></pre> 4561<ul> 4562<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4563<li><code>[in] work</code>: The handle returned by the call to <code>napi_create_async_work</code>.</li> 4564</ul> 4565<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4566<p>This API cancels queued work if it has not yet 4567been started. If it has already started executing, it cannot be 4568cancelled and <code>napi_generic_failure</code> will be returned. If successful, 4569the <code>complete</code> callback will be invoked with a status value of 4570<code>napi_cancelled</code>. The work should not be deleted before the <code>complete</code> 4571callback invocation, even if it has been successfully cancelled.</p> 4572<p>This API can be called even if there is a pending JavaScript exception.</p> 4573</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> 4574<p>The simple asynchronous work APIs above may not be appropriate for every 4575scenario. When using any other asynchronous mechanism, the following APIs 4576are necessary to ensure an asynchronous operation is properly tracked by 4577the runtime.</p> 4578<h4>napi_async_init<span><a class="mark" href="#n_api_napi_async_init" id="n_api_napi_async_init">#</a></span></h4> 4579<div class="api_metadata"> 4580<span>Added in: v8.6.0</span> 4581<span>N-API version: 1</span> 4582</div> 4583<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_async_init</span><span class="hljs-params">(napi_env env, 4584 napi_value async_resource, 4585 napi_value async_resource_name, 4586 napi_async_context* result)</span></code></pre> 4587<ul> 4588<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4589<li><code>[in] async_resource</code>: Object associated with the async work 4590that 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 4591accessed by <a href="async_hooks.html#async_hooks_async_hooks_executionasyncresource"><code>async_hooks.executionAsyncResource()</code></a>.</li> 4592<li><code>[in] async_resource_name</code>: Identifier for the kind of resource that is being 4593provided for diagnostic information exposed by the <code>async_hooks</code> API.</li> 4594<li><code>[out] result</code>: The initialized async context.</li> 4595</ul> 4596<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4597<p>The <code>async_resource</code> object needs to be kept alive until 4598<a href="#n_api_napi_async_destroy"><code>napi_async_destroy</code></a> to keep <code>async_hooks</code> related API acts correctly. In 4599order to retain ABI compatibility with previous versions, <code>napi_async_context</code>s 4600are not maintaining the strong reference to the <code>async_resource</code> objects to 4601avoid introducing causing memory leaks. However, if the <code>async_resource</code> is 4602garbage collected by JavaScript engine before the <code>napi_async_context</code> was 4603destroyed by <code>napi_async_destroy</code>, calling <code>napi_async_context</code> related APIs 4604like <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 4605problems like loss of async context when using the <code>AsyncLocalStoage</code> API.</p> 4606<p>In order to retain ABI compatibility with previous versions, passing <code>NULL</code> 4607for <code>async_resource</code> does not result in an error. However, this is not 4608recommended as this will result poor results with <code>async_hooks</code> 4609<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 4610now required by the underlying <code>async_hooks</code> implementation in order to provide 4611the linkage between async callbacks.</p> 4612<h4>napi_async_destroy<span><a class="mark" href="#n_api_napi_async_destroy" id="n_api_napi_async_destroy">#</a></span></h4> 4613<div class="api_metadata"> 4614<span>Added in: v8.6.0</span> 4615<span>N-API version: 1</span> 4616</div> 4617<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_async_destroy</span><span class="hljs-params">(napi_env env, 4618 napi_async_context async_context)</span>;</code></pre> 4619<ul> 4620<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4621<li><code>[in] async_context</code>: The async context to be destroyed.</li> 4622</ul> 4623<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4624<p>This API can be called even if there is a pending JavaScript exception.</p> 4625<h4>napi_make_callback<span><a class="mark" href="#n_api_napi_make_callback" id="n_api_napi_make_callback">#</a></span></h4> 4626<div class="api_metadata"> 4627<details class="changelog"><summary>History</summary> 4628<table> 4629<tbody><tr><th>Version</th><th>Changes</th></tr> 4630<tr><td>v8.6.0</td> 4631<td><p>Added <code>async_context</code> parameter.</p></td></tr> 4632<tr><td>v8.0.0</td> 4633<td><p><span>Added in: v8.0.0</span></p></td></tr> 4634</tbody></table> 4635</details> 4636<span>N-API version: 1</span> 4637</div> 4638<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, 4639 napi_async_context async_context, 4640 napi_value recv, 4641 napi_value func, 4642 <span class="hljs-type">size_t</span> argc, 4643 <span class="hljs-keyword">const</span> napi_value* argv, 4644 napi_value* result)</span>;</code></pre> 4645<ul> 4646<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4647<li><code>[in] async_context</code>: Context for the async operation that is 4648invoking the callback. This should normally be a value previously 4649obtained from <a href="#n_api_napi_async_init"><code>napi_async_init</code></a>. 4650In order to retain ABI compatibility with previous versions, passing <code>NULL</code> 4651for <code>async_context</code> does not result in an error. However, this results 4652in incorrect operation of async hooks. Potential issues include loss of 4653async context when using the <code>AsyncLocalStorage</code> API.</li> 4654<li><code>[in] recv</code>: The <code>this</code> value passed to the called function.</li> 4655<li><code>[in] func</code>: <code>napi_value</code> representing the JavaScript function to be invoked.</li> 4656<li><code>[in] argc</code>: The count of elements in the <code>argv</code> array.</li> 4657<li><code>[in] argv</code>: Array of JavaScript values as <code>napi_value</code> representing the 4658arguments to the function.</li> 4659<li><code>[out] result</code>: <code>napi_value</code> representing the JavaScript object returned.</li> 4660</ul> 4661<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4662<p>This method allows a JavaScript function object to be called from a native 4663add-on. This API is similar to <code>napi_call_function</code>. However, it is used to call 4664<em>from</em> native code back <em>into</em> JavaScript <em>after</em> returning from an async 4665operation (when there is no other script on the stack). It is a fairly simple 4666wrapper around <code>node::MakeCallback</code>.</p> 4667<p>Note it is <em>not</em> necessary to use <code>napi_make_callback</code> from within a 4668<code>napi_async_complete_callback</code>; in that situation the callback's async 4669context has already been set up, so a direct call to <code>napi_call_function</code> 4670is sufficient and appropriate. Use of the <code>napi_make_callback</code> function 4671may be required when implementing custom async behavior that does not use 4672<code>napi_create_async_work</code>.</p> 4673<p>Any <code>process.nextTick</code>s or Promises scheduled on the microtask queue by 4674JavaScript during the callback are ran before returning back to C/C++.</p> 4675<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> 4676<div class="api_metadata"> 4677<span>Added in: v9.6.0</span> 4678<span>N-API version: 3</span> 4679</div> 4680<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, 4681 napi_value resource_object, 4682 napi_async_context context, 4683 napi_callback_scope* result)</span></code></pre> 4684<ul> 4685<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4686<li><code>[in] resource_object</code>: An object associated with the async work 4687that 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 4688parameter has been deprecated and is ignored at runtime. Use the 4689<code>async_resource</code> parameter in <a href="#n_api_napi_async_init"><code>napi_async_init</code></a> instead.</li> 4690<li><code>[in] context</code>: Context for the async operation that is invoking the callback. 4691This should be a value previously obtained from <a href="#n_api_napi_async_init"><code>napi_async_init</code></a>.</li> 4692<li><code>[out] result</code>: The newly created scope.</li> 4693</ul> 4694<p>There are cases (for example, resolving promises) where it is 4695necessary to have the equivalent of the scope associated with a callback 4696in place when making certain Node-API calls. If there is no other script on 4697the stack the <a href="#n_api_napi_open_callback_scope"><code>napi_open_callback_scope</code></a> and 4698<a href="#n_api_napi_close_callback_scope"><code>napi_close_callback_scope</code></a> functions can be used to open/close 4699the required scope.</p> 4700<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> 4701<div class="api_metadata"> 4702<span>Added in: v9.6.0</span> 4703<span>N-API version: 3</span> 4704</div> 4705<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, 4706 napi_callback_scope scope)</span></code></pre> 4707<ul> 4708<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4709<li><code>[in] scope</code>: The scope to be closed.</li> 4710</ul> 4711<p>This API can be called even if there is a pending JavaScript exception.</p> 4712</section><section><h3>Version management<span><a class="mark" href="#n_api_version_management" id="n_api_version_management">#</a></span></h3> 4713<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> 4714<div class="api_metadata"> 4715<span>Added in: v8.4.0</span> 4716<span>N-API version: 1</span> 4717</div> 4718<pre><code class="language-c"><span class="hljs-keyword">typedef</span> <span class="hljs-class"><span class="hljs-keyword">struct</span> {</span> 4719 <span class="hljs-type">uint32_t</span> major; 4720 <span class="hljs-type">uint32_t</span> minor; 4721 <span class="hljs-type">uint32_t</span> patch; 4722 <span class="hljs-keyword">const</span> <span class="hljs-type">char</span>* release; 4723} napi_node_version; 4724 4725napi_status <span class="hljs-title function_">napi_get_node_version</span><span class="hljs-params">(napi_env env, 4726 <span class="hljs-keyword">const</span> napi_node_version** version)</span>;</code></pre> 4727<ul> 4728<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4729<li><code>[out] version</code>: A pointer to version information for Node.js itself.</li> 4730</ul> 4731<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4732<p>This function fills the <code>version</code> struct with the major, minor, and patch 4733version of Node.js that is currently running, and the <code>release</code> field with the 4734value of <a href="process.html#process_process_release"><code>process.release.name</code></a>.</p> 4735<p>The returned buffer is statically allocated and does not need to be freed.</p> 4736<h4>napi_get_version<span><a class="mark" href="#n_api_napi_get_version" id="n_api_napi_get_version">#</a></span></h4> 4737<div class="api_metadata"> 4738<span>Added in: v8.0.0</span> 4739<span>N-API version: 1</span> 4740</div> 4741<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_get_version</span><span class="hljs-params">(napi_env env, 4742 <span class="hljs-type">uint32_t</span>* result)</span>;</code></pre> 4743<ul> 4744<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4745<li><code>[out] result</code>: The highest version of Node-API supported.</li> 4746</ul> 4747<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4748<p>This API returns the highest Node-API version supported by the 4749Node.js runtime. Node-API is planned to be additive such that 4750newer releases of Node.js may support additional API functions. 4751In order to allow an addon to use a newer function when running with 4752versions of Node.js that support it, while providing 4753fallback behavior when running with Node.js versions that don't 4754support it:</p> 4755<ul> 4756<li>Call <code>napi_get_version()</code> to determine if the API is available.</li> 4757<li>If available, dynamically load a pointer to the function using <code>uv_dlsym()</code>.</li> 4758<li>Use the dynamically loaded pointer to invoke the function.</li> 4759<li>If the function is not available, provide an alternate implementation 4760that does not use the function.</li> 4761</ul> 4762</section><section><h3>Memory management<span><a class="mark" href="#n_api_memory_management" id="n_api_memory_management">#</a></span></h3> 4763<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> 4764<div class="api_metadata"> 4765<span>Added in: v8.5.0</span> 4766<span>N-API version: 1</span> 4767</div> 4768<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, 4769 <span class="hljs-type">int64_t</span> change_in_bytes, 4770 <span class="hljs-type">int64_t</span>* result)</span>;</code></pre> 4771<ul> 4772<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4773<li><code>[in] change_in_bytes</code>: The change in externally allocated memory that is kept 4774alive by JavaScript objects.</li> 4775<li><code>[out] result</code>: The adjusted value</li> 4776</ul> 4777<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4778<p>This function gives V8 an indication of the amount of externally allocated 4779memory that is kept alive by JavaScript objects (i.e. a JavaScript object 4780that points to its own memory allocated by a native module). Registering 4781externally allocated memory will trigger global garbage collections more 4782often than it would otherwise.</p> 4783</section><section><h3>Promises<span><a class="mark" href="#n_api_promises" id="n_api_promises">#</a></span></h3> 4784<p>Node-API provides facilities for creating <code>Promise</code> objects as described in 4785<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 4786objects. When a promise is created by <code>napi_create_promise()</code>, a "deferred" 4787object is created and returned alongside the <code>Promise</code>. The deferred object is 4788bound to the created <code>Promise</code> and is the only means to resolve or reject the 4789<code>Promise</code> using <code>napi_resolve_deferred()</code> or <code>napi_reject_deferred()</code>. The 4790deferred object that is created by <code>napi_create_promise()</code> is freed by 4791<code>napi_resolve_deferred()</code> or <code>napi_reject_deferred()</code>. The <code>Promise</code> object may 4792be returned to JavaScript where it can be used in the usual fashion.</p> 4793<p>For example, to create a promise and pass it to an asynchronous worker:</p> 4794<pre><code class="language-c">napi_deferred deferred; 4795napi_value promise; 4796napi_status status; 4797 4798<span class="hljs-comment">// Create the promise.</span> 4799status = napi_create_promise(env, &deferred, &promise); 4800<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4801 4802<span class="hljs-comment">// Pass the deferred to a function that performs an asynchronous action.</span> 4803do_something_asynchronous(deferred); 4804 4805<span class="hljs-comment">// Return the promise to JS</span> 4806<span class="hljs-keyword">return</span> promise;</code></pre> 4807<p>The above function <code>do_something_asynchronous()</code> would perform its asynchronous 4808action and then it would resolve or reject the deferred, thereby concluding the 4809promise and freeing the deferred:</p> 4810<pre><code class="language-c">napi_deferred deferred; 4811napi_value undefined; 4812napi_status status; 4813 4814<span class="hljs-comment">// Create a value with which to conclude the deferred.</span> 4815status = napi_get_undefined(env, &undefined); 4816<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4817 4818<span class="hljs-comment">// Resolve or reject the promise associated with the deferred depending on</span> 4819<span class="hljs-comment">// whether the asynchronous action succeeded.</span> 4820<span class="hljs-keyword">if</span> (asynchronous_action_succeeded) { 4821 status = napi_resolve_deferred(env, deferred, undefined); 4822} <span class="hljs-keyword">else</span> { 4823 status = napi_reject_deferred(env, deferred, undefined); 4824} 4825<span class="hljs-keyword">if</span> (status != napi_ok) <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 4826 4827<span class="hljs-comment">// At this point the deferred has been freed, so we should assign NULL to it.</span> 4828deferred = <span class="hljs-literal">NULL</span>;</code></pre> 4829<h4>napi_create_promise<span><a class="mark" href="#n_api_napi_create_promise" id="n_api_napi_create_promise">#</a></span></h4> 4830<div class="api_metadata"> 4831<span>Added in: v8.5.0</span> 4832<span>N-API version: 1</span> 4833</div> 4834<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_create_promise</span><span class="hljs-params">(napi_env env, 4835 napi_deferred* deferred, 4836 napi_value* promise)</span>;</code></pre> 4837<ul> 4838<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4839<li><code>[out] deferred</code>: A newly created deferred object which can later be passed to 4840<code>napi_resolve_deferred()</code> or <code>napi_reject_deferred()</code> to resolve resp. reject 4841the associated promise.</li> 4842<li><code>[out] promise</code>: The JavaScript promise associated with the deferred object.</li> 4843</ul> 4844<p>Returns <code>napi_ok</code> if the API succeeded.</p> 4845<p>This API creates a deferred object and a JavaScript promise.</p> 4846<h4>napi_resolve_deferred<span><a class="mark" href="#n_api_napi_resolve_deferred" id="n_api_napi_resolve_deferred">#</a></span></h4> 4847<div class="api_metadata"> 4848<span>Added in: v8.5.0</span> 4849<span>N-API version: 1</span> 4850</div> 4851<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_resolve_deferred</span><span class="hljs-params">(napi_env env, 4852 napi_deferred deferred, 4853 napi_value resolution)</span>;</code></pre> 4854<ul> 4855<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4856<li><code>[in] deferred</code>: The deferred object whose associated promise to resolve.</li> 4857<li><code>[in] resolution</code>: The value with which to resolve the promise.</li> 4858</ul> 4859<p>This API resolves a JavaScript promise by way of the deferred object 4860with which it is associated. Thus, it can only be used to resolve JavaScript 4861promises for which the corresponding deferred object is available. This 4862effectively means that the promise must have been created using 4863<code>napi_create_promise()</code> and the deferred object returned from that call must 4864have been retained in order to be passed to this API.</p> 4865<p>The deferred object is freed upon successful completion.</p> 4866<h4>napi_reject_deferred<span><a class="mark" href="#n_api_napi_reject_deferred" id="n_api_napi_reject_deferred">#</a></span></h4> 4867<div class="api_metadata"> 4868<span>Added in: v8.5.0</span> 4869<span>N-API version: 1</span> 4870</div> 4871<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_reject_deferred</span><span class="hljs-params">(napi_env env, 4872 napi_deferred deferred, 4873 napi_value rejection)</span>;</code></pre> 4874<ul> 4875<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4876<li><code>[in] deferred</code>: The deferred object whose associated promise to resolve.</li> 4877<li><code>[in] rejection</code>: The value with which to reject the promise.</li> 4878</ul> 4879<p>This API rejects a JavaScript promise by way of the deferred object 4880with which it is associated. Thus, it can only be used to reject JavaScript 4881promises for which the corresponding deferred object is available. This 4882effectively means that the promise must have been created using 4883<code>napi_create_promise()</code> and the deferred object returned from that call must 4884have been retained in order to be passed to this API.</p> 4885<p>The deferred object is freed upon successful completion.</p> 4886<h4>napi_is_promise<span><a class="mark" href="#n_api_napi_is_promise" id="n_api_napi_is_promise">#</a></span></h4> 4887<div class="api_metadata"> 4888<span>Added in: v8.5.0</span> 4889<span>N-API version: 1</span> 4890</div> 4891<pre><code class="language-c">napi_status <span class="hljs-title function_">napi_is_promise</span><span class="hljs-params">(napi_env env, 4892 napi_value value, 4893 <span class="hljs-type">bool</span>* is_promise)</span>;</code></pre> 4894<ul> 4895<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4896<li><code>[in] value</code>: The value to examine</li> 4897<li><code>[out] is_promise</code>: Flag indicating whether <code>promise</code> is a native promise 4898object (that is, a promise object created by the underlying engine).</li> 4899</ul> 4900</section><section><h3>Script execution<span><a class="mark" href="#n_api_script_execution" id="n_api_script_execution">#</a></span></h3> 4901<p>Node-API provides an API for executing a string containing JavaScript using the 4902underlying JavaScript engine.</p> 4903<h4>napi_run_script<span><a class="mark" href="#n_api_napi_run_script" id="n_api_napi_run_script">#</a></span></h4> 4904<div class="api_metadata"> 4905<span>Added in: v8.5.0</span> 4906<span>N-API version: 1</span> 4907</div> 4908<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, 4909 napi_value script, 4910 napi_value* result)</span>;</code></pre> 4911<ul> 4912<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4913<li><code>[in] script</code>: A JavaScript string containing the script to execute.</li> 4914<li><code>[out] result</code>: The value resulting from having executed the script.</li> 4915</ul> 4916<p>This function executes a string of JavaScript code and returns its result with 4917the following caveats:</p> 4918<ul> 4919<li>Unlike <code>eval</code>, this function does not allow the script to access the current 4920lexical scope, and therefore also does not allow to access the 4921<a href="modules.html#modules_the_module_scope">module scope</a>, meaning that pseudo-globals such as <code>require</code> will not be 4922available.</li> 4923<li>The script can access the <a href="globals.html">global scope</a>. Function and <code>var</code> declarations 4924in the script will be added to the <a href="globals.html#globals_global"><code>global</code></a> object. Variable declarations 4925made using <code>let</code> and <code>const</code> will be visible globally, but will not be added 4926to the <a href="globals.html#globals_global"><code>global</code></a> object.</li> 4927<li>The value of <code>this</code> is <a href="globals.html#globals_global"><code>global</code></a> within the script.</li> 4928</ul> 4929</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> 4930<p>Node-API provides a function for getting the current event loop associated with 4931a specific <code>napi_env</code>.</p> 4932<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> 4933<div class="api_metadata"> 4934<span>Added in: v9.3.0, v8.10.0</span> 4935<span>N-API version: 2</span> 4936</div> 4937<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, 4938 <span class="hljs-keyword">struct</span> uv_loop_s** loop)</span>;</code></pre> 4939<ul> 4940<li><code>[in] env</code>: The environment that the API is invoked under.</li> 4941<li><code>[out] loop</code>: The current libuv loop instance.</li> 4942</ul> 4943</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> 4944<p>JavaScript functions can normally only be called from a native addon's main 4945thread. If an addon creates additional threads, then Node-API functions that 4946require a <code>napi_env</code>, <code>napi_value</code>, or <code>napi_ref</code> must not be called from those 4947threads.</p> 4948<p>When an addon has additional threads and JavaScript functions need to be invoked 4949based on the processing completed by those threads, those threads must 4950communicate with the addon's main thread so that the main thread can invoke the 4951JavaScript function on their behalf. The thread-safe function APIs provide an 4952easy way to do this.</p> 4953<p>These APIs provide the type <code>napi_threadsafe_function</code> as well as APIs to 4954create, destroy, and call objects of this type. 4955<code>napi_create_threadsafe_function()</code> creates a persistent reference to a 4956<code>napi_value</code> that holds a JavaScript function which can be called from multiple 4957threads. The calls happen asynchronously. This means that values with which the 4958JavaScript callback is to be called will be placed in a queue, and, for each 4959value in the queue, a call will eventually be made to the JavaScript function.</p> 4960<p>Upon creation of a <code>napi_threadsafe_function</code> a <code>napi_finalize</code> callback can be 4961provided. This callback will be invoked on the main thread when the thread-safe 4962function is about to be destroyed. It receives the context and the finalize data 4963given during construction, and provides an opportunity for cleaning up after the 4964threads e.g. by calling <code>uv_thread_join()</code>. <strong>Aside from the main loop thread, 4965no threads should be using the thread-safe function after the finalize callback 4966completes.</strong></p> 4967<p>The <code>context</code> given during the call to <code>napi_create_threadsafe_function()</code> can 4968be retrieved from any thread with a call to 4969<code>napi_get_threadsafe_function_context()</code>.</p> 4970<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> 4971<p><code>napi_call_threadsafe_function()</code> can be used for initiating a call into 4972JavaScript. <code>napi_call_threadsafe_function()</code> accepts a parameter which controls 4973whether the API behaves blockingly. If set to <code>napi_tsfn_nonblocking</code>, the API 4974behaves non-blockingly, returning <code>napi_queue_full</code> if the queue was full, 4975preventing data from being successfully added to the queue. If set to 4976<code>napi_tsfn_blocking</code>, the API blocks until space becomes available in the queue. 4977<code>napi_call_threadsafe_function()</code> never blocks if the thread-safe function was 4978created with a maximum queue size of 0.</p> 4979<p><code>napi_call_threadsafe_function()</code> should not be called with <code>napi_tsfn_blocking</code> 4980from a JavaScript thread, because, if the queue is full, it may cause the 4981JavaScript thread to deadlock.</p> 4982<p>The actual call into JavaScript is controlled by the callback given via the 4983<code>call_js_cb</code> parameter. <code>call_js_cb</code> is invoked on the main thread once for each 4984value that was placed into the queue by a successful call to 4985<code>napi_call_threadsafe_function()</code>. If such a callback is not given, a default 4986callback will be used, and the resulting JavaScript call will have no arguments. 4987The <code>call_js_cb</code> callback receives the JavaScript function to call as a 4988<code>napi_value</code> in its parameters, as well as the <code>void*</code> context pointer used when 4989creating the <code>napi_threadsafe_function</code>, and the next data pointer that was 4990created by one of the secondary threads. The callback can then use an API such 4991as <code>napi_call_function()</code> to call into JavaScript.</p> 4992<p>The callback may also be invoked with <code>env</code> and <code>call_js_cb</code> both set to <code>NULL</code> 4993to indicate that calls into JavaScript are no longer possible, while items 4994remain in the queue that may need to be freed. This normally occurs when the 4995Node.js process exits while there is a thread-safe function still active.</p> 4996<p>It is not necessary to call into JavaScript via <code>napi_make_callback()</code> because 4997Node-API runs <code>call_js_cb</code> in a context appropriate for callbacks.</p> 4998<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> 4999<p>Threads can be added to and removed from a <code>napi_threadsafe_function</code> object 5000during its existence. Thus, in addition to specifying an initial number of 5001threads upon creation, <code>napi_acquire_threadsafe_function</code> can be called to 5002indicate that a new thread will start making use of the thread-safe function. 5003Similarly, <code>napi_release_threadsafe_function</code> can be called to indicate that an 5004existing thread will stop making use of the thread-safe function.</p> 5005<p><code>napi_threadsafe_function</code> objects are destroyed when every thread which uses 5006the object has called <code>napi_release_threadsafe_function()</code> or has received a 5007return status of <code>napi_closing</code> in response to a call to 5008<code>napi_call_threadsafe_function</code>. The queue is emptied before the 5009<code>napi_threadsafe_function</code> is destroyed. <code>napi_release_threadsafe_function()</code> 5010should be the last API call made in conjunction with a given 5011<code>napi_threadsafe_function</code>, because after the call completes, there is no 5012guarantee that the <code>napi_threadsafe_function</code> is still allocated. For the same 5013reason, do not use a thread-safe function 5014after receiving a return value of <code>napi_closing</code> in response to a call to 5015<code>napi_call_threadsafe_function</code>. Data associated with the 5016<code>napi_threadsafe_function</code> can be freed in its <code>napi_finalize</code> callback which 5017was passed to <code>napi_create_threadsafe_function()</code>. The parameter 5018<code>initial_thread_count</code> of <code>napi_create_threadsafe_function</code> marks the initial 5019number of aquisitions of the thread-safe functions, instead of calling 5020<code>napi_acquire_threadsafe_function</code> multiple times at creation.</p> 5021<p>Once the number of threads making use of a <code>napi_threadsafe_function</code> reaches 5022zero, no further threads can start making use of it by calling 5023<code>napi_acquire_threadsafe_function()</code>. In fact, all subsequent API calls 5024associated with it, except <code>napi_release_threadsafe_function()</code>, will return an 5025error value of <code>napi_closing</code>.</p> 5026<p>The thread-safe function can be "aborted" by giving a value of <code>napi_tsfn_abort</code> 5027to <code>napi_release_threadsafe_function()</code>. This will cause all subsequent APIs 5028associated with the thread-safe function except 5029<code>napi_release_threadsafe_function()</code> to return <code>napi_closing</code> even before its 5030reference count reaches zero. In particular, <code>napi_call_threadsafe_function()</code> 5031will return <code>napi_closing</code>, thus informing the threads that it is no longer 5032possible to make asynchronous calls to the thread-safe function. This can be 5033used as a criterion for terminating the thread. <strong>Upon receiving a return value 5034of <code>napi_closing</code> from <code>napi_call_threadsafe_function()</code> a thread must not use 5035the thread-safe function anymore because it is no longer guaranteed to 5036be allocated.</strong></p> 5037<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> 5038<p>Similarly to libuv handles, thread-safe functions can be "referenced" and 5039"unreferenced". A "referenced" thread-safe function will cause the event loop on 5040the thread on which it is created to remain alive until the thread-safe function 5041is destroyed. In contrast, an "unreferenced" thread-safe function will not 5042prevent the event loop from exiting. The APIs <code>napi_ref_threadsafe_function</code> and 5043<code>napi_unref_threadsafe_function</code> exist for this purpose.</p> 5044<p>Neither does <code>napi_unref_threadsafe_function</code> mark the thread-safe functions as 5045able to be destroyed nor does <code>napi_ref_threadsafe_function</code> prevent it from 5046being destroyed.</p> 5047<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> 5048<div class="api_metadata"> 5049<details class="changelog"><summary>History</summary> 5050<table> 5051<tbody><tr><th>Version</th><th>Changes</th></tr> 5052<tr><td>v12.6.0, v10.17.0</td> 5053<td><p>Made <code>func</code> parameter optional with custom <code>call_js_cb</code>.</p></td></tr> 5054<tr><td>v10.6.0</td> 5055<td><p><span>Added in: v10.6.0</span></p></td></tr> 5056</tbody></table> 5057</details> 5058<span>N-API version: 4</span> 5059</div> 5060<pre><code class="language-c">NAPI_EXTERN napi_status 5061<span class="hljs-title function_">napi_create_threadsafe_function</span><span class="hljs-params">(napi_env env, 5062 napi_value func, 5063 napi_value async_resource, 5064 napi_value async_resource_name, 5065 <span class="hljs-type">size_t</span> max_queue_size, 5066 <span class="hljs-type">size_t</span> initial_thread_count, 5067 <span class="hljs-type">void</span>* thread_finalize_data, 5068 napi_finalize thread_finalize_cb, 5069 <span class="hljs-type">void</span>* context, 5070 napi_threadsafe_function_call_js call_js_cb, 5071 napi_threadsafe_function* result)</span>;</code></pre> 5072<ul> 5073<li><code>[in] env</code>: The environment that the API is invoked under.</li> 5074<li><code>[in] func</code>: An optional JavaScript function to call from another thread. It 5075must be provided if <code>NULL</code> is passed to <code>call_js_cb</code>.</li> 5076<li><code>[in] async_resource</code>: An optional object associated with the async work that 5077will 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> 5078<li><code>[in] async_resource_name</code>: A JavaScript string to provide an identifier for 5079the kind of resource that is being provided for diagnostic information exposed 5080by the <code>async_hooks</code> API.</li> 5081<li><code>[in] max_queue_size</code>: Maximum size of the queue. <code>0</code> for no limit.</li> 5082<li><code>[in] initial_thread_count</code>: The initial number of acquisitions, i.e. the 5083initial number of threads, including the main thread, which will be making use 5084of this function.</li> 5085<li><code>[in] thread_finalize_data</code>: Optional data to be passed to <code>thread_finalize_cb</code>.</li> 5086<li><code>[in] thread_finalize_cb</code>: Optional function to call when the 5087<code>napi_threadsafe_function</code> is being destroyed.</li> 5088<li><code>[in] context</code>: Optional data to attach to the resulting 5089<code>napi_threadsafe_function</code>.</li> 5090<li><code>[in] call_js_cb</code>: Optional callback which calls the JavaScript function in 5091response to a call on a different thread. This callback will be called on the 5092main thread. If not given, the JavaScript function will be called with no 5093parameters and with <code>undefined</code> as its <code>this</code> value. 5094<a href="#n_api_napi_threadsafe_function_call_js"><code>napi_threadsafe_function_call_js</code></a> provides more details.</li> 5095<li><code>[out] result</code>: The asynchronous thread-safe JavaScript function.</li> 5096</ul> 5097<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> 5098<div class="api_metadata"> 5099<span>Added in: v10.6.0</span> 5100<span>N-API version: 4</span> 5101</div> 5102<pre><code class="language-c">NAPI_EXTERN napi_status 5103<span class="hljs-title function_">napi_get_threadsafe_function_context</span><span class="hljs-params">(napi_threadsafe_function func, 5104 <span class="hljs-type">void</span>** result)</span>;</code></pre> 5105<ul> 5106<li><code>[in] func</code>: The thread-safe function for which to retrieve the context.</li> 5107<li><code>[out] result</code>: The location where to store the context.</li> 5108</ul> 5109<p>This API may be called from any thread which makes use of <code>func</code>.</p> 5110<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> 5111<div class="api_metadata"> 5112<details class="changelog"><summary>History</summary> 5113<table> 5114<tbody><tr><th>Version</th><th>Changes</th></tr> 5115<tr><td>v14.5.0</td> 5116<td><p>Support for <code>napi_would_deadlock</code> has been reverted.</p></td></tr> 5117<tr><td>v14.1.0</td> 5118<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> 5119<tr><td>v10.6.0</td> 5120<td><p><span>Added in: v10.6.0</span></p></td></tr> 5121</tbody></table> 5122</details> 5123<span>N-API version: 4</span> 5124</div> 5125<pre><code class="language-c">NAPI_EXTERN napi_status 5126<span class="hljs-title function_">napi_call_threadsafe_function</span><span class="hljs-params">(napi_threadsafe_function func, 5127 <span class="hljs-type">void</span>* data, 5128 napi_threadsafe_function_call_mode is_blocking)</span>;</code></pre> 5129<ul> 5130<li><code>[in] func</code>: The asynchronous thread-safe JavaScript function to invoke.</li> 5131<li><code>[in] data</code>: Data to send into JavaScript via the callback <code>call_js_cb</code> 5132provided during the creation of the thread-safe JavaScript function.</li> 5133<li><code>[in] is_blocking</code>: Flag whose value can be either <code>napi_tsfn_blocking</code> to 5134indicate that the call should block if the queue is full or 5135<code>napi_tsfn_nonblocking</code> to indicate that the call should return immediately 5136with a status of <code>napi_queue_full</code> whenever the queue is full.</li> 5137</ul> 5138<p>This API should not be called with <code>napi_tsfn_blocking</code> from a JavaScript 5139thread, because, if the queue is full, it may cause the JavaScript thread to 5140deadlock.</p> 5141<p>This API will return <code>napi_closing</code> if <code>napi_release_threadsafe_function()</code> was 5142called with <code>abort</code> set to <code>napi_tsfn_abort</code> from any thread. The value is only 5143added to the queue if the API returns <code>napi_ok</code>.</p> 5144<p>This API may be called from any thread which makes use of <code>func</code>.</p> 5145<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> 5146<div class="api_metadata"> 5147<span>Added in: v10.6.0</span> 5148<span>N-API version: 4</span> 5149</div> 5150<pre><code class="language-c">NAPI_EXTERN napi_status 5151<span class="hljs-title function_">napi_acquire_threadsafe_function</span><span class="hljs-params">(napi_threadsafe_function func)</span>;</code></pre> 5152<ul> 5153<li><code>[in] func</code>: The asynchronous thread-safe JavaScript function to start making 5154use of.</li> 5155</ul> 5156<p>A thread should call this API before passing <code>func</code> to any other thread-safe 5157function APIs to indicate that it will be making use of <code>func</code>. This prevents 5158<code>func</code> from being destroyed when all other threads have stopped making use of 5159it.</p> 5160<p>This API may be called from any thread which will start making use of <code>func</code>.</p> 5161<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> 5162<div class="api_metadata"> 5163<span>Added in: v10.6.0</span> 5164<span>N-API version: 4</span> 5165</div> 5166<pre><code class="language-c">NAPI_EXTERN napi_status 5167<span class="hljs-title function_">napi_release_threadsafe_function</span><span class="hljs-params">(napi_threadsafe_function func, 5168 napi_threadsafe_function_release_mode mode)</span>;</code></pre> 5169<ul> 5170<li><code>[in] func</code>: The asynchronous thread-safe JavaScript function whose reference 5171count to decrement.</li> 5172<li><code>[in] mode</code>: Flag whose value can be either <code>napi_tsfn_release</code> to indicate 5173that the current thread will make no further calls to the thread-safe 5174function, or <code>napi_tsfn_abort</code> to indicate that in addition to the current 5175thread, no other thread should make any further calls to the thread-safe 5176function. If set to <code>napi_tsfn_abort</code>, further calls to 5177<code>napi_call_threadsafe_function()</code> will return <code>napi_closing</code>, and no further 5178values will be placed in the queue.</li> 5179</ul> 5180<p>A thread should call this API when it stops making use of <code>func</code>. Passing <code>func</code> 5181to any thread-safe APIs after having called this API has undefined results, as 5182<code>func</code> may have been destroyed.</p> 5183<p>This API may be called from any thread which will stop making use of <code>func</code>.</p> 5184<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> 5185<div class="api_metadata"> 5186<span>Added in: v10.6.0</span> 5187<span>N-API version: 4</span> 5188</div> 5189<pre><code class="language-c">NAPI_EXTERN napi_status 5190<span class="hljs-title function_">napi_ref_threadsafe_function</span><span class="hljs-params">(napi_env env, napi_threadsafe_function func)</span>;</code></pre> 5191<ul> 5192<li><code>[in] env</code>: The environment that the API is invoked under.</li> 5193<li><code>[in] func</code>: The thread-safe function to reference.</li> 5194</ul> 5195<p>This API is used to indicate that the event loop running on the main thread 5196should 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 5197also idempotent.</p> 5198<p>Neither does <code>napi_unref_threadsafe_function</code> mark the thread-safe functions as 5199able to be destroyed nor does <code>napi_ref_threadsafe_function</code> prevent it from 5200being destroyed. <code>napi_acquire_threadsafe_function</code> and 5201<code>napi_release_threadsafe_function</code> are available for that purpose.</p> 5202<p>This API may only be called from the main thread.</p> 5203<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> 5204<div class="api_metadata"> 5205<span>Added in: v10.6.0</span> 5206<span>N-API version: 4</span> 5207</div> 5208<pre><code class="language-c">NAPI_EXTERN napi_status 5209<span class="hljs-title function_">napi_unref_threadsafe_function</span><span class="hljs-params">(napi_env env, napi_threadsafe_function func)</span>;</code></pre> 5210<ul> 5211<li><code>[in] env</code>: The environment that the API is invoked under.</li> 5212<li><code>[in] func</code>: The thread-safe function to unreference.</li> 5213</ul> 5214<p>This API is used to indicate that the event loop running on the main thread 5215may 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 5216idempotent.</p> 5217<p>This API may only be called from the main thread.</p> 5218</section><section><h3>Miscellaneous utilities<span><a class="mark" href="#n_api_miscellaneous_utilities" id="n_api_miscellaneous_utilities">#</a></span></h3> 5219</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> 5220<div class="api_metadata"> 5221<span>Added in: v14.18.0</span> 5222</div> 5223<p></p><div class="api_stability api_stability_1"><a href="documentation.html#documentation_stability_index">Stability: 1</a> - Experimental</div><p></p> 5224<pre><code class="language-c">NAPI_EXTERN napi_status 5225<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>; 5226</code></pre> 5227<ul> 5228<li><code>[in] env</code>: The environment that the API is invoked under.</li> 5229<li><code>[out] result</code>: A URL containing the absolute path of the 5230location from which the add-on was loaded. For a file on the local 5231file system it will start with <code>file://</code>. The string is null-terminated and 5232owned by <code>env</code> and must thus not be modified or freed.</li> 5233</ul> 5234<p><code>result</code> may be an empty string if the add-on loading process fails to establish 5235the add-on's file name during loading.</p></section> 5236 <!-- API END --> 5237 </div> 5238 </div> 5239 </div> 5240 <script> 5241 'use strict'; 5242 { 5243 const kCustomPreference = 'customDarkTheme'; 5244 const userSettings = sessionStorage.getItem(kCustomPreference); 5245 const themeToggleButton = document.getElementById('theme-toggle-btn'); 5246 if (userSettings === null && window.matchMedia) { 5247 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 5248 if ('onchange' in mq) { 5249 function mqChangeListener(e) { 5250 document.body.classList.toggle('dark-mode', e.matches); 5251 } 5252 mq.addEventListener('change', mqChangeListener); 5253 if (themeToggleButton) { 5254 themeToggleButton.addEventListener('click', function() { 5255 mq.removeEventListener('change', mqChangeListener); 5256 }, { once: true }); 5257 } 5258 } 5259 if (mq.matches) { 5260 document.body.classList.add('dark-mode'); 5261 } 5262 } else if (userSettings === 'true') { 5263 document.body.classList.add('dark-mode'); 5264 } 5265 if (themeToggleButton) { 5266 themeToggleButton.hidden = false; 5267 themeToggleButton.addEventListener('click', function() { 5268 sessionStorage.setItem( 5269 kCustomPreference, 5270 document.body.classList.toggle('dark-mode') 5271 ); 5272 }); 5273 } 5274 } 5275 </script> 5276</body> 5277</html> 5278