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<header> 91 <div class="header-container"> 92 <h1>Node.js v14.20.1 documentation</h1> 93 <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 94 <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 95 <path fill="none" d="M0 0h24v24H0z" /> 96 <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 97 <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 98 </svg> 99 <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 100 <path d="M0 0h24v24H0z" fill="none" /> 101 <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 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href="https://nodejs.org/docs/latest-v0.10.x/api/util.html">0.10.x</a></li></ol> 136 </li> 137 138 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/util.md">Edit on GitHub</a></li> 139 </ul> 140 </div> 141 <hr> 142 </header> 143 144 <details id="toc" open><summary>Table of contents</summary><ul> 145<li><span class="stability_2"><a href="#util_util">Util</a></span> 146<ul> 147<li><a href="#util_util_callbackify_original"><code>util.callbackify(original)</code></a></li> 148<li><a href="#util_util_debuglog_section_callback"><code>util.debuglog(section[, callback])</code></a> 149<ul> 150<li><a href="#util_debuglog_enabled"><code>debuglog().enabled</code></a></li> 151</ul> 152</li> 153<li><a href="#util_util_debug_section"><code>util.debug(section)</code></a></li> 154<li><a href="#util_util_deprecate_fn_msg_code"><code>util.deprecate(fn, msg[, code])</code></a></li> 155<li><a href="#util_util_format_format_args"><code>util.format(format[, ...args])</code></a></li> 156<li><a href="#util_util_formatwithoptions_inspectoptions_format_args"><code>util.formatWithOptions(inspectOptions, format[, ...args])</code></a></li> 157<li><a href="#util_util_getsystemerrorname_err"><code>util.getSystemErrorName(err)</code></a></li> 158<li><a href="#util_util_getsystemerrormap"><code>util.getSystemErrorMap()</code></a></li> 159<li><span class="stability_3"><a href="#util_util_inherits_constructor_superconstructor"><code>util.inherits(constructor, superConstructor)</code></a></span></li> 160<li><a href="#util_util_inspect_object_options"><code>util.inspect(object[, options])</code></a></li> 161<li><a href="#util_util_inspect_object_showhidden_depth_colors"><code>util.inspect(object[, showHidden[, depth[, colors]]])</code></a> 162<ul> 163<li><a href="#util_customizing_util_inspect_colors">Customizing <code>util.inspect</code> colors</a> 164<ul> 165<li><a href="#util_modifiers">Modifiers</a></li> 166<li><a href="#util_foreground_colors">Foreground colors</a></li> 167<li><a href="#util_background_colors">Background colors</a></li> 168</ul> 169</li> 170<li><a href="#util_custom_inspection_functions_on_objects">Custom inspection functions on objects</a></li> 171<li><a href="#util_util_inspect_custom"><code>util.inspect.custom</code></a></li> 172<li><a href="#util_util_inspect_defaultoptions"><code>util.inspect.defaultOptions</code></a></li> 173</ul> 174</li> 175<li><a href="#util_util_isdeepstrictequal_val1_val2"><code>util.isDeepStrictEqual(val1, val2)</code></a></li> 176<li><a href="#util_util_promisify_original"><code>util.promisify(original)</code></a> 177<ul> 178<li><a href="#util_custom_promisified_functions">Custom promisified functions</a></li> 179<li><a href="#util_util_promisify_custom"><code>util.promisify.custom</code></a></li> 180</ul> 181</li> 182<li><a href="#util_class_util_textdecoder">Class: <code>util.TextDecoder</code></a> 183<ul> 184<li><a href="#util_whatwg_supported_encodings">WHATWG supported encodings</a> 185<ul> 186<li><a href="#util_encodings_supported_by_default_with_full_icu_data">Encodings supported by default (with full ICU data)</a></li> 187<li><a href="#util_encodings_supported_when_node_js_is_built_with_the_small_icu_option">Encodings supported when Node.js is built with the <code>small-icu</code> option</a></li> 188<li><a href="#util_encodings_supported_when_icu_is_disabled">Encodings supported when ICU is disabled</a></li> 189</ul> 190</li> 191<li><a href="#util_new_textdecoder_encoding_options"><code>new TextDecoder([encoding[, options]])</code></a></li> 192<li><a href="#util_textdecoder_decode_input_options"><code>textDecoder.decode([input[, options]])</code></a></li> 193<li><a href="#util_textdecoder_encoding"><code>textDecoder.encoding</code></a></li> 194<li><a href="#util_textdecoder_fatal"><code>textDecoder.fatal</code></a></li> 195<li><a href="#util_textdecoder_ignorebom"><code>textDecoder.ignoreBOM</code></a></li> 196</ul> 197</li> 198<li><a href="#util_class_util_textencoder">Class: <code>util.TextEncoder</code></a> 199<ul> 200<li><a href="#util_textencoder_encode_input"><code>textEncoder.encode([input])</code></a></li> 201<li><a href="#util_textencoder_encodeinto_src_dest"><code>textEncoder.encodeInto(src, dest)</code></a></li> 202<li><a href="#util_textencoder_encoding"><code>textEncoder.encoding</code></a></li> 203</ul> 204</li> 205<li><a href="#util_util_tousvstring_string"><code>util.toUSVString(string)</code></a></li> 206<li><a href="#util_util_types"><code>util.types</code></a> 207<ul> 208<li><a href="#util_util_types_isanyarraybuffer_value"><code>util.types.isAnyArrayBuffer(value)</code></a></li> 209<li><a href="#util_util_types_isarraybufferview_value"><code>util.types.isArrayBufferView(value)</code></a></li> 210<li><a href="#util_util_types_isargumentsobject_value"><code>util.types.isArgumentsObject(value)</code></a></li> 211<li><a href="#util_util_types_isarraybuffer_value"><code>util.types.isArrayBuffer(value)</code></a></li> 212<li><a href="#util_util_types_isasyncfunction_value"><code>util.types.isAsyncFunction(value)</code></a></li> 213<li><a href="#util_util_types_isbigint64array_value"><code>util.types.isBigInt64Array(value)</code></a></li> 214<li><a href="#util_util_types_isbiguint64array_value"><code>util.types.isBigUint64Array(value)</code></a></li> 215<li><a href="#util_util_types_isbooleanobject_value"><code>util.types.isBooleanObject(value)</code></a></li> 216<li><a href="#util_util_types_isboxedprimitive_value"><code>util.types.isBoxedPrimitive(value)</code></a></li> 217<li><a href="#util_util_types_isdataview_value"><code>util.types.isDataView(value)</code></a></li> 218<li><a href="#util_util_types_isdate_value"><code>util.types.isDate(value)</code></a></li> 219<li><a href="#util_util_types_isexternal_value"><code>util.types.isExternal(value)</code></a></li> 220<li><a href="#util_util_types_isfloat32array_value"><code>util.types.isFloat32Array(value)</code></a></li> 221<li><a href="#util_util_types_isfloat64array_value"><code>util.types.isFloat64Array(value)</code></a></li> 222<li><a href="#util_util_types_isgeneratorfunction_value"><code>util.types.isGeneratorFunction(value)</code></a></li> 223<li><a href="#util_util_types_isgeneratorobject_value"><code>util.types.isGeneratorObject(value)</code></a></li> 224<li><a href="#util_util_types_isint8array_value"><code>util.types.isInt8Array(value)</code></a></li> 225<li><a href="#util_util_types_isint16array_value"><code>util.types.isInt16Array(value)</code></a></li> 226<li><a href="#util_util_types_isint32array_value"><code>util.types.isInt32Array(value)</code></a></li> 227<li><a href="#util_util_types_ismap_value"><code>util.types.isMap(value)</code></a></li> 228<li><a href="#util_util_types_ismapiterator_value"><code>util.types.isMapIterator(value)</code></a></li> 229<li><a href="#util_util_types_ismodulenamespaceobject_value"><code>util.types.isModuleNamespaceObject(value)</code></a></li> 230<li><a href="#util_util_types_isnativeerror_value"><code>util.types.isNativeError(value)</code></a></li> 231<li><a href="#util_util_types_isnumberobject_value"><code>util.types.isNumberObject(value)</code></a></li> 232<li><a href="#util_util_types_ispromise_value"><code>util.types.isPromise(value)</code></a></li> 233<li><a href="#util_util_types_isproxy_value"><code>util.types.isProxy(value)</code></a></li> 234<li><a href="#util_util_types_isregexp_value"><code>util.types.isRegExp(value)</code></a></li> 235<li><a href="#util_util_types_isset_value"><code>util.types.isSet(value)</code></a></li> 236<li><a href="#util_util_types_issetiterator_value"><code>util.types.isSetIterator(value)</code></a></li> 237<li><a href="#util_util_types_issharedarraybuffer_value"><code>util.types.isSharedArrayBuffer(value)</code></a></li> 238<li><a href="#util_util_types_isstringobject_value"><code>util.types.isStringObject(value)</code></a></li> 239<li><a href="#util_util_types_issymbolobject_value"><code>util.types.isSymbolObject(value)</code></a></li> 240<li><a href="#util_util_types_istypedarray_value"><code>util.types.isTypedArray(value)</code></a></li> 241<li><a href="#util_util_types_isuint8array_value"><code>util.types.isUint8Array(value)</code></a></li> 242<li><a href="#util_util_types_isuint8clampedarray_value"><code>util.types.isUint8ClampedArray(value)</code></a></li> 243<li><a href="#util_util_types_isuint16array_value"><code>util.types.isUint16Array(value)</code></a></li> 244<li><a href="#util_util_types_isuint32array_value"><code>util.types.isUint32Array(value)</code></a></li> 245<li><a href="#util_util_types_isweakmap_value"><code>util.types.isWeakMap(value)</code></a></li> 246<li><a href="#util_util_types_isweakset_value"><code>util.types.isWeakSet(value)</code></a></li> 247<li><span class="stability_0"><a href="#util_util_types_iswebassemblycompiledmodule_value"><code>util.types.isWebAssemblyCompiledModule(value)</code></a></span></li> 248</ul> 249</li> 250<li><a href="#util_deprecated_apis">Deprecated APIs</a> 251<ul> 252<li><span class="stability_0"><a href="#util_util_extend_target_source"><code>util._extend(target, source)</code></a></span></li> 253<li><span class="stability_0"><a href="#util_util_isarray_object"><code>util.isArray(object)</code></a></span></li> 254<li><span class="stability_0"><a href="#util_util_isboolean_object"><code>util.isBoolean(object)</code></a></span></li> 255<li><span class="stability_0"><a href="#util_util_isbuffer_object"><code>util.isBuffer(object)</code></a></span></li> 256<li><span class="stability_0"><a href="#util_util_isdate_object"><code>util.isDate(object)</code></a></span></li> 257<li><span class="stability_0"><a href="#util_util_iserror_object"><code>util.isError(object)</code></a></span></li> 258<li><span class="stability_0"><a href="#util_util_isfunction_object"><code>util.isFunction(object)</code></a></span></li> 259<li><span class="stability_0"><a href="#util_util_isnull_object"><code>util.isNull(object)</code></a></span></li> 260<li><span class="stability_0"><a href="#util_util_isnullorundefined_object"><code>util.isNullOrUndefined(object)</code></a></span></li> 261<li><span class="stability_0"><a href="#util_util_isnumber_object"><code>util.isNumber(object)</code></a></span></li> 262<li><span class="stability_0"><a href="#util_util_isobject_object"><code>util.isObject(object)</code></a></span></li> 263<li><span class="stability_0"><a href="#util_util_isprimitive_object"><code>util.isPrimitive(object)</code></a></span></li> 264<li><span class="stability_0"><a href="#util_util_isregexp_object"><code>util.isRegExp(object)</code></a></span></li> 265<li><span class="stability_0"><a href="#util_util_isstring_object"><code>util.isString(object)</code></a></span></li> 266<li><span class="stability_0"><a href="#util_util_issymbol_object"><code>util.isSymbol(object)</code></a></span></li> 267<li><span class="stability_0"><a href="#util_util_isundefined_object"><code>util.isUndefined(object)</code></a></span></li> 268<li><span class="stability_0"><a href="#util_util_log_string"><code>util.log(string)</code></a></span></li> 269</ul> 270</li> 271</ul> 272</li> 273</ul></details> 274 275 <div id="apicontent"> 276 <h2>Util<span><a class="mark" href="#util_util" id="util_util">#</a></span></h2> 277 278<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 279<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v14.20.1/lib/util.js">lib/util.js</a></p> 280<p>The <code>util</code> module supports the needs of Node.js internal APIs. Many of the 281utilities are useful for application and module developers as well. To access 282it:</p> 283<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>);</code></pre> 284<section><h3><code>util.callbackify(original)</code><span><a class="mark" href="#util_util_callbackify_original" id="util_util_callbackify_original">#</a></span></h3> 285<div class="api_metadata"> 286<span>Added in: v8.2.0</span> 287</div> 288<ul> 289<li><code>original</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> An <code>async</code> function</li> 290<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> a callback style function</li> 291</ul> 292<p>Takes an <code>async</code> function (or a function that returns a <code>Promise</code>) and returns a 293function following the error-first callback style, i.e. taking 294an <code>(err, value) => ...</code> callback as the last argument. In the callback, the 295first argument will be the rejection reason (or <code>null</code> if the <code>Promise</code> 296resolved), and the second argument will be the resolved value.</p> 297<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 298 299<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">fn</span>(<span class="hljs-params"></span>) { 300 <span class="hljs-keyword">return</span> <span class="hljs-string">'hello world'</span>; 301} 302<span class="hljs-keyword">const</span> callbackFunction = util.<span class="hljs-title function_">callbackify</span>(fn); 303 304<span class="hljs-title function_">callbackFunction</span>(<span class="hljs-function">(<span class="hljs-params">err, ret</span>) =></span> { 305 <span class="hljs-keyword">if</span> (err) <span class="hljs-keyword">throw</span> err; 306 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(ret); 307});</code></pre> 308<p>Will print:</p> 309<pre><code class="language-text">hello world</code></pre> 310<p>The callback is executed asynchronously, and will have a limited stack trace. 311If the callback throws, the process will emit an <a href="process.html#process_event_uncaughtexception"><code>'uncaughtException'</code></a> 312event, and if not handled will exit.</p> 313<p>Since <code>null</code> has a special meaning as the first argument to a callback, if a 314wrapped function rejects a <code>Promise</code> with a falsy value as a reason, the value 315is wrapped in an <code>Error</code> with the original value stored in a field named 316<code>reason</code>.</p> 317<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">fn</span>(<span class="hljs-params"></span>) { 318 <span class="hljs-keyword">return</span> <span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">reject</span>(<span class="hljs-literal">null</span>); 319} 320<span class="hljs-keyword">const</span> callbackFunction = util.<span class="hljs-title function_">callbackify</span>(fn); 321 322<span class="hljs-title function_">callbackFunction</span>(<span class="hljs-function">(<span class="hljs-params">err, ret</span>) =></span> { 323 <span class="hljs-comment">// When the Promise was rejected with `null` it is wrapped with an Error and</span> 324 <span class="hljs-comment">// the original value is stored in `reason`.</span> 325 err && err.<span class="hljs-title function_">hasOwnProperty</span>(<span class="hljs-string">'reason'</span>) && err.<span class="hljs-property">reason</span> === <span class="hljs-literal">null</span>; <span class="hljs-comment">// true</span> 326});</code></pre> 327</section><section><h3><code>util.debuglog(section[, callback])</code><span><a class="mark" href="#util_util_debuglog_section_callback" id="util_util_debuglog_section_callback">#</a></span></h3> 328<div class="api_metadata"> 329<span>Added in: v0.11.3</span> 330</div> 331<ul> 332<li><code>section</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string identifying the portion of the application for 333which the <code>debuglog</code> function is being created.</li> 334<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A callback invoked the first time the logging function 335is called with a function argument that is a more optimized logging function.</li> 336<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The logging function</li> 337</ul> 338<p>The <code>util.debuglog()</code> method is used to create a function that conditionally 339writes debug messages to <code>stderr</code> based on the existence of the <code>NODE_DEBUG</code> 340environment variable. If the <code>section</code> name appears within the value of that 341environment variable, then the returned function operates similar to 342<a href="console.html#console_console_error_data_args"><code>console.error()</code></a>. If not, then the returned function is a no-op.</p> 343<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 344<span class="hljs-keyword">const</span> debuglog = util.<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'foo'</span>); 345 346<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'hello from foo [%d]'</span>, <span class="hljs-number">123</span>);</code></pre> 347<p>If this program is run with <code>NODE_DEBUG=foo</code> in the environment, then 348it will output something like:</p> 349<pre><code class="language-console">FOO 3245: hello from foo [123]</code></pre> 350<p>where <code>3245</code> is the process id. If it is not run with that 351environment variable set, then it will not print anything.</p> 352<p>The <code>section</code> supports wildcard also:</p> 353<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 354<span class="hljs-keyword">const</span> debuglog = util.<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'foo-bar'</span>); 355 356<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'hi there, it\'s foo-bar [%d]'</span>, <span class="hljs-number">2333</span>);</code></pre> 357<p>if it is run with <code>NODE_DEBUG=foo*</code> in the environment, then it will output 358something like:</p> 359<pre><code class="language-console">FOO-BAR 3257: hi there, it's foo-bar [2333]</code></pre> 360<p>Multiple comma-separated <code>section</code> names may be specified in the <code>NODE_DEBUG</code> 361environment variable: <code>NODE_DEBUG=fs,net,tls</code>.</p> 362<p>The optional <code>callback</code> argument can be used to replace the logging function 363with a different function that doesn't have any initialization or 364unnecessary wrapping.</p> 365<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 366<span class="hljs-keyword">let</span> debuglog = util.<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'internals'</span>, <span class="hljs-function">(<span class="hljs-params">debug</span>) =></span> { 367 <span class="hljs-comment">// Replace with a logging function that optimizes out</span> 368 <span class="hljs-comment">// testing if the section is enabled</span> 369 debuglog = debug; 370});</code></pre> 371<h4><code>debuglog().enabled</code><span><a class="mark" href="#util_debuglog_enabled" id="util_debuglog_enabled">#</a></span></h4> 372<div class="api_metadata"> 373<span>Added in: v14.9.0</span> 374</div> 375<ul> 376<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 377</ul> 378<p>The <code>util.debuglog().enabled</code> getter is used to create a test that can be used 379in conditionals based on the existence of the <code>NODE_DEBUG</code> environment variable. 380If the <code>section</code> name appears within the value of that environment variable, 381then the returned value will be <code>true</code>. If not, then the returned value will be 382<code>false</code>.</p> 383<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 384<span class="hljs-keyword">const</span> enabled = util.<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'foo'</span>).<span class="hljs-property">enabled</span>; 385<span class="hljs-keyword">if</span> (enabled) { 386 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'hello from foo [%d]'</span>, <span class="hljs-number">123</span>); 387}</code></pre> 388<p>If this program is run with <code>NODE_DEBUG=foo</code> in the environment, then it will 389output something like:</p> 390<pre><code class="language-console">hello from foo [123]</code></pre> 391</section><section><h3><code>util.debug(section)</code><span><a class="mark" href="#util_util_debug_section" id="util_util_debug_section">#</a></span></h3> 392<div class="api_metadata"> 393<span>Added in: v14.9.0</span> 394</div> 395<p>Alias for <code>util.debuglog</code>. Usage allows for readability of that doesn't imply 396logging when only using <code>util.debuglog().enabled</code>.</p> 397</section><section><h3><code>util.deprecate(fn, msg[, code])</code><span><a class="mark" href="#util_util_deprecate_fn_msg_code" id="util_util_deprecate_fn_msg_code">#</a></span></h3> 398<div class="api_metadata"> 399<details class="changelog"><summary>History</summary> 400<table> 401<tbody><tr><th>Version</th><th>Changes</th></tr> 402<tr><td>v10.0.0</td> 403<td><p>Deprecation warnings are only emitted once for each code.</p></td></tr> 404<tr><td>v0.8.0</td> 405<td><p><span>Added in: v0.8.0</span></p></td></tr> 406</tbody></table> 407</details> 408</div> 409<ul> 410<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The function that is being deprecated.</li> 411<li><code>msg</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A warning message to display when the deprecated function is 412invoked.</li> 413<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A deprecation code. See the <a href="deprecations.html#deprecations_list_of_deprecated_apis">list of deprecated APIs</a> for a 414list of codes.</li> 415<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> The deprecated function wrapped to emit a warning.</li> 416</ul> 417<p>The <code>util.deprecate()</code> method wraps <code>fn</code> (which may be a function or class) in 418such a way that it is marked as deprecated.</p> 419<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 420 421<span class="hljs-built_in">exports</span>.<span class="hljs-property">obsoleteFunction</span> = util.<span class="hljs-title function_">deprecate</span>(<span class="hljs-function">() =></span> { 422 <span class="hljs-comment">// Do something here.</span> 423}, <span class="hljs-string">'obsoleteFunction() is deprecated. Use newShinyFunction() instead.'</span>);</code></pre> 424<p>When called, <code>util.deprecate()</code> will return a function that will emit a 425<code>DeprecationWarning</code> using the <a href="process.html#process_event_warning"><code>'warning'</code></a> event. The warning will 426be emitted and printed to <code>stderr</code> the first time the returned function is 427called. After the warning is emitted, the wrapped function is called without 428emitting a warning.</p> 429<p>If the same optional <code>code</code> is supplied in multiple calls to <code>util.deprecate()</code>, 430the warning will be emitted only once for that <code>code</code>.</p> 431<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 432 433<span class="hljs-keyword">const</span> fn1 = util.<span class="hljs-title function_">deprecate</span>(someFunction, someMessage, <span class="hljs-string">'DEP0001'</span>); 434<span class="hljs-keyword">const</span> fn2 = util.<span class="hljs-title function_">deprecate</span>(someOtherFunction, someOtherMessage, <span class="hljs-string">'DEP0001'</span>); 435<span class="hljs-title function_">fn1</span>(); <span class="hljs-comment">// Emits a deprecation warning with code DEP0001</span> 436<span class="hljs-title function_">fn2</span>(); <span class="hljs-comment">// Does not emit a deprecation warning because it has the same code</span></code></pre> 437<p>If either the <code>--no-deprecation</code> or <code>--no-warnings</code> command-line flags are 438used, or if the <code>process.noDeprecation</code> property is set to <code>true</code> <em>prior</em> to 439the first deprecation warning, the <code>util.deprecate()</code> method does nothing.</p> 440<p>If the <code>--trace-deprecation</code> or <code>--trace-warnings</code> command-line flags are set, 441or the <code>process.traceDeprecation</code> property is set to <code>true</code>, a warning and a 442stack trace are printed to <code>stderr</code> the first time the deprecated function is 443called.</p> 444<p>If the <code>--throw-deprecation</code> command-line flag is set, or the 445<code>process.throwDeprecation</code> property is set to <code>true</code>, then an exception will be 446thrown when the deprecated function is called.</p> 447<p>The <code>--throw-deprecation</code> command-line flag and <code>process.throwDeprecation</code> 448property take precedence over <code>--trace-deprecation</code> and 449<code>process.traceDeprecation</code>.</p> 450</section><section><h3><code>util.format(format[, ...args])</code><span><a class="mark" href="#util_util_format_format_args" id="util_util_format_format_args">#</a></span></h3> 451<div class="api_metadata"> 452<details class="changelog"><summary>History</summary> 453<table> 454<tbody><tr><th>Version</th><th>Changes</th></tr> 455<tr><td>v12.11.0</td> 456<td><p>The <code>%c</code> specifier is ignored now.</p></td></tr> 457<tr><td>v12.0.0</td> 458<td><p>The <code>format</code> argument is now only taken as such if it actually contains format specifiers.</p></td></tr> 459<tr><td>v12.0.0</td> 460<td><p>If the <code>format</code> argument is not a format string, the output string's formatting is no longer dependent on the type of the first argument. This change removes previously present quotes from strings that were being output when the first argument was not a string.</p></td></tr> 461<tr><td>v11.4.0</td> 462<td><p>The <code>%d</code>, <code>%f</code> and <code>%i</code> specifiers now support Symbols properly.</p></td></tr> 463<tr><td>v11.4.0</td> 464<td><p>The <code>%o</code> specifier's <code>depth</code> has default depth of 4 again.</p></td></tr> 465<tr><td>v11.0.0</td> 466<td><p>The <code>%o</code> specifier's <code>depth</code> option will now fall back to the default depth.</p></td></tr> 467<tr><td>v10.12.0</td> 468<td><p>The <code>%d</code> and <code>%i</code> specifiers now support BigInt.</p></td></tr> 469<tr><td>v8.4.0</td> 470<td><p>The <code>%o</code> and <code>%O</code> specifiers are supported now.</p></td></tr> 471<tr><td>v0.5.3</td> 472<td><p><span>Added in: v0.5.3</span></p></td></tr> 473</tbody></table> 474</details> 475</div> 476<ul> 477<li><code>format</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A <code>printf</code>-like format string.</li> 478</ul> 479<p>The <code>util.format()</code> method returns a formatted string using the first argument 480as a <code>printf</code>-like format string which can contain zero or more format 481specifiers. Each specifier is replaced with the converted value from the 482corresponding argument. Supported specifiers are:</p> 483<ul> 484<li><code>%s</code>: <code>String</code> will be used to convert all values except <code>BigInt</code>, <code>Object</code> 485and <code>-0</code>. <code>BigInt</code> values will be represented with an <code>n</code> and Objects that 486have no user defined <code>toString</code> function are inspected using <code>util.inspect()</code> 487with options <code>{ depth: 0, colors: false, compact: 3 }</code>.</li> 488<li><code>%d</code>: <code>Number</code> will be used to convert all values except <code>BigInt</code> and 489<code>Symbol</code>.</li> 490<li><code>%i</code>: <code>parseInt(value, 10)</code> is used for all values except <code>BigInt</code> and 491<code>Symbol</code>.</li> 492<li><code>%f</code>: <code>parseFloat(value)</code> is used for all values expect <code>Symbol</code>.</li> 493<li><code>%j</code>: JSON. Replaced with the string <code>'[Circular]'</code> if the argument contains 494circular references.</li> 495<li><code>%o</code>: <code>Object</code>. A string representation of an object with generic JavaScript 496object formatting. Similar to <code>util.inspect()</code> with options 497<code>{ showHidden: true, showProxy: true }</code>. This will show the full object 498including non-enumerable properties and proxies.</li> 499<li><code>%O</code>: <code>Object</code>. A string representation of an object with generic JavaScript 500object formatting. Similar to <code>util.inspect()</code> without options. This will show 501the full object not including non-enumerable properties and proxies.</li> 502<li><code>%c</code>: <code>CSS</code>. This specifier is ignored and will skip any CSS passed in.</li> 503<li><code>%%</code>: single percent sign (<code>'%'</code>). This does not consume an argument.</li> 504<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The formatted string</li> 505</ul> 506<p>If a specifier does not have a corresponding argument, it is not replaced:</p> 507<pre><code class="language-js">util.<span class="hljs-title function_">format</span>(<span class="hljs-string">'%s:%s'</span>, <span class="hljs-string">'foo'</span>); 508<span class="hljs-comment">// Returns: 'foo:%s'</span></code></pre> 509<p>Values that are not part of the format string are formatted using 510<code>util.inspect()</code> if their type is not <code>string</code>.</p> 511<p>If there are more arguments passed to the <code>util.format()</code> method than the 512number of specifiers, the extra arguments are concatenated to the returned 513string, separated by spaces:</p> 514<pre><code class="language-js">util.<span class="hljs-title function_">format</span>(<span class="hljs-string">'%s:%s'</span>, <span class="hljs-string">'foo'</span>, <span class="hljs-string">'bar'</span>, <span class="hljs-string">'baz'</span>); 515<span class="hljs-comment">// Returns: 'foo:bar baz'</span></code></pre> 516<p>If the first argument does not contain a valid format specifier, <code>util.format()</code> 517returns a string that is the concatenation of all arguments separated by spaces:</p> 518<pre><code class="language-js">util.<span class="hljs-title function_">format</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>); 519<span class="hljs-comment">// Returns: '1 2 3'</span></code></pre> 520<p>If only one argument is passed to <code>util.format()</code>, it is returned as it is 521without any formatting:</p> 522<pre><code class="language-js">util.<span class="hljs-title function_">format</span>(<span class="hljs-string">'%% %s'</span>); 523<span class="hljs-comment">// Returns: '%% %s'</span></code></pre> 524<p><code>util.format()</code> is a synchronous method that is intended as a debugging tool. 525Some input values can have a significant performance overhead that can block the 526event loop. Use this function with care and never in a hot code path.</p> 527</section><section><h3><code>util.formatWithOptions(inspectOptions, format[, ...args])</code><span><a class="mark" href="#util_util_formatwithoptions_inspectoptions_format_args" id="util_util_formatwithoptions_inspectoptions_format_args">#</a></span></h3> 528<div class="api_metadata"> 529<span>Added in: v10.0.0</span> 530</div> 531<ul> 532<li><code>inspectOptions</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 533<li><code>format</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 534</ul> 535<p>This function is identical to <a href="#util_util_format_format_args"><code>util.format()</code></a>, except in that it takes 536an <code>inspectOptions</code> argument which specifies options that are passed along to 537<a href="#util_util_inspect_object_options"><code>util.inspect()</code></a>.</p> 538<pre><code class="language-js">util.<span class="hljs-title function_">formatWithOptions</span>({ <span class="hljs-attr">colors</span>: <span class="hljs-literal">true</span> }, <span class="hljs-string">'See object %O'</span>, { <span class="hljs-attr">foo</span>: <span class="hljs-number">42</span> }); 539<span class="hljs-comment">// Returns 'See object { foo: 42 }', where `42` is colored as a number</span> 540<span class="hljs-comment">// when printed to a terminal.</span></code></pre> 541</section><section><h3><code>util.getSystemErrorName(err)</code><span><a class="mark" href="#util_util_getsystemerrorname_err" id="util_util_getsystemerrorname_err">#</a></span></h3> 542<div class="api_metadata"> 543<span>Added in: v9.7.0</span> 544</div> 545<ul> 546<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 547<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 548</ul> 549<p>Returns the string name for a numeric error code that comes from a Node.js API. 550The mapping between error codes and error names is platform-dependent. 551See <a href="errors.html#errors_common_system_errors">Common System Errors</a> for the names of common errors.</p> 552<pre><code class="language-js">fs.<span class="hljs-title function_">access</span>(<span class="hljs-string">'file/that/does/not/exist'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 553 <span class="hljs-keyword">const</span> name = util.<span class="hljs-title function_">getSystemErrorName</span>(err.<span class="hljs-property">errno</span>); 554 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(name); <span class="hljs-comment">// ENOENT</span> 555});</code></pre> 556</section><section><h3><code>util.getSystemErrorMap()</code><span><a class="mark" href="#util_util_getsystemerrormap" id="util_util_getsystemerrormap">#</a></span></h3> 557<div class="api_metadata"> 558<span>Added in: v14.17.0</span> 559</div> 560<ul> 561<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map" class="type"><Map></a></li> 562</ul> 563<p>Returns a Map of all system error codes available from the Node.js API. 564The mapping between error codes and error names is platform-dependent. 565See <a href="errors.html#errors_common_system_errors">Common System Errors</a> for the names of common errors.</p> 566<pre><code class="language-js">fs.<span class="hljs-title function_">access</span>(<span class="hljs-string">'file/that/does/not/exist'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 567 <span class="hljs-keyword">const</span> errorMap = util.<span class="hljs-title function_">getSystemErrorMap</span>(); 568 <span class="hljs-keyword">const</span> name = errorMap.<span class="hljs-title function_">get</span>(err.<span class="hljs-property">errno</span>); 569 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(name); <span class="hljs-comment">// ENOENT</span> 570});</code></pre> 571</section><section><h3><code>util.inherits(constructor, superConstructor)</code><span><a class="mark" href="#util_util_inherits_constructor_superconstructor" id="util_util_inherits_constructor_superconstructor">#</a></span></h3> 572<div class="api_metadata"> 573<details class="changelog"><summary>History</summary> 574<table> 575<tbody><tr><th>Version</th><th>Changes</th></tr> 576<tr><td>v5.0.0</td> 577<td><p>The <code>constructor</code> parameter can refer to an ES6 class now.</p></td></tr> 578<tr><td>v0.3.0</td> 579<td><p><span>Added in: v0.3.0</span></p></td></tr> 580</tbody></table> 581</details> 582</div> 583<p></p><div class="api_stability api_stability_3"><a href="documentation.html#documentation_stability_index">Stability: 3</a> - Legacy: Use ES2015 class syntax and <code>extends</code> keyword instead.</div><p></p> 584<ul> 585<li><code>constructor</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 586<li><code>superConstructor</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 587</ul> 588<p>Usage of <code>util.inherits()</code> is discouraged. Please use the ES6 <code>class</code> and 589<code>extends</code> keywords to get language level inheritance support. Also note 590that the two styles are <a href="https://github.com/nodejs/node/issues/4179">semantically incompatible</a>.</p> 591<p>Inherit the prototype methods from one <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor">constructor</a> into another. The 592prototype of <code>constructor</code> will be set to a new object created from 593<code>superConstructor</code>.</p> 594<p>This mainly adds some input validation on top of 595<code>Object.setPrototypeOf(constructor.prototype, superConstructor.prototype)</code>. 596As an additional convenience, <code>superConstructor</code> will be accessible 597through the <code>constructor.super_</code> property.</p> 598<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 599<span class="hljs-keyword">const</span> <span class="hljs-title class_">EventEmitter</span> = <span class="hljs-built_in">require</span>(<span class="hljs-string">'events'</span>); 600 601<span class="hljs-keyword">function</span> <span class="hljs-title function_">MyStream</span>(<span class="hljs-params"></span>) { 602 <span class="hljs-title class_">EventEmitter</span>.<span class="hljs-title function_">call</span>(<span class="hljs-variable language_">this</span>); 603} 604 605util.<span class="hljs-title function_">inherits</span>(<span class="hljs-title class_">MyStream</span>, <span class="hljs-title class_">EventEmitter</span>); 606 607<span class="hljs-title class_">MyStream</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>.<span class="hljs-property">write</span> = <span class="hljs-keyword">function</span>(<span class="hljs-params">data</span>) { 608 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">emit</span>(<span class="hljs-string">'data'</span>, data); 609}; 610 611<span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyStream</span>(); 612 613<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(stream <span class="hljs-keyword">instanceof</span> <span class="hljs-title class_">EventEmitter</span>); <span class="hljs-comment">// true</span> 614<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title class_">MyStream</span>.<span class="hljs-property">super_</span> === <span class="hljs-title class_">EventEmitter</span>); <span class="hljs-comment">// true</span> 615 616stream.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 617 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received data: "<span class="hljs-subst">${data}</span>"`</span>); 618}); 619stream.<span class="hljs-title function_">write</span>(<span class="hljs-string">'It works!'</span>); <span class="hljs-comment">// Received data: "It works!"</span></code></pre> 620<p>ES6 example using <code>class</code> and <code>extends</code>:</p> 621<pre><code class="language-js"><span class="hljs-keyword">const</span> <span class="hljs-title class_">EventEmitter</span> = <span class="hljs-built_in">require</span>(<span class="hljs-string">'events'</span>); 622 623<span class="hljs-keyword">class</span> <span class="hljs-title class_">MyStream</span> <span class="hljs-keyword">extends</span> <span class="hljs-title class_ inherited__">EventEmitter</span> { 624 <span class="hljs-title function_">write</span>(<span class="hljs-params">data</span>) { 625 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">emit</span>(<span class="hljs-string">'data'</span>, data); 626 } 627} 628 629<span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyStream</span>(); 630 631stream.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 632 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received data: "<span class="hljs-subst">${data}</span>"`</span>); 633}); 634stream.<span class="hljs-title function_">write</span>(<span class="hljs-string">'With ES6'</span>);</code></pre> 635</section><section><h3><code>util.inspect(object[, options])</code><span><a class="mark" href="#util_util_inspect_object_options" id="util_util_inspect_object_options">#</a></span></h3> 636</section><section><h3><code>util.inspect(object[, showHidden[, depth[, colors]]])</code><span><a class="mark" href="#util_util_inspect_object_showhidden_depth_colors" id="util_util_inspect_object_showhidden_depth_colors">#</a></span></h3> 637<div class="api_metadata"> 638<details class="changelog"><summary>History</summary> 639<table> 640<tbody><tr><th>Version</th><th>Changes</th></tr> 641<tr><td>v13.0.0</td> 642<td><p>Circular references now include a marker to the reference.</p></td></tr> 643<tr><td>v14.6.0, v12.19.0</td> 644<td><p>If <code>object</code> is from a different <code>vm.Context</code> now, a custom inspection function on it will not receive context-specific arguments anymore.</p></td></tr> 645<tr><td>v13.13.0, v12.17.0</td> 646<td><p>The <code>maxStringLength</code> option is supported now.</p></td></tr> 647<tr><td>v13.5.0, v12.16.0</td> 648<td><p>User defined prototype properties are inspected in case <code>showHidden</code> is <code>true</code>.</p></td></tr> 649<tr><td>v12.0.0</td> 650<td><p>The <code>compact</code> options default is changed to <code>3</code> and the <code>breakLength</code> options default is changed to <code>80</code>.</p></td></tr> 651<tr><td>v12.0.0</td> 652<td><p>Internal properties no longer appear in the context argument of a custom inspection function.</p></td></tr> 653<tr><td>v11.11.0</td> 654<td><p>The <code>compact</code> option accepts numbers for a new output mode.</p></td></tr> 655<tr><td>v11.7.0</td> 656<td><p>ArrayBuffers now also show their binary contents.</p></td></tr> 657<tr><td>v11.5.0</td> 658<td><p>The <code>getters</code> option is supported now.</p></td></tr> 659<tr><td>v11.4.0</td> 660<td><p>The <code>depth</code> default changed back to <code>2</code>.</p></td></tr> 661<tr><td>v11.0.0</td> 662<td><p>The <code>depth</code> default changed to <code>20</code>.</p></td></tr> 663<tr><td>v11.0.0</td> 664<td><p>The inspection output is now limited to about 128 MB. Data above that size will not be fully inspected.</p></td></tr> 665<tr><td>v10.12.0</td> 666<td><p>The <code>sorted</code> option is supported now.</p></td></tr> 667<tr><td>v10.6.0</td> 668<td><p>Inspecting linked lists and similar objects is now possible up to the maximum call stack size.</p></td></tr> 669<tr><td>v10.0.0</td> 670<td><p>The <code>WeakMap</code> and <code>WeakSet</code> entries can now be inspected as well.</p></td></tr> 671<tr><td>v9.9.0</td> 672<td><p>The <code>compact</code> option is supported now.</p></td></tr> 673<tr><td>v6.6.0</td> 674<td><p>Custom inspection functions can now return <code>this</code>.</p></td></tr> 675<tr><td>v6.3.0</td> 676<td><p>The <code>breakLength</code> option is supported now.</p></td></tr> 677<tr><td>v6.1.0</td> 678<td><p>The <code>maxArrayLength</code> option is supported now; in particular, long arrays are truncated by default.</p></td></tr> 679<tr><td>v6.1.0</td> 680<td><p>The <code>showProxy</code> option is supported now.</p></td></tr> 681<tr><td>v0.3.0</td> 682<td><p><span>Added in: v0.3.0</span></p></td></tr> 683</tbody></table> 684</details> 685</div> 686<ul> 687<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Any JavaScript primitive or <code>Object</code>.</li> 688<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 689<ul> 690<li><code>showHidden</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, <code>object</code>'s non-enumerable symbols and 691properties are included in the formatted result. <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap"><code>WeakMap</code></a> and 692<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet"><code>WeakSet</code></a> entries are also included as well as user defined prototype 693properties (excluding method properties). <strong>Default:</strong> <code>false</code>.</li> 694<li><code>depth</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the number of times to recurse while formatting 695<code>object</code>. This is useful for inspecting large objects. To recurse up to 696the maximum call stack size pass <code>Infinity</code> or <code>null</code>. 697<strong>Default:</strong> <code>2</code>.</li> 698<li><code>colors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, the output is styled with ANSI color 699codes. Colors are customizable. See <a href="#util_customizing_util_inspect_colors">Customizing <code>util.inspect</code> colors</a>. 700<strong>Default:</strong> <code>false</code>.</li> 701<li><code>customInspect</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>false</code>, 702<code>[util.inspect.custom](depth, opts)</code> functions are not invoked. 703<strong>Default:</strong> <code>true</code>.</li> 704<li><code>showProxy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, <code>Proxy</code> inspection includes 705the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy#Terminology"><code>target</code> and <code>handler</code></a> objects. <strong>Default:</strong> <code>false</code>.</li> 706<li><code>maxArrayLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the maximum number of <code>Array</code>, 707<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap"><code>WeakMap</code></a> and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet"><code>WeakSet</code></a> elements to include when 708formatting. Set to <code>null</code> or <code>Infinity</code> to show all elements. Set to <code>0</code> or 709negative to show no elements. <strong>Default:</strong> <code>100</code>.</li> 710<li><code>maxStringLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the maximum number of characters to 711include when formatting. Set to <code>null</code> or <code>Infinity</code> to show all elements. 712Set to <code>0</code> or negative to show no characters. <strong>Default:</strong> <code>Infinity</code>.</li> 713<li><code>breakLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The length at which input values are split across 714multiple lines. Set to <code>Infinity</code> to format the input as a single line 715(in combination with <code>compact</code> set to <code>true</code> or any number >= <code>1</code>). 716<strong>Default:</strong> <code>80</code>.</li> 717<li><code>compact</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Setting this to <code>false</code> causes each object key 718to be displayed on a new line. It will also add new lines to text that is 719longer than <code>breakLength</code>. If set to a number, the most <code>n</code> inner elements 720are united on a single line as long as all properties fit into 721<code>breakLength</code>. Short array elements are also grouped together. No 722text will be reduced below 16 characters, no matter the <code>breakLength</code> size. 723For more information, see the example below. <strong>Default:</strong> <code>3</code>.</li> 724<li><code>sorted</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> If set to <code>true</code> or a function, all properties 725of an object, and <code>Set</code> and <code>Map</code> entries are sorted in the resulting 726string. If set to <code>true</code> the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort">default sort</a> is used. If set to a function, 727it is used as a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort#Parameters">compare function</a>.</li> 728<li><code>getters</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If set to <code>true</code>, getters are inspected. If set 729to <code>'get'</code>, only getters without a corresponding setter are inspected. If 730set to <code>'set'</code>, only getters with a corresponding setter are inspected. 731This might cause side effects depending on the getter function. 732<strong>Default:</strong> <code>false</code>.</li> 733</ul> 734</li> 735<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The representation of <code>object</code>.</li> 736</ul> 737<p>The <code>util.inspect()</code> method returns a string representation of <code>object</code> that is 738intended for debugging. The output of <code>util.inspect</code> may change at any time 739and should not be depended upon programmatically. Additional <code>options</code> may be 740passed that alter the result. 741<code>util.inspect()</code> will use the constructor's name and/or <code>@@toStringTag</code> to make 742an identifiable tag for an inspected value.</p> 743<pre><code class="language-js"><span class="hljs-keyword">class</span> <span class="hljs-title class_">Foo</span> { 744 get [<span class="hljs-title class_">Symbol</span>.<span class="hljs-property">toStringTag</span>]() { 745 <span class="hljs-keyword">return</span> <span class="hljs-string">'bar'</span>; 746 } 747} 748 749<span class="hljs-keyword">class</span> <span class="hljs-title class_">Bar</span> {} 750 751<span class="hljs-keyword">const</span> baz = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">create</span>(<span class="hljs-literal">null</span>, { [<span class="hljs-title class_">Symbol</span>.<span class="hljs-property">toStringTag</span>]: { <span class="hljs-attr">value</span>: <span class="hljs-string">'foo'</span> } }); 752 753util.<span class="hljs-title function_">inspect</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Foo</span>()); <span class="hljs-comment">// 'Foo [bar] {}'</span> 754util.<span class="hljs-title function_">inspect</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Bar</span>()); <span class="hljs-comment">// 'Bar {}'</span> 755util.<span class="hljs-title function_">inspect</span>(baz); <span class="hljs-comment">// '[foo] {}'</span></code></pre> 756<p>Circular references point to their anchor by using a reference index:</p> 757<pre><code class="language-js"><span class="hljs-keyword">const</span> { inspect } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 758 759<span class="hljs-keyword">const</span> obj = {}; 760obj.<span class="hljs-property">a</span> = [obj]; 761obj.<span class="hljs-property">b</span> = {}; 762obj.<span class="hljs-property">b</span>.<span class="hljs-property">inner</span> = obj.<span class="hljs-property">b</span>; 763obj.<span class="hljs-property">b</span>.<span class="hljs-property">obj</span> = obj; 764 765<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">inspect</span>(obj)); 766<span class="hljs-comment">// <ref *1> {</span> 767<span class="hljs-comment">// a: [ [Circular *1] ],</span> 768<span class="hljs-comment">// b: <ref *2> { inner: [Circular *2], obj: [Circular *1] }</span> 769<span class="hljs-comment">// }</span></code></pre> 770<p>The following example inspects all properties of the <code>util</code> object:</p> 771<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 772 773<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(util.<span class="hljs-title function_">inspect</span>(util, { <span class="hljs-attr">showHidden</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">depth</span>: <span class="hljs-literal">null</span> }));</code></pre> 774<p>The following example highlights the effect of the <code>compact</code> option:</p> 775<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 776 777<span class="hljs-keyword">const</span> o = { 778 <span class="hljs-attr">a</span>: [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, [[ 779 <span class="hljs-string">'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do '</span> + 780 <span class="hljs-string">'eiusmod tempor incididunt ut labore et dolore magna aliqua.'</span>, 781 <span class="hljs-string">'test'</span>, 782 <span class="hljs-string">'foo'</span>]], <span class="hljs-number">4</span>], 783 <span class="hljs-attr">b</span>: <span class="hljs-keyword">new</span> <span class="hljs-title class_">Map</span>([[<span class="hljs-string">'za'</span>, <span class="hljs-number">1</span>], [<span class="hljs-string">'zb'</span>, <span class="hljs-string">'test'</span>]]) 784}; 785<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(util.<span class="hljs-title function_">inspect</span>(o, { <span class="hljs-attr">compact</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">depth</span>: <span class="hljs-number">5</span>, <span class="hljs-attr">breakLength</span>: <span class="hljs-number">80</span> })); 786 787<span class="hljs-comment">// { a:</span> 788<span class="hljs-comment">// [ 1,</span> 789<span class="hljs-comment">// 2,</span> 790<span class="hljs-comment">// [ [ 'Lorem ipsum dolor sit amet, consectetur [...]', // A long line</span> 791<span class="hljs-comment">// 'test',</span> 792<span class="hljs-comment">// 'foo' ] ],</span> 793<span class="hljs-comment">// 4 ],</span> 794<span class="hljs-comment">// b: Map(2) { 'za' => 1, 'zb' => 'test' } }</span> 795 796<span class="hljs-comment">// Setting `compact` to false changes the output to be more reader friendly.</span> 797<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(util.<span class="hljs-title function_">inspect</span>(o, { <span class="hljs-attr">compact</span>: <span class="hljs-literal">false</span>, <span class="hljs-attr">depth</span>: <span class="hljs-number">5</span>, <span class="hljs-attr">breakLength</span>: <span class="hljs-number">80</span> })); 798 799<span class="hljs-comment">// {</span> 800<span class="hljs-comment">// a: [</span> 801<span class="hljs-comment">// 1,</span> 802<span class="hljs-comment">// 2,</span> 803<span class="hljs-comment">// [</span> 804<span class="hljs-comment">// [</span> 805<span class="hljs-comment">// 'Lorem ipsum dolor sit amet, consectetur ' +</span> 806<span class="hljs-comment">// 'adipiscing elit, sed do eiusmod tempor ' +</span> 807<span class="hljs-comment">// 'incididunt ut labore et dolore magna ' +</span> 808<span class="hljs-comment">// 'aliqua.,</span> 809<span class="hljs-comment">// 'test',</span> 810<span class="hljs-comment">// 'foo'</span> 811<span class="hljs-comment">// ]</span> 812<span class="hljs-comment">// ],</span> 813<span class="hljs-comment">// 4</span> 814<span class="hljs-comment">// ],</span> 815<span class="hljs-comment">// b: Map(2) {</span> 816<span class="hljs-comment">// 'za' => 1,</span> 817<span class="hljs-comment">// 'zb' => 'test'</span> 818<span class="hljs-comment">// }</span> 819<span class="hljs-comment">// }</span> 820 821<span class="hljs-comment">// Setting `breakLength` to e.g. 150 will print the "Lorem ipsum" text in a</span> 822<span class="hljs-comment">// single line.</span> 823<span class="hljs-comment">// Reducing the `breakLength` will split the "Lorem ipsum" text in smaller</span> 824<span class="hljs-comment">// chunks.</span></code></pre> 825<p>The <code>showHidden</code> option allows <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap"><code>WeakMap</code></a> and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet"><code>WeakSet</code></a> entries to be 826inspected. If there are more entries than <code>maxArrayLength</code>, there is no 827guarantee which entries are displayed. That means retrieving the same 828<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet"><code>WeakSet</code></a> entries twice may result in different output. Furthermore, entries 829with no remaining strong references may be garbage collected at any time.</p> 830<pre><code class="language-js"><span class="hljs-keyword">const</span> { inspect } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 831 832<span class="hljs-keyword">const</span> obj = { <span class="hljs-attr">a</span>: <span class="hljs-number">1</span> }; 833<span class="hljs-keyword">const</span> obj2 = { <span class="hljs-attr">b</span>: <span class="hljs-number">2</span> }; 834<span class="hljs-keyword">const</span> weakSet = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakSet</span>([obj, obj2]); 835 836<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">inspect</span>(weakSet, { <span class="hljs-attr">showHidden</span>: <span class="hljs-literal">true</span> })); 837<span class="hljs-comment">// WeakSet { { a: 1 }, { b: 2 } }</span></code></pre> 838<p>The <code>sorted</code> option ensures that an object's property insertion order does not 839impact the result of <code>util.inspect()</code>.</p> 840<pre><code class="language-js"><span class="hljs-keyword">const</span> { inspect } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 841<span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'assert'</span>); 842 843<span class="hljs-keyword">const</span> o1 = { 844 <span class="hljs-attr">b</span>: [<span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">1</span>], 845 <span class="hljs-attr">a</span>: <span class="hljs-string">'`a` comes before `b`'</span>, 846 <span class="hljs-attr">c</span>: <span class="hljs-keyword">new</span> <span class="hljs-title class_">Set</span>([<span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">1</span>]) 847}; 848<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">inspect</span>(o1, { <span class="hljs-attr">sorted</span>: <span class="hljs-literal">true</span> })); 849<span class="hljs-comment">// { a: '`a` comes before `b`', b: [ 2, 3, 1 ], c: Set(3) { 1, 2, 3 } }</span> 850<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">inspect</span>(o1, { <span class="hljs-attr">sorted</span>: <span class="hljs-function">(<span class="hljs-params">a, b</span>) =></span> b.<span class="hljs-title function_">localeCompare</span>(a) })); 851<span class="hljs-comment">// { c: Set(3) { 3, 2, 1 }, b: [ 2, 3, 1 ], a: '`a` comes before `b`' }</span> 852 853<span class="hljs-keyword">const</span> o2 = { 854 <span class="hljs-attr">c</span>: <span class="hljs-keyword">new</span> <span class="hljs-title class_">Set</span>([<span class="hljs-number">2</span>, <span class="hljs-number">1</span>, <span class="hljs-number">3</span>]), 855 <span class="hljs-attr">a</span>: <span class="hljs-string">'`a` comes before `b`'</span>, 856 <span class="hljs-attr">b</span>: [<span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">1</span>] 857}; 858assert.<span class="hljs-property">strict</span>.<span class="hljs-title function_">equal</span>( 859 <span class="hljs-title function_">inspect</span>(o1, { <span class="hljs-attr">sorted</span>: <span class="hljs-literal">true</span> }), 860 <span class="hljs-title function_">inspect</span>(o2, { <span class="hljs-attr">sorted</span>: <span class="hljs-literal">true</span> }) 861);</code></pre> 862<p><code>util.inspect()</code> is a synchronous method intended for debugging. Its maximum 863output length is approximately 128 MB. Inputs that result in longer output will 864be truncated.</p> 865<h4>Customizing <code>util.inspect</code> colors<span><a class="mark" href="#util_customizing_util_inspect_colors" id="util_customizing_util_inspect_colors">#</a></span></h4> 866 867<p>Color output (if enabled) of <code>util.inspect</code> is customizable globally 868via the <code>util.inspect.styles</code> and <code>util.inspect.colors</code> properties.</p> 869<p><code>util.inspect.styles</code> is a map associating a style name to a color from 870<code>util.inspect.colors</code>.</p> 871<p>The default styles and associated colors are:</p> 872<ul> 873<li><code>bigint</code>: <code>yellow</code></li> 874<li><code>boolean</code>: <code>yellow</code></li> 875<li><code>date</code>: <code>magenta</code></li> 876<li><code>module</code>: <code>underline</code></li> 877<li><code>name</code>: (no styling)</li> 878<li><code>null</code>: <code>bold</code></li> 879<li><code>number</code>: <code>yellow</code></li> 880<li><code>regexp</code>: <code>red</code></li> 881<li><code>special</code>: <code>cyan</code> (e.g., <code>Proxies</code>)</li> 882<li><code>string</code>: <code>green</code></li> 883<li><code>symbol</code>: <code>green</code></li> 884<li><code>undefined</code>: <code>grey</code></li> 885</ul> 886<p>Color styling uses ANSI control codes that may not be supported on all 887terminals. To verify color support use <a href="tty.html#tty_writestream_hascolors_count_env"><code>tty.hasColors()</code></a>.</p> 888<p>Predefined control codes are listed below (grouped as "Modifiers", "Foreground 889colors", and "Background colors").</p> 890<h5>Modifiers<span><a class="mark" href="#util_modifiers" id="util_modifiers">#</a></span></h5> 891<p>Modifier support varies throughout different terminals. They will mostly be 892ignored, if not supported.</p> 893<ul> 894<li><code>reset</code> - Resets all (color) modifiers to their defaults</li> 895<li><strong>bold</strong> - Make text bold</li> 896<li><em>italic</em> - Make text italic</li> 897<li><span style="border-bottom: 1px;">underline</span> - Make text underlined</li> 898<li><del>strikethrough</del> - Puts a horizontal line through the center of the text 899(Alias: <code>strikeThrough</code>, <code>crossedout</code>, <code>crossedOut</code>)</li> 900<li><code>hidden</code> - Prints the text, but makes it invisible (Alias: conceal)</li> 901<li><span style="opacity: 0.5;">dim</span> - Decreased color intensity (Alias: 902<code>faint</code>)</li> 903<li><span style="border-top: 1px">overlined</span> - Make text overlined</li> 904<li>blink - Hides and shows the text in an interval</li> 905<li><span style="filter: invert(100%)">inverse</span> - Swap foreground and 906background colors (Alias: <code>swapcolors</code>, <code>swapColors</code>)</li> 907<li><span style="border-bottom: 1px double;">doubleunderline</span> - Make text 908double underlined (Alias: <code>doubleUnderline</code>)</li> 909<li><span style="border: 1px">framed</span> - Draw a frame around the text</li> 910</ul> 911<h5>Foreground colors<span><a class="mark" href="#util_foreground_colors" id="util_foreground_colors">#</a></span></h5> 912<ul> 913<li><code>black</code></li> 914<li><code>red</code></li> 915<li><code>green</code></li> 916<li><code>yellow</code></li> 917<li><code>blue</code></li> 918<li><code>magenta</code></li> 919<li><code>cyan</code></li> 920<li><code>white</code></li> 921<li><code>gray</code> (alias: <code>grey</code>, <code>blackBright</code>)</li> 922<li><code>redBright</code></li> 923<li><code>greenBright</code></li> 924<li><code>yellowBright</code></li> 925<li><code>blueBright</code></li> 926<li><code>magentaBright</code></li> 927<li><code>cyanBright</code></li> 928<li><code>whiteBright</code></li> 929</ul> 930<h5>Background colors<span><a class="mark" href="#util_background_colors" id="util_background_colors">#</a></span></h5> 931<ul> 932<li><code>bgBlack</code></li> 933<li><code>bgRed</code></li> 934<li><code>bgGreen</code></li> 935<li><code>bgYellow</code></li> 936<li><code>bgBlue</code></li> 937<li><code>bgMagenta</code></li> 938<li><code>bgCyan</code></li> 939<li><code>bgWhite</code></li> 940<li><code>bgGray</code> (alias: <code>bgGrey</code>, <code>bgBlackBright</code>)</li> 941<li><code>bgRedBright</code></li> 942<li><code>bgGreenBright</code></li> 943<li><code>bgYellowBright</code></li> 944<li><code>bgBlueBright</code></li> 945<li><code>bgMagentaBright</code></li> 946<li><code>bgCyanBright</code></li> 947<li><code>bgWhiteBright</code></li> 948</ul> 949<h4>Custom inspection functions on objects<span><a class="mark" href="#util_custom_inspection_functions_on_objects" id="util_custom_inspection_functions_on_objects">#</a></span></h4> 950 951<p>Objects may also define their own 952<a href="#util_util_inspect_custom"><code>[util.inspect.custom](depth, opts)</code></a> function, 953which <code>util.inspect()</code> will invoke and use the result of when inspecting 954the object:</p> 955<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 956 957<span class="hljs-keyword">class</span> <span class="hljs-title class_">Box</span> { 958 <span class="hljs-title function_">constructor</span>(<span class="hljs-params">value</span>) { 959 <span class="hljs-variable language_">this</span>.<span class="hljs-property">value</span> = value; 960 } 961 962 [util.<span class="hljs-property">inspect</span>.<span class="hljs-property">custom</span>](depth, options) { 963 <span class="hljs-keyword">if</span> (depth < <span class="hljs-number">0</span>) { 964 <span class="hljs-keyword">return</span> options.<span class="hljs-title function_">stylize</span>(<span class="hljs-string">'[Box]'</span>, <span class="hljs-string">'special'</span>); 965 } 966 967 <span class="hljs-keyword">const</span> newOptions = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">assign</span>({}, options, { 968 <span class="hljs-attr">depth</span>: options.<span class="hljs-property">depth</span> === <span class="hljs-literal">null</span> ? <span class="hljs-literal">null</span> : options.<span class="hljs-property">depth</span> - <span class="hljs-number">1</span> 969 }); 970 971 <span class="hljs-comment">// Five space padding because that's the size of "Box< ".</span> 972 <span class="hljs-keyword">const</span> padding = <span class="hljs-string">' '</span>.<span class="hljs-title function_">repeat</span>(<span class="hljs-number">5</span>); 973 <span class="hljs-keyword">const</span> inner = util.<span class="hljs-title function_">inspect</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">value</span>, newOptions) 974 .<span class="hljs-title function_">replace</span>(<span class="hljs-regexp">/\n/g</span>, <span class="hljs-string">`\n<span class="hljs-subst">${padding}</span>`</span>); 975 <span class="hljs-keyword">return</span> <span class="hljs-string">`<span class="hljs-subst">${options.stylize(<span class="hljs-string">'Box'</span>, <span class="hljs-string">'special'</span>)}</span>< <span class="hljs-subst">${inner}</span> >`</span>; 976 } 977} 978 979<span class="hljs-keyword">const</span> box = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Box</span>(<span class="hljs-literal">true</span>); 980 981util.<span class="hljs-title function_">inspect</span>(box); 982<span class="hljs-comment">// Returns: "Box< true >"</span></code></pre> 983<p>Custom <code>[util.inspect.custom](depth, opts)</code> functions typically return a string 984but may return a value of any type that will be formatted accordingly by 985<code>util.inspect()</code>.</p> 986<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 987 988<span class="hljs-keyword">const</span> obj = { <span class="hljs-attr">foo</span>: <span class="hljs-string">'this will not show up in the inspect() output'</span> }; 989obj[util.<span class="hljs-property">inspect</span>.<span class="hljs-property">custom</span>] = <span class="hljs-function">(<span class="hljs-params">depth</span>) =></span> { 990 <span class="hljs-keyword">return</span> { <span class="hljs-attr">bar</span>: <span class="hljs-string">'baz'</span> }; 991}; 992 993util.<span class="hljs-title function_">inspect</span>(obj); 994<span class="hljs-comment">// Returns: "{ bar: 'baz' }"</span></code></pre> 995<h4><code>util.inspect.custom</code><span><a class="mark" href="#util_util_inspect_custom" id="util_util_inspect_custom">#</a></span></h4> 996<div class="api_metadata"> 997<details class="changelog"><summary>History</summary> 998<table> 999<tbody><tr><th>Version</th><th>Changes</th></tr> 1000<tr><td>v10.12.0</td> 1001<td><p>This is now defined as a shared symbol.</p></td></tr> 1002<tr><td>v6.6.0</td> 1003<td><p><span>Added in: v6.6.0</span></p></td></tr> 1004</tbody></table> 1005</details> 1006</div> 1007<ul> 1008<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> that can be used to declare custom inspect functions.</li> 1009</ul> 1010<p>In addition to being accessible through <code>util.inspect.custom</code>, this 1011symbol is <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/for">registered globally</a> and can be 1012accessed in any environment as <code>Symbol.for('nodejs.util.inspect.custom')</code>.</p> 1013<pre><code class="language-js"><span class="hljs-keyword">const</span> inspect = <span class="hljs-title class_">Symbol</span>.<span class="hljs-title function_">for</span>(<span class="hljs-string">'nodejs.util.inspect.custom'</span>); 1014 1015<span class="hljs-keyword">class</span> <span class="hljs-title class_">Password</span> { 1016 <span class="hljs-title function_">constructor</span>(<span class="hljs-params">value</span>) { 1017 <span class="hljs-variable language_">this</span>.<span class="hljs-property">value</span> = value; 1018 } 1019 1020 <span class="hljs-title function_">toString</span>(<span class="hljs-params"></span>) { 1021 <span class="hljs-keyword">return</span> <span class="hljs-string">'xxxxxxxx'</span>; 1022 } 1023 1024 [inspect]() { 1025 <span class="hljs-keyword">return</span> <span class="hljs-string">`Password <<span class="hljs-subst">${<span class="hljs-variable language_">this</span>.toString()}</span>>`</span>; 1026 } 1027} 1028 1029<span class="hljs-keyword">const</span> password = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Password</span>(<span class="hljs-string">'r0sebud'</span>); 1030<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(password); 1031<span class="hljs-comment">// Prints Password <xxxxxxxx></span></code></pre> 1032<p>See <a href="#util_custom_inspection_functions_on_objects">Custom inspection functions on Objects</a> for more details.</p> 1033<h4><code>util.inspect.defaultOptions</code><span><a class="mark" href="#util_util_inspect_defaultoptions" id="util_util_inspect_defaultoptions">#</a></span></h4> 1034<div class="api_metadata"> 1035<span>Added in: v6.4.0</span> 1036</div> 1037<p>The <code>defaultOptions</code> value allows customization of the default options used by 1038<code>util.inspect</code>. This is useful for functions like <code>console.log</code> or 1039<code>util.format</code> which implicitly call into <code>util.inspect</code>. It shall be set to an 1040object containing one or more valid <a href="#util_util_inspect_object_options"><code>util.inspect()</code></a> options. Setting 1041option properties directly is also supported.</p> 1042<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 1043<span class="hljs-keyword">const</span> arr = <span class="hljs-title class_">Array</span>(<span class="hljs-number">101</span>).<span class="hljs-title function_">fill</span>(<span class="hljs-number">0</span>); 1044 1045<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(arr); <span class="hljs-comment">// Logs the truncated array</span> 1046util.<span class="hljs-property">inspect</span>.<span class="hljs-property">defaultOptions</span>.<span class="hljs-property">maxArrayLength</span> = <span class="hljs-literal">null</span>; 1047<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(arr); <span class="hljs-comment">// logs the full array</span></code></pre> 1048</section><section><h3><code>util.isDeepStrictEqual(val1, val2)</code><span><a class="mark" href="#util_util_isdeepstrictequal_val1_val2" id="util_util_isdeepstrictequal_val1_val2">#</a></span></h3> 1049<div class="api_metadata"> 1050<span>Added in: v9.0.0</span> 1051</div> 1052<ul> 1053<li><code>val1</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1054<li><code>val2</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1055<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1056</ul> 1057<p>Returns <code>true</code> if there is deep strict equality between <code>val1</code> and <code>val2</code>. 1058Otherwise, returns <code>false</code>.</p> 1059<p>See <a href="assert.html#assert_assert_deepstrictequal_actual_expected_message"><code>assert.deepStrictEqual()</code></a> for more information about deep strict 1060equality.</p> 1061</section><section><h3><code>util.promisify(original)</code><span><a class="mark" href="#util_util_promisify_original" id="util_util_promisify_original">#</a></span></h3> 1062<div class="api_metadata"> 1063<span>Added in: v8.0.0</span> 1064</div> 1065<ul> 1066<li><code>original</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1067<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1068</ul> 1069<p>Takes a function following the common error-first callback style, i.e. taking 1070an <code>(err, value) => ...</code> callback as the last argument, and returns a version 1071that returns promises.</p> 1072<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 1073<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'fs'</span>); 1074 1075<span class="hljs-keyword">const</span> stat = util.<span class="hljs-title function_">promisify</span>(fs.<span class="hljs-property">stat</span>); 1076<span class="hljs-title function_">stat</span>(<span class="hljs-string">'.'</span>).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">stats</span>) =></span> { 1077 <span class="hljs-comment">// Do something with `stats`</span> 1078}).<span class="hljs-title function_">catch</span>(<span class="hljs-function">(<span class="hljs-params">error</span>) =></span> { 1079 <span class="hljs-comment">// Handle the error.</span> 1080});</code></pre> 1081<p>Or, equivalently using <code>async function</code>s:</p> 1082<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 1083<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'fs'</span>); 1084 1085<span class="hljs-keyword">const</span> stat = util.<span class="hljs-title function_">promisify</span>(fs.<span class="hljs-property">stat</span>); 1086 1087<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">callStat</span>(<span class="hljs-params"></span>) { 1088 <span class="hljs-keyword">const</span> stats = <span class="hljs-keyword">await</span> <span class="hljs-title function_">stat</span>(<span class="hljs-string">'.'</span>); 1089 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`This directory is owned by <span class="hljs-subst">${stats.uid}</span>`</span>); 1090}</code></pre> 1091<p>If there is an <code>original[util.promisify.custom]</code> property present, <code>promisify</code> 1092will return its value, see <a href="#util_custom_promisified_functions">Custom promisified functions</a>.</p> 1093<p><code>promisify()</code> assumes that <code>original</code> is a function taking a callback as its 1094final argument in all cases. If <code>original</code> is not a function, <code>promisify()</code> 1095will throw an error. If <code>original</code> is a function but its last argument is not 1096an error-first callback, it will still be passed an error-first 1097callback as its last argument.</p> 1098<p>Using <code>promisify()</code> on class methods or other methods that use <code>this</code> may not 1099work as expected unless handled specially:</p> 1100<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 1101 1102<span class="hljs-keyword">class</span> <span class="hljs-title class_">Foo</span> { 1103 <span class="hljs-title function_">constructor</span>(<span class="hljs-params"></span>) { 1104 <span class="hljs-variable language_">this</span>.<span class="hljs-property">a</span> = <span class="hljs-number">42</span>; 1105 } 1106 1107 <span class="hljs-title function_">bar</span>(<span class="hljs-params">callback</span>) { 1108 <span class="hljs-title function_">callback</span>(<span class="hljs-literal">null</span>, <span class="hljs-variable language_">this</span>.<span class="hljs-property">a</span>); 1109 } 1110} 1111 1112<span class="hljs-keyword">const</span> foo = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Foo</span>(); 1113 1114<span class="hljs-keyword">const</span> naiveBar = util.<span class="hljs-title function_">promisify</span>(foo.<span class="hljs-property">bar</span>); 1115<span class="hljs-comment">// TypeError: Cannot read property 'a' of undefined</span> 1116<span class="hljs-comment">// naiveBar().then(a => console.log(a));</span> 1117 1118naiveBar.<span class="hljs-title function_">call</span>(foo).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">a</span>) =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(a)); <span class="hljs-comment">// '42'</span> 1119 1120<span class="hljs-keyword">const</span> bindBar = naiveBar.<span class="hljs-title function_">bind</span>(foo); 1121<span class="hljs-title function_">bindBar</span>().<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">a</span>) =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(a)); <span class="hljs-comment">// '42'</span></code></pre> 1122<h4>Custom promisified functions<span><a class="mark" href="#util_custom_promisified_functions" id="util_custom_promisified_functions">#</a></span></h4> 1123<p>Using the <code>util.promisify.custom</code> symbol one can override the return value of 1124<a href="#util_util_promisify_original"><code>util.promisify()</code></a>:</p> 1125<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 1126 1127<span class="hljs-keyword">function</span> <span class="hljs-title function_">doSomething</span>(<span class="hljs-params">foo, callback</span>) { 1128 <span class="hljs-comment">// ...</span> 1129} 1130 1131doSomething[util.<span class="hljs-property">promisify</span>.<span class="hljs-property">custom</span>] = <span class="hljs-function">(<span class="hljs-params">foo</span>) =></span> { 1132 <span class="hljs-keyword">return</span> <span class="hljs-title function_">getPromiseSomehow</span>(); 1133}; 1134 1135<span class="hljs-keyword">const</span> promisified = util.<span class="hljs-title function_">promisify</span>(doSomething); 1136<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(promisified === doSomething[util.<span class="hljs-property">promisify</span>.<span class="hljs-property">custom</span>]); 1137<span class="hljs-comment">// prints 'true'</span></code></pre> 1138<p>This can be useful for cases where the original function does not follow the 1139standard format of taking an error-first callback as the last argument.</p> 1140<p>For example, with a function that takes in 1141<code>(foo, onSuccessCallback, onErrorCallback)</code>:</p> 1142<pre><code class="language-js">doSomething[util.<span class="hljs-property">promisify</span>.<span class="hljs-property">custom</span>] = <span class="hljs-function">(<span class="hljs-params">foo</span>) =></span> { 1143 <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Promise</span>(<span class="hljs-function">(<span class="hljs-params">resolve, reject</span>) =></span> { 1144 <span class="hljs-title function_">doSomething</span>(foo, resolve, reject); 1145 }); 1146};</code></pre> 1147<p>If <code>promisify.custom</code> is defined but is not a function, <code>promisify()</code> will 1148throw an error.</p> 1149<h4><code>util.promisify.custom</code><span><a class="mark" href="#util_util_promisify_custom" id="util_util_promisify_custom">#</a></span></h4> 1150<div class="api_metadata"> 1151<details class="changelog"><summary>History</summary> 1152<table> 1153<tbody><tr><th>Version</th><th>Changes</th></tr> 1154<tr><td>v13.12.0, v12.16.2</td> 1155<td><p>This is now defined as a shared symbol.</p></td></tr> 1156<tr><td>v8.0.0</td> 1157<td><p><span>Added in: v8.0.0</span></p></td></tr> 1158</tbody></table> 1159</details> 1160</div> 1161<ul> 1162<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Symbol_type" class="type"><symbol></a> that can be used to declare custom promisified variants of functions, 1163see <a href="#util_custom_promisified_functions">Custom promisified functions</a>.</li> 1164</ul> 1165<p>In addition to being accessible through <code>util.promisify.custom</code>, this 1166symbol is <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/for">registered globally</a> and can be 1167accessed in any environment as <code>Symbol.for('nodejs.util.promisify.custom')</code>.</p> 1168<p>For example, with a function that takes in 1169<code>(foo, onSuccessCallback, onErrorCallback)</code>:</p> 1170<pre><code class="language-js"><span class="hljs-keyword">const</span> kCustomPromisifiedSymbol = <span class="hljs-title class_">Symbol</span>.<span class="hljs-title function_">for</span>(<span class="hljs-string">'nodejs.util.promisify.custom'</span>); 1171 1172doSomething[kCustomPromisifiedSymbol] = <span class="hljs-function">(<span class="hljs-params">foo</span>) =></span> { 1173 <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Promise</span>(<span class="hljs-function">(<span class="hljs-params">resolve, reject</span>) =></span> { 1174 <span class="hljs-title function_">doSomething</span>(foo, resolve, reject); 1175 }); 1176};</code></pre> 1177</section><section><h3>Class: <code>util.TextDecoder</code><span><a class="mark" href="#util_class_util_textdecoder" id="util_class_util_textdecoder">#</a></span></h3> 1178<div class="api_metadata"> 1179<span>Added in: v8.3.0</span> 1180</div> 1181<p>An implementation of the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> <code>TextDecoder</code> API.</p> 1182<pre><code class="language-js"><span class="hljs-keyword">const</span> decoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TextDecoder</span>(<span class="hljs-string">'shift_jis'</span>); 1183<span class="hljs-keyword">let</span> string = <span class="hljs-string">''</span>; 1184<span class="hljs-keyword">let</span> buffer; 1185<span class="hljs-keyword">while</span> (buffer = <span class="hljs-title function_">getNextChunkSomehow</span>()) { 1186 string += decoder.<span class="hljs-title function_">decode</span>(buffer, { <span class="hljs-attr">stream</span>: <span class="hljs-literal">true</span> }); 1187} 1188string += decoder.<span class="hljs-title function_">decode</span>(); <span class="hljs-comment">// end-of-stream</span></code></pre> 1189<h4>WHATWG supported encodings<span><a class="mark" href="#util_whatwg_supported_encodings" id="util_whatwg_supported_encodings">#</a></span></h4> 1190<p>Per the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a>, the encodings supported by the 1191<code>TextDecoder</code> API are outlined in the tables below. For each encoding, 1192one or more aliases may be used.</p> 1193<p>Different Node.js build configurations support different sets of encodings. 1194(see <a href="intl.html">Internationalization</a>)</p> 1195<h5>Encodings supported by default (with full ICU data)<span><a class="mark" href="#util_encodings_supported_by_default_with_full_icu_data" id="util_encodings_supported_by_default_with_full_icu_data">#</a></span></h5> 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341<table><thead><tr><th>Encoding</th><th>Aliases</th></tr></thead><tbody><tr><td><code>'ibm866'</code></td><td><code>'866'</code>, <code>'cp866'</code>, <code>'csibm866'</code></td></tr><tr><td><code>'iso-8859-2'</code></td><td><code>'csisolatin2'</code>, <code>'iso-ir-101'</code>, <code>'iso8859-2'</code>, <code>'iso88592'</code>, <code>'iso_8859-2'</code>, <code>'iso_8859-2:1987'</code>, <code>'l2'</code>, <code>'latin2'</code></td></tr><tr><td><code>'iso-8859-3'</code></td><td><code>'csisolatin3'</code>, <code>'iso-ir-109'</code>, <code>'iso8859-3'</code>, <code>'iso88593'</code>, <code>'iso_8859-3'</code>, <code>'iso_8859-3:1988'</code>, <code>'l3'</code>, <code>'latin3'</code></td></tr><tr><td><code>'iso-8859-4'</code></td><td><code>'csisolatin4'</code>, <code>'iso-ir-110'</code>, <code>'iso8859-4'</code>, <code>'iso88594'</code>, <code>'iso_8859-4'</code>, <code>'iso_8859-4:1988'</code>, <code>'l4'</code>, <code>'latin4'</code></td></tr><tr><td><code>'iso-8859-5'</code></td><td><code>'csisolatincyrillic'</code>, <code>'cyrillic'</code>, <code>'iso-ir-144'</code>, <code>'iso8859-5'</code>, <code>'iso88595'</code>, <code>'iso_8859-5'</code>, <code>'iso_8859-5:1988'</code></td></tr><tr><td><code>'iso-8859-6'</code></td><td><code>'arabic'</code>, <code>'asmo-708'</code>, <code>'csiso88596e'</code>, <code>'csiso88596i'</code>, <code>'csisolatinarabic'</code>, <code>'ecma-114'</code>, <code>'iso-8859-6-e'</code>, <code>'iso-8859-6-i'</code>, <code>'iso-ir-127'</code>, <code>'iso8859-6'</code>, <code>'iso88596'</code>, <code>'iso_8859-6'</code>, <code>'iso_8859-6:1987'</code></td></tr><tr><td><code>'iso-8859-7'</code></td><td><code>'csisolatingreek'</code>, <code>'ecma-118'</code>, <code>'elot_928'</code>, <code>'greek'</code>, <code>'greek8'</code>, <code>'iso-ir-126'</code>, <code>'iso8859-7'</code>, <code>'iso88597'</code>, <code>'iso_8859-7'</code>, <code>'iso_8859-7:1987'</code>, <code>'sun_eu_greek'</code></td></tr><tr><td><code>'iso-8859-8'</code></td><td><code>'csiso88598e'</code>, <code>'csisolatinhebrew'</code>, <code>'hebrew'</code>, <code>'iso-8859-8-e'</code>, <code>'iso-ir-138'</code>, <code>'iso8859-8'</code>, <code>'iso88598'</code>, <code>'iso_8859-8'</code>, <code>'iso_8859-8:1988'</code>, <code>'visual'</code></td></tr><tr><td><code>'iso-8859-8-i'</code></td><td><code>'csiso88598i'</code>, <code>'logical'</code></td></tr><tr><td><code>'iso-8859-10'</code></td><td><code>'csisolatin6'</code>, <code>'iso-ir-157'</code>, <code>'iso8859-10'</code>, <code>'iso885910'</code>, <code>'l6'</code>, <code>'latin6'</code></td></tr><tr><td><code>'iso-8859-13'</code></td><td><code>'iso8859-13'</code>, <code>'iso885913'</code></td></tr><tr><td><code>'iso-8859-14'</code></td><td><code>'iso8859-14'</code>, <code>'iso885914'</code></td></tr><tr><td><code>'iso-8859-15'</code></td><td><code>'csisolatin9'</code>, <code>'iso8859-15'</code>, <code>'iso885915'</code>, <code>'iso_8859-15'</code>, <code>'l9'</code></td></tr><tr><td><code>'koi8-r'</code></td><td><code>'cskoi8r'</code>, <code>'koi'</code>, <code>'koi8'</code>, <code>'koi8_r'</code></td></tr><tr><td><code>'koi8-u'</code></td><td><code>'koi8-ru'</code></td></tr><tr><td><code>'macintosh'</code></td><td><code>'csmacintosh'</code>, <code>'mac'</code>, <code>'x-mac-roman'</code></td></tr><tr><td><code>'windows-874'</code></td><td><code>'dos-874'</code>, <code>'iso-8859-11'</code>, <code>'iso8859-11'</code>, <code>'iso885911'</code>, <code>'tis-620'</code></td></tr><tr><td><code>'windows-1250'</code></td><td><code>'cp1250'</code>, <code>'x-cp1250'</code></td></tr><tr><td><code>'windows-1251'</code></td><td><code>'cp1251'</code>, <code>'x-cp1251'</code></td></tr><tr><td><code>'windows-1252'</code></td><td><code>'ansi_x3.4-1968'</code>, <code>'ascii'</code>, <code>'cp1252'</code>, <code>'cp819'</code>, <code>'csisolatin1'</code>, <code>'ibm819'</code>, <code>'iso-8859-1'</code>, <code>'iso-ir-100'</code>, <code>'iso8859-1'</code>, <code>'iso88591'</code>, <code>'iso_8859-1'</code>, <code>'iso_8859-1:1987'</code>, <code>'l1'</code>, <code>'latin1'</code>, <code>'us-ascii'</code>, <code>'x-cp1252'</code></td></tr><tr><td><code>'windows-1253'</code></td><td><code>'cp1253'</code>, <code>'x-cp1253'</code></td></tr><tr><td><code>'windows-1254'</code></td><td><code>'cp1254'</code>, <code>'csisolatin5'</code>, <code>'iso-8859-9'</code>, <code>'iso-ir-148'</code>, <code>'iso8859-9'</code>, <code>'iso88599'</code>, <code>'iso_8859-9'</code>, <code>'iso_8859-9:1989'</code>, <code>'l5'</code>, <code>'latin5'</code>, <code>'x-cp1254'</code></td></tr><tr><td><code>'windows-1255'</code></td><td><code>'cp1255'</code>, <code>'x-cp1255'</code></td></tr><tr><td><code>'windows-1256'</code></td><td><code>'cp1256'</code>, <code>'x-cp1256'</code></td></tr><tr><td><code>'windows-1257'</code></td><td><code>'cp1257'</code>, <code>'x-cp1257'</code></td></tr><tr><td><code>'windows-1258'</code></td><td><code>'cp1258'</code>, <code>'x-cp1258'</code></td></tr><tr><td><code>'x-mac-cyrillic'</code></td><td><code>'x-mac-ukrainian'</code></td></tr><tr><td><code>'gbk'</code></td><td><code>'chinese'</code>, <code>'csgb2312'</code>, <code>'csiso58gb231280'</code>, <code>'gb2312'</code>, <code>'gb_2312'</code>, <code>'gb_2312-80'</code>, <code>'iso-ir-58'</code>, <code>'x-gbk'</code></td></tr><tr><td><code>'gb18030'</code></td><td></td></tr><tr><td><code>'big5'</code></td><td><code>'big5-hkscs'</code>, <code>'cn-big5'</code>, <code>'csbig5'</code>, <code>'x-x-big5'</code></td></tr><tr><td><code>'euc-jp'</code></td><td><code>'cseucpkdfmtjapanese'</code>, <code>'x-euc-jp'</code></td></tr><tr><td><code>'iso-2022-jp'</code></td><td><code>'csiso2022jp'</code></td></tr><tr><td><code>'shift_jis'</code></td><td><code>'csshiftjis'</code>, <code>'ms932'</code>, <code>'ms_kanji'</code>, <code>'shift-jis'</code>, <code>'sjis'</code>, <code>'windows-31j'</code>, <code>'x-sjis'</code></td></tr><tr><td><code>'euc-kr'</code></td><td><code>'cseuckr'</code>, <code>'csksc56011987'</code>, <code>'iso-ir-149'</code>, <code>'korean'</code>, <code>'ks_c_5601-1987'</code>, <code>'ks_c_5601-1989'</code>, <code>'ksc5601'</code>, <code>'ksc_5601'</code>, <code>'windows-949'</code></td></tr></tbody></table> 1342<h5>Encodings supported when Node.js is built with the <code>small-icu</code> option<span><a class="mark" href="#util_encodings_supported_when_node_js_is_built_with_the_small_icu_option" id="util_encodings_supported_when_node_js_is_built_with_the_small_icu_option">#</a></span></h5> 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364<table><thead><tr><th>Encoding</th><th>Aliases</th></tr></thead><tbody><tr><td><code>'utf-8'</code></td><td><code>'unicode-1-1-utf-8'</code>, <code>'utf8'</code></td></tr><tr><td><code>'utf-16le'</code></td><td><code>'utf-16'</code></td></tr><tr><td><code>'utf-16be'</code></td><td></td></tr></tbody></table> 1365<h5>Encodings supported when ICU is disabled<span><a class="mark" href="#util_encodings_supported_when_icu_is_disabled" id="util_encodings_supported_when_icu_is_disabled">#</a></span></h5> 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383<table><thead><tr><th>Encoding</th><th>Aliases</th></tr></thead><tbody><tr><td><code>'utf-8'</code></td><td><code>'unicode-1-1-utf-8'</code>, <code>'utf8'</code></td></tr><tr><td><code>'utf-16le'</code></td><td><code>'utf-16'</code></td></tr></tbody></table> 1384<p>The <code>'iso-8859-16'</code> encoding listed in the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> 1385is not supported.</p> 1386<h4><code>new TextDecoder([encoding[, options]])</code><span><a class="mark" href="#util_new_textdecoder_encoding_options" id="util_new_textdecoder_encoding_options">#</a></span></h4> 1387<div class="api_metadata"> 1388<details class="changelog"><summary>History</summary> 1389<table> 1390<tbody><tr><th>Version</th><th>Changes</th></tr> 1391<tr><td>v11.0.0</td> 1392<td><p>The class is now available on the global object.</p></td></tr> 1393<tr><td>v8.3.0</td> 1394<td><p><span>Added in: v8.3.0</span></p></td></tr> 1395</tbody></table> 1396</details> 1397</div> 1398<ul> 1399<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Identifies the <code>encoding</code> that this <code>TextDecoder</code> instance 1400supports. <strong>Default:</strong> <code>'utf-8'</code>.</li> 1401<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1402<ul> 1403<li><code>fatal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if decoding failures are fatal. 1404This option is not supported when ICU is disabled 1405(see <a href="intl.html">Internationalization</a>). <strong>Default:</strong> <code>false</code>.</li> 1406<li><code>ignoreBOM</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the <code>TextDecoder</code> will include the byte 1407order mark in the decoded result. When <code>false</code>, the byte order mark will 1408be removed from the output. This option is only used when <code>encoding</code> is 1409<code>'utf-8'</code>, <code>'utf-16be'</code> or <code>'utf-16le'</code>. <strong>Default:</strong> <code>false</code>.</li> 1410</ul> 1411</li> 1412</ul> 1413<p>Creates an new <code>TextDecoder</code> instance. The <code>encoding</code> may specify one of the 1414supported encodings or an alias.</p> 1415<p>The <code>TextDecoder</code> class is also available on the global object.</p> 1416<h4><code>textDecoder.decode([input[, options]])</code><span><a class="mark" href="#util_textdecoder_decode_input_options" id="util_textdecoder_decode_input_options">#</a></span></h4> 1417<ul> 1418<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> An <code>ArrayBuffer</code>, <code>DataView</code> or 1419<code>TypedArray</code> instance containing the encoded data.</li> 1420<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1421<ul> 1422<li><code>stream</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if additional chunks of data are expected. 1423<strong>Default:</strong> <code>false</code>.</li> 1424</ul> 1425</li> 1426<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1427</ul> 1428<p>Decodes the <code>input</code> and returns a string. If <code>options.stream</code> is <code>true</code>, any 1429incomplete byte sequences occurring at the end of the <code>input</code> are buffered 1430internally and emitted after the next call to <code>textDecoder.decode()</code>.</p> 1431<p>If <code>textDecoder.fatal</code> is <code>true</code>, decoding errors that occur will result in a 1432<code>TypeError</code> being thrown.</p> 1433<h4><code>textDecoder.encoding</code><span><a class="mark" href="#util_textdecoder_encoding" id="util_textdecoder_encoding">#</a></span></h4> 1434<ul> 1435<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1436</ul> 1437<p>The encoding supported by the <code>TextDecoder</code> instance.</p> 1438<h4><code>textDecoder.fatal</code><span><a class="mark" href="#util_textdecoder_fatal" id="util_textdecoder_fatal">#</a></span></h4> 1439<ul> 1440<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1441</ul> 1442<p>The value will be <code>true</code> if decoding errors result in a <code>TypeError</code> being 1443thrown.</p> 1444<h4><code>textDecoder.ignoreBOM</code><span><a class="mark" href="#util_textdecoder_ignorebom" id="util_textdecoder_ignorebom">#</a></span></h4> 1445<ul> 1446<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1447</ul> 1448<p>The value will be <code>true</code> if the decoding result will include the byte order 1449mark.</p> 1450</section><section><h3>Class: <code>util.TextEncoder</code><span><a class="mark" href="#util_class_util_textencoder" id="util_class_util_textencoder">#</a></span></h3> 1451<div class="api_metadata"> 1452<details class="changelog"><summary>History</summary> 1453<table> 1454<tbody><tr><th>Version</th><th>Changes</th></tr> 1455<tr><td>v11.0.0</td> 1456<td><p>The class is now available on the global object.</p></td></tr> 1457<tr><td>v8.3.0</td> 1458<td><p><span>Added in: v8.3.0</span></p></td></tr> 1459</tbody></table> 1460</details> 1461</div> 1462<p>An implementation of the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> <code>TextEncoder</code> API. All 1463instances of <code>TextEncoder</code> only support UTF-8 encoding.</p> 1464<pre><code class="language-js"><span class="hljs-keyword">const</span> encoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TextEncoder</span>(); 1465<span class="hljs-keyword">const</span> uint8array = encoder.<span class="hljs-title function_">encode</span>(<span class="hljs-string">'this is some data'</span>);</code></pre> 1466<p>The <code>TextEncoder</code> class is also available on the global object.</p> 1467<h4><code>textEncoder.encode([input])</code><span><a class="mark" href="#util_textencoder_encode_input" id="util_textencoder_encode_input">#</a></span></h4> 1468<ul> 1469<li><code>input</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The text to encode. <strong>Default:</strong> an empty string.</li> 1470<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li> 1471</ul> 1472<p>UTF-8 encodes the <code>input</code> string and returns a <code>Uint8Array</code> containing the 1473encoded bytes.</p> 1474<h4><code>textEncoder.encodeInto(src, dest)</code><span><a class="mark" href="#util_textencoder_encodeinto_src_dest" id="util_textencoder_encodeinto_src_dest">#</a></span></h4> 1475<ul> 1476<li><code>src</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The text to encode.</li> 1477<li><code>dest</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> The array to hold the encode result.</li> 1478<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1479<ul> 1480<li><code>read</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The read Unicode code units of src.</li> 1481<li><code>written</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The written UTF-8 bytes of dest.</li> 1482</ul> 1483</li> 1484</ul> 1485<p>UTF-8 encodes the <code>src</code> string to the <code>dest</code> Uint8Array and returns an object 1486containing the read Unicode code units and written UTF-8 bytes.</p> 1487<pre><code class="language-js"><span class="hljs-keyword">const</span> encoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TextEncoder</span>(); 1488<span class="hljs-keyword">const</span> src = <span class="hljs-string">'this is some data'</span>; 1489<span class="hljs-keyword">const</span> dest = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Uint</span>8<span class="hljs-built_in">Array</span>(<span class="hljs-number">10</span>); 1490<span class="hljs-keyword">const</span> { read, written } = encoder.<span class="hljs-title function_">encodeInto</span>(src, dest);</code></pre> 1491<h4><code>textEncoder.encoding</code><span><a class="mark" href="#util_textencoder_encoding" id="util_textencoder_encoding">#</a></span></h4> 1492<ul> 1493<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1494</ul> 1495<p>The encoding supported by the <code>TextEncoder</code> instance. Always set to <code>'utf-8'</code>.</p> 1496</section><section><h3><code>util.toUSVString(string)</code><span><a class="mark" href="#util_util_tousvstring_string" id="util_util_tousvstring_string">#</a></span></h3> 1497<div class="api_metadata"> 1498<span>Added in: v14.18.0</span> 1499</div> 1500<ul> 1501<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1502</ul> 1503<p>Returns the <code>string</code> after replacing any surrogate code points 1504(or equivalently, any unpaired surrogate code units) with the 1505Unicode "replacement character" U+FFFD.</p> 1506</section><section><h3><code>util.types</code><span><a class="mark" href="#util_util_types" id="util_util_types">#</a></span></h3> 1507<div class="api_metadata"> 1508<span>Added in: v10.0.0</span> 1509</div> 1510<p><code>util.types</code> provides type checks for different kinds of built-in objects. 1511Unlike <code>instanceof</code> or <code>Object.prototype.toString.call(value)</code>, these checks do 1512not inspect properties of the object that are accessible from JavaScript (like 1513their prototype), and usually have the overhead of calling into C++.</p> 1514<p>The result generally does not make any guarantees about what kinds of 1515properties or behavior a value exposes in JavaScript. They are primarily 1516useful for addon developers who prefer to do type checking in JavaScript.</p> 1517<h4><code>util.types.isAnyArrayBuffer(value)</code><span><a class="mark" href="#util_util_types_isanyarraybuffer_value" id="util_util_types_isanyarraybuffer_value">#</a></span></h4> 1518<div class="api_metadata"> 1519<span>Added in: v10.0.0</span> 1520</div> 1521<ul> 1522<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1523<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1524</ul> 1525<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or 1526<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> instance.</p> 1527<p>See also <a href="#util_util_types_isarraybuffer_value"><code>util.types.isArrayBuffer()</code></a> and 1528<a href="#util_util_types_issharedarraybuffer_value"><code>util.types.isSharedArrayBuffer()</code></a>.</p> 1529<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isAnyArrayBuffer</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns true</span> 1530util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isAnyArrayBuffer</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">SharedArrayBuffer</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1531<h4><code>util.types.isArrayBufferView(value)</code><span><a class="mark" href="#util_util_types_isarraybufferview_value" id="util_util_types_isarraybufferview_value">#</a></span></h4> 1532<div class="api_metadata"> 1533<span>Added in: v10.0.0</span> 1534</div> 1535<ul> 1536<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1537<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1538</ul> 1539<p>Returns <code>true</code> if the value is an instance of one of the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> 1540views, such as typed array objects or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView"><code>DataView</code></a>. Equivalent to 1541<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/isView"><code>ArrayBuffer.isView()</code></a>.</p> 1542<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isArrayBufferView</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Int</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// true</span> 1543util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isArrayBufferView</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'hello world'</span>)); <span class="hljs-comment">// true</span> 1544util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isArrayBufferView</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">DataView</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>(<span class="hljs-number">16</span>))); <span class="hljs-comment">// true</span> 1545util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isArrayBufferView</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// false</span></code></pre> 1546<h4><code>util.types.isArgumentsObject(value)</code><span><a class="mark" href="#util_util_types_isargumentsobject_value" id="util_util_types_isargumentsobject_value">#</a></span></h4> 1547<div class="api_metadata"> 1548<span>Added in: v10.0.0</span> 1549</div> 1550<ul> 1551<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1552<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1553</ul> 1554<p>Returns <code>true</code> if the value is an <code>arguments</code> object.</p> 1555<!-- eslint-disable prefer-rest-params --> 1556<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) { 1557 util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isArgumentsObject</span>(<span class="hljs-variable language_">arguments</span>); <span class="hljs-comment">// Returns true</span> 1558}</code></pre> 1559<h4><code>util.types.isArrayBuffer(value)</code><span><a class="mark" href="#util_util_types_isarraybuffer_value" id="util_util_types_isarraybuffer_value">#</a></span></h4> 1560<div class="api_metadata"> 1561<span>Added in: v10.0.0</span> 1562</div> 1563<ul> 1564<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1565<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1566</ul> 1567<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> instance. 1568This does <em>not</em> include <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> instances. Usually, it is 1569desirable to test for both; See <a href="#util_util_types_isanyarraybuffer_value"><code>util.types.isAnyArrayBuffer()</code></a> for that.</p> 1570<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isArrayBuffer</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns true</span> 1571util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isArrayBuffer</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">SharedArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1572<h4><code>util.types.isAsyncFunction(value)</code><span><a class="mark" href="#util_util_types_isasyncfunction_value" id="util_util_types_isasyncfunction_value">#</a></span></h4> 1573<div class="api_metadata"> 1574<span>Added in: v10.0.0</span> 1575</div> 1576<ul> 1577<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1578<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1579</ul> 1580<p>Returns <code>true</code> if the value is an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function">async function</a>. 1581This only reports back what the JavaScript engine is seeing; 1582in particular, the return value may not match the original source code if 1583a transpilation tool was used.</p> 1584<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isAsyncFunction</span>(<span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) {}); <span class="hljs-comment">// Returns false</span> 1585util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isAsyncFunction</span>(<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) {}); <span class="hljs-comment">// Returns true</span></code></pre> 1586<h4><code>util.types.isBigInt64Array(value)</code><span><a class="mark" href="#util_util_types_isbigint64array_value" id="util_util_types_isbigint64array_value">#</a></span></h4> 1587<div class="api_metadata"> 1588<span>Added in: v10.0.0</span> 1589</div> 1590<ul> 1591<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1592<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1593</ul> 1594<p>Returns <code>true</code> if the value is a <code>BigInt64Array</code> instance.</p> 1595<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBigInt64Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">BigInt</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1596util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBigInt64Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">BigUint</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1597<h4><code>util.types.isBigUint64Array(value)</code><span><a class="mark" href="#util_util_types_isbiguint64array_value" id="util_util_types_isbiguint64array_value">#</a></span></h4> 1598<div class="api_metadata"> 1599<span>Added in: v10.0.0</span> 1600</div> 1601<ul> 1602<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1603<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1604</ul> 1605<p>Returns <code>true</code> if the value is a <code>BigUint64Array</code> instance.</p> 1606<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBigUint64Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">BigInt</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span> 1607util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBigUint64Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">BigUint</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1608<h4><code>util.types.isBooleanObject(value)</code><span><a class="mark" href="#util_util_types_isbooleanobject_value" id="util_util_types_isbooleanobject_value">#</a></span></h4> 1609<div class="api_metadata"> 1610<span>Added in: v10.0.0</span> 1611</div> 1612<ul> 1613<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1614<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1615</ul> 1616<p>Returns <code>true</code> if the value is a boolean object, e.g. created 1617by <code>new Boolean()</code>.</p> 1618<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBooleanObject</span>(<span class="hljs-literal">false</span>); <span class="hljs-comment">// Returns false</span> 1619util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBooleanObject</span>(<span class="hljs-literal">true</span>); <span class="hljs-comment">// Returns false</span> 1620util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBooleanObject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Boolean</span>(<span class="hljs-literal">false</span>)); <span class="hljs-comment">// Returns true</span> 1621util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBooleanObject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Boolean</span>(<span class="hljs-literal">true</span>)); <span class="hljs-comment">// Returns true</span> 1622util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBooleanObject</span>(<span class="hljs-title class_">Boolean</span>(<span class="hljs-literal">false</span>)); <span class="hljs-comment">// Returns false</span> 1623util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBooleanObject</span>(<span class="hljs-title class_">Boolean</span>(<span class="hljs-literal">true</span>)); <span class="hljs-comment">// Returns false</span></code></pre> 1624<h4><code>util.types.isBoxedPrimitive(value)</code><span><a class="mark" href="#util_util_types_isboxedprimitive_value" id="util_util_types_isboxedprimitive_value">#</a></span></h4> 1625<div class="api_metadata"> 1626<span>Added in: v10.11.0</span> 1627</div> 1628<ul> 1629<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1630<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1631</ul> 1632<p>Returns <code>true</code> if the value is any boxed primitive object, e.g. created 1633by <code>new Boolean()</code>, <code>new String()</code> or <code>Object(Symbol())</code>.</p> 1634<p>For example:</p> 1635<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBoxedPrimitive</span>(<span class="hljs-literal">false</span>); <span class="hljs-comment">// Returns false</span> 1636util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBoxedPrimitive</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Boolean</span>(<span class="hljs-literal">false</span>)); <span class="hljs-comment">// Returns true</span> 1637util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBoxedPrimitive</span>(<span class="hljs-title class_">Symbol</span>(<span class="hljs-string">'foo'</span>)); <span class="hljs-comment">// Returns false</span> 1638util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBoxedPrimitive</span>(<span class="hljs-title class_">Object</span>(<span class="hljs-title class_">Symbol</span>(<span class="hljs-string">'foo'</span>))); <span class="hljs-comment">// Returns true</span> 1639util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isBoxedPrimitive</span>(<span class="hljs-title class_">Object</span>(<span class="hljs-title class_">BigInt</span>(<span class="hljs-number">5</span>))); <span class="hljs-comment">// Returns true</span></code></pre> 1640<h4><code>util.types.isDataView(value)</code><span><a class="mark" href="#util_util_types_isdataview_value" id="util_util_types_isdataview_value">#</a></span></h4> 1641<div class="api_metadata"> 1642<span>Added in: v10.0.0</span> 1643</div> 1644<ul> 1645<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1646<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1647</ul> 1648<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView"><code>DataView</code></a> instance.</p> 1649<pre><code class="language-js"><span class="hljs-keyword">const</span> ab = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>(<span class="hljs-number">20</span>); 1650util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isDataView</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">DataView</span>(ab)); <span class="hljs-comment">// Returns true</span> 1651util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isDataView</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1652<p>See also <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/isView"><code>ArrayBuffer.isView()</code></a>.</p> 1653<h4><code>util.types.isDate(value)</code><span><a class="mark" href="#util_util_types_isdate_value" id="util_util_types_isdate_value">#</a></span></h4> 1654<div class="api_metadata"> 1655<span>Added in: v10.0.0</span> 1656</div> 1657<ul> 1658<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1659<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1660</ul> 1661<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date"><code>Date</code></a> instance.</p> 1662<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isDate</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1663<h4><code>util.types.isExternal(value)</code><span><a class="mark" href="#util_util_types_isexternal_value" id="util_util_types_isexternal_value">#</a></span></h4> 1664<div class="api_metadata"> 1665<span>Added in: v10.0.0</span> 1666</div> 1667<ul> 1668<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1669<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1670</ul> 1671<p>Returns <code>true</code> if the value is a native <code>External</code> value.</p> 1672<p>A native <code>External</code> value is a special type of object that contains a 1673raw C++ pointer (<code>void*</code>) for access from native code, and has no other 1674properties. Such objects are created either by Node.js internals or native 1675addons. In JavaScript, they are <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze">frozen</a> objects with a 1676<code>null</code> prototype.</p> 1677<pre><code class="language-c"><span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><js_native_api.h></span></span> 1678<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><stdlib.h></span></span> 1679napi_value result; 1680<span class="hljs-keyword">static</span> napi_value <span class="hljs-title function_">MyNapi</span><span class="hljs-params">(napi_env env, napi_callback_info info)</span> { 1681 <span class="hljs-type">int</span>* raw = (<span class="hljs-type">int</span>*) <span class="hljs-built_in">malloc</span>(<span class="hljs-number">1024</span>); 1682 napi_status status = napi_create_external(env, (<span class="hljs-type">void</span>*) raw, <span class="hljs-literal">NULL</span>, <span class="hljs-literal">NULL</span>, &result); 1683 <span class="hljs-keyword">if</span> (status != napi_ok) { 1684 napi_throw_error(env, <span class="hljs-literal">NULL</span>, <span class="hljs-string">"napi_create_external failed"</span>); 1685 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1686 } 1687 <span class="hljs-keyword">return</span> result; 1688} 1689... 1690DECLARE_NAPI_PROPERTY(<span class="hljs-string">"myNapi"</span>, MyNapi) 1691...</code></pre> 1692<pre><code class="language-js"><span class="hljs-keyword">const</span> native = <span class="hljs-built_in">require</span>(<span class="hljs-string">'napi_addon.node'</span>); 1693<span class="hljs-keyword">const</span> data = native.<span class="hljs-title function_">myNapi</span>(); 1694util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isExternal</span>(data); <span class="hljs-comment">// returns true</span> 1695util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isExternal</span>(<span class="hljs-number">0</span>); <span class="hljs-comment">// returns false</span> 1696util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isExternal</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">String</span>(<span class="hljs-string">'foo'</span>)); <span class="hljs-comment">// returns false</span></code></pre> 1697<p>For further information on <code>napi_create_external</code>, refer to 1698<a href="n-api.html#n_api_napi_create_external"><code>napi_create_external()</code></a>.</p> 1699<h4><code>util.types.isFloat32Array(value)</code><span><a class="mark" href="#util_util_types_isfloat32array_value" id="util_util_types_isfloat32array_value">#</a></span></h4> 1700<div class="api_metadata"> 1701<span>Added in: v10.0.0</span> 1702</div> 1703<ul> 1704<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1705<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1706</ul> 1707<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float32Array"><code>Float32Array</code></a> instance.</p> 1708<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isFloat32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1709util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isFloat32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>32<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1710util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isFloat32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1711<h4><code>util.types.isFloat64Array(value)</code><span><a class="mark" href="#util_util_types_isfloat64array_value" id="util_util_types_isfloat64array_value">#</a></span></h4> 1712<div class="api_metadata"> 1713<span>Added in: v10.0.0</span> 1714</div> 1715<ul> 1716<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1717<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1718</ul> 1719<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array"><code>Float64Array</code></a> instance.</p> 1720<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isFloat64Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1721util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isFloat64Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Uint</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span> 1722util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isFloat64Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1723<h4><code>util.types.isGeneratorFunction(value)</code><span><a class="mark" href="#util_util_types_isgeneratorfunction_value" id="util_util_types_isgeneratorfunction_value">#</a></span></h4> 1724<div class="api_metadata"> 1725<span>Added in: v10.0.0</span> 1726</div> 1727<ul> 1728<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1729<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1730</ul> 1731<p>Returns <code>true</code> if the value is a generator function. 1732This only reports back what the JavaScript engine is seeing; 1733in particular, the return value may not match the original source code if 1734a transpilation tool was used.</p> 1735<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isGeneratorFunction</span>(<span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) {}); <span class="hljs-comment">// Returns false</span> 1736util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isGeneratorFunction</span>(<span class="hljs-keyword">function</span>* <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) {}); <span class="hljs-comment">// Returns true</span></code></pre> 1737<h4><code>util.types.isGeneratorObject(value)</code><span><a class="mark" href="#util_util_types_isgeneratorobject_value" id="util_util_types_isgeneratorobject_value">#</a></span></h4> 1738<div class="api_metadata"> 1739<span>Added in: v10.0.0</span> 1740</div> 1741<ul> 1742<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1743<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1744</ul> 1745<p>Returns <code>true</code> if the value is a generator object as returned from a 1746built-in generator function. 1747This only reports back what the JavaScript engine is seeing; 1748in particular, the return value may not match the original source code if 1749a transpilation tool was used.</p> 1750<pre><code class="language-js"><span class="hljs-keyword">function</span>* <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) {} 1751<span class="hljs-keyword">const</span> generator = <span class="hljs-title function_">foo</span>(); 1752util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isGeneratorObject</span>(generator); <span class="hljs-comment">// Returns true</span></code></pre> 1753<h4><code>util.types.isInt8Array(value)</code><span><a class="mark" href="#util_util_types_isint8array_value" id="util_util_types_isint8array_value">#</a></span></h4> 1754<div class="api_metadata"> 1755<span>Added in: v10.0.0</span> 1756</div> 1757<ul> 1758<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1759<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1760</ul> 1761<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int8Array"><code>Int8Array</code></a> instance.</p> 1762<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt8Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1763util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt8Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Int</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1764util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt8Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1765<h4><code>util.types.isInt16Array(value)</code><span><a class="mark" href="#util_util_types_isint16array_value" id="util_util_types_isint16array_value">#</a></span></h4> 1766<div class="api_metadata"> 1767<span>Added in: v10.0.0</span> 1768</div> 1769<ul> 1770<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1771<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1772</ul> 1773<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int16Array"><code>Int16Array</code></a> instance.</p> 1774<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt16Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1775util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt16Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Int</span>16<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1776util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt16Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1777<h4><code>util.types.isInt32Array(value)</code><span><a class="mark" href="#util_util_types_isint32array_value" id="util_util_types_isint32array_value">#</a></span></h4> 1778<div class="api_metadata"> 1779<span>Added in: v10.0.0</span> 1780</div> 1781<ul> 1782<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1783<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1784</ul> 1785<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Int32Array"><code>Int32Array</code></a> instance.</p> 1786<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1787util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Int</span>32<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1788util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isInt32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1789<h4><code>util.types.isMap(value)</code><span><a class="mark" href="#util_util_types_ismap_value" id="util_util_types_ismap_value">#</a></span></h4> 1790<div class="api_metadata"> 1791<span>Added in: v10.0.0</span> 1792</div> 1793<ul> 1794<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1795<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1796</ul> 1797<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map"><code>Map</code></a> instance.</p> 1798<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isMap</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Map</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1799<h4><code>util.types.isMapIterator(value)</code><span><a class="mark" href="#util_util_types_ismapiterator_value" id="util_util_types_ismapiterator_value">#</a></span></h4> 1800<div class="api_metadata"> 1801<span>Added in: v10.0.0</span> 1802</div> 1803<ul> 1804<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1805<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1806</ul> 1807<p>Returns <code>true</code> if the value is an iterator returned for a built-in 1808<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map"><code>Map</code></a> instance.</p> 1809<pre><code class="language-js"><span class="hljs-keyword">const</span> map = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Map</span>(); 1810util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isMapIterator</span>(map.<span class="hljs-title function_">keys</span>()); <span class="hljs-comment">// Returns true</span> 1811util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isMapIterator</span>(map.<span class="hljs-title function_">values</span>()); <span class="hljs-comment">// Returns true</span> 1812util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isMapIterator</span>(map.<span class="hljs-title function_">entries</span>()); <span class="hljs-comment">// Returns true</span> 1813util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isMapIterator</span>(map[<span class="hljs-title class_">Symbol</span>.<span class="hljs-property">iterator</span>]()); <span class="hljs-comment">// Returns true</span></code></pre> 1814<h4><code>util.types.isModuleNamespaceObject(value)</code><span><a class="mark" href="#util_util_types_ismodulenamespaceobject_value" id="util_util_types_ismodulenamespaceobject_value">#</a></span></h4> 1815<div class="api_metadata"> 1816<span>Added in: v10.0.0</span> 1817</div> 1818<ul> 1819<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1820<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1821</ul> 1822<p>Returns <code>true</code> if the value is an instance of a <a href="https://tc39.github.io/ecma262/#sec-module-namespace-exotic-objects">Module Namespace Object</a>.</p> 1823<!-- eslint-skip --> 1824<pre><code class="language-js"><span class="hljs-keyword">import</span> * <span class="hljs-keyword">as</span> ns <span class="hljs-keyword">from</span> <span class="hljs-string">'./a.js'</span>; 1825 1826util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isModuleNamespaceObject</span>(ns); <span class="hljs-comment">// Returns true</span></code></pre> 1827<h4><code>util.types.isNativeError(value)</code><span><a class="mark" href="#util_util_types_isnativeerror_value" id="util_util_types_isnativeerror_value">#</a></span></h4> 1828<div class="api_metadata"> 1829<span>Added in: v10.0.0</span> 1830</div> 1831<ul> 1832<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1833<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1834</ul> 1835<p>Returns <code>true</code> if the value is an instance of a built-in <a href="errors.html#errors_class_error"><code>Error</code></a> type.</p> 1836<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isNativeError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>()); <span class="hljs-comment">// Returns true</span> 1837util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isNativeError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>()); <span class="hljs-comment">// Returns true</span> 1838util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isNativeError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">RangeError</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1839<h4><code>util.types.isNumberObject(value)</code><span><a class="mark" href="#util_util_types_isnumberobject_value" id="util_util_types_isnumberobject_value">#</a></span></h4> 1840<div class="api_metadata"> 1841<span>Added in: v10.0.0</span> 1842</div> 1843<ul> 1844<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1845<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1846</ul> 1847<p>Returns <code>true</code> if the value is a number object, e.g. created 1848by <code>new Number()</code>.</p> 1849<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isNumberObject</span>(<span class="hljs-number">0</span>); <span class="hljs-comment">// Returns false</span> 1850util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isNumberObject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Number</span>(<span class="hljs-number">0</span>)); <span class="hljs-comment">// Returns true</span></code></pre> 1851<h4><code>util.types.isPromise(value)</code><span><a class="mark" href="#util_util_types_ispromise_value" id="util_util_types_ispromise_value">#</a></span></h4> 1852<div class="api_metadata"> 1853<span>Added in: v10.0.0</span> 1854</div> 1855<ul> 1856<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1857<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1858</ul> 1859<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise"><code>Promise</code></a>.</p> 1860<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isPromise</span>(<span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">resolve</span>(<span class="hljs-number">42</span>)); <span class="hljs-comment">// Returns true</span></code></pre> 1861<h4><code>util.types.isProxy(value)</code><span><a class="mark" href="#util_util_types_isproxy_value" id="util_util_types_isproxy_value">#</a></span></h4> 1862<div class="api_metadata"> 1863<span>Added in: v10.0.0</span> 1864</div> 1865<ul> 1866<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1867<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1868</ul> 1869<p>Returns <code>true</code> if the value is a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy"><code>Proxy</code></a> instance.</p> 1870<pre><code class="language-js"><span class="hljs-keyword">const</span> target = {}; 1871<span class="hljs-keyword">const</span> proxy = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Proxy</span>(target, {}); 1872util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isProxy</span>(target); <span class="hljs-comment">// Returns false</span> 1873util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isProxy</span>(proxy); <span class="hljs-comment">// Returns true</span></code></pre> 1874<h4><code>util.types.isRegExp(value)</code><span><a class="mark" href="#util_util_types_isregexp_value" id="util_util_types_isregexp_value">#</a></span></h4> 1875<div class="api_metadata"> 1876<span>Added in: v10.0.0</span> 1877</div> 1878<ul> 1879<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1880<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1881</ul> 1882<p>Returns <code>true</code> if the value is a regular expression object.</p> 1883<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isRegExp</span>(<span class="hljs-regexp">/abc/</span>); <span class="hljs-comment">// Returns true</span> 1884util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isRegExp</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">RegExp</span>(<span class="hljs-string">'abc'</span>)); <span class="hljs-comment">// Returns true</span></code></pre> 1885<h4><code>util.types.isSet(value)</code><span><a class="mark" href="#util_util_types_isset_value" id="util_util_types_isset_value">#</a></span></h4> 1886<div class="api_metadata"> 1887<span>Added in: v10.0.0</span> 1888</div> 1889<ul> 1890<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1891<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1892</ul> 1893<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set"><code>Set</code></a> instance.</p> 1894<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSet</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Set</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1895<h4><code>util.types.isSetIterator(value)</code><span><a class="mark" href="#util_util_types_issetiterator_value" id="util_util_types_issetiterator_value">#</a></span></h4> 1896<div class="api_metadata"> 1897<span>Added in: v10.0.0</span> 1898</div> 1899<ul> 1900<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1901<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1902</ul> 1903<p>Returns <code>true</code> if the value is an iterator returned for a built-in 1904<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set"><code>Set</code></a> instance.</p> 1905<pre><code class="language-js"><span class="hljs-keyword">const</span> set = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Set</span>(); 1906util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSetIterator</span>(set.<span class="hljs-title function_">keys</span>()); <span class="hljs-comment">// Returns true</span> 1907util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSetIterator</span>(set.<span class="hljs-title function_">values</span>()); <span class="hljs-comment">// Returns true</span> 1908util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSetIterator</span>(set.<span class="hljs-title function_">entries</span>()); <span class="hljs-comment">// Returns true</span> 1909util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSetIterator</span>(set[<span class="hljs-title class_">Symbol</span>.<span class="hljs-property">iterator</span>]()); <span class="hljs-comment">// Returns true</span></code></pre> 1910<h4><code>util.types.isSharedArrayBuffer(value)</code><span><a class="mark" href="#util_util_types_issharedarraybuffer_value" id="util_util_types_issharedarraybuffer_value">#</a></span></h4> 1911<div class="api_metadata"> 1912<span>Added in: v10.0.0</span> 1913</div> 1914<ul> 1915<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1916<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1917</ul> 1918<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> instance. 1919This does <em>not</em> include <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> instances. Usually, it is 1920desirable to test for both; See <a href="#util_util_types_isanyarraybuffer_value"><code>util.types.isAnyArrayBuffer()</code></a> for that.</p> 1921<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSharedArrayBuffer</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1922util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSharedArrayBuffer</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">SharedArrayBuffer</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1923<h4><code>util.types.isStringObject(value)</code><span><a class="mark" href="#util_util_types_isstringobject_value" id="util_util_types_isstringobject_value">#</a></span></h4> 1924<div class="api_metadata"> 1925<span>Added in: v10.0.0</span> 1926</div> 1927<ul> 1928<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1929<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1930</ul> 1931<p>Returns <code>true</code> if the value is a string object, e.g. created 1932by <code>new String()</code>.</p> 1933<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isStringObject</span>(<span class="hljs-string">'foo'</span>); <span class="hljs-comment">// Returns false</span> 1934util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isStringObject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">String</span>(<span class="hljs-string">'foo'</span>)); <span class="hljs-comment">// Returns true</span></code></pre> 1935<h4><code>util.types.isSymbolObject(value)</code><span><a class="mark" href="#util_util_types_issymbolobject_value" id="util_util_types_issymbolobject_value">#</a></span></h4> 1936<div class="api_metadata"> 1937<span>Added in: v10.0.0</span> 1938</div> 1939<ul> 1940<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1941<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1942</ul> 1943<p>Returns <code>true</code> if the value is a symbol object, created 1944by calling <code>Object()</code> on a <code>Symbol</code> primitive.</p> 1945<pre><code class="language-js"><span class="hljs-keyword">const</span> symbol = <span class="hljs-title class_">Symbol</span>(<span class="hljs-string">'foo'</span>); 1946util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSymbolObject</span>(symbol); <span class="hljs-comment">// Returns false</span> 1947util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSymbolObject</span>(<span class="hljs-title class_">Object</span>(symbol)); <span class="hljs-comment">// Returns true</span></code></pre> 1948<h4><code>util.types.isTypedArray(value)</code><span><a class="mark" href="#util_util_types_istypedarray_value" id="util_util_types_istypedarray_value">#</a></span></h4> 1949<div class="api_metadata"> 1950<span>Added in: v10.0.0</span> 1951</div> 1952<ul> 1953<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1954<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1955</ul> 1956<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance.</p> 1957<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isTypedArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1958util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isTypedArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Uint</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1959util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isTypedArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 1960<p>See also <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/isView"><code>ArrayBuffer.isView()</code></a>.</p> 1961<h4><code>util.types.isUint8Array(value)</code><span><a class="mark" href="#util_util_types_isuint8array_value" id="util_util_types_isuint8array_value">#</a></span></h4> 1962<div class="api_metadata"> 1963<span>Added in: v10.0.0</span> 1964</div> 1965<ul> 1966<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1967<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1968</ul> 1969<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> instance.</p> 1970<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint8Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1971util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint8Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Uint</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1972util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint8Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1973<h4><code>util.types.isUint8ClampedArray(value)</code><span><a class="mark" href="#util_util_types_isuint8clampedarray_value" id="util_util_types_isuint8clampedarray_value">#</a></span></h4> 1974<div class="api_metadata"> 1975<span>Added in: v10.0.0</span> 1976</div> 1977<ul> 1978<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1979<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1980</ul> 1981<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8ClampedArray"><code>Uint8ClampedArray</code></a> instance.</p> 1982<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint8ClampedArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1983util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint8ClampedArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Uint</span>8ClampedArray()); <span class="hljs-comment">// Returns true</span> 1984util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint8ClampedArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1985<h4><code>util.types.isUint16Array(value)</code><span><a class="mark" href="#util_util_types_isuint16array_value" id="util_util_types_isuint16array_value">#</a></span></h4> 1986<div class="api_metadata"> 1987<span>Added in: v10.0.0</span> 1988</div> 1989<ul> 1990<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1991<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1992</ul> 1993<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint16Array"><code>Uint16Array</code></a> instance.</p> 1994<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint16Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 1995util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint16Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Uint</span>16<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1996util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint16Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 1997<h4><code>util.types.isUint32Array(value)</code><span><a class="mark" href="#util_util_types_isuint32array_value" id="util_util_types_isuint32array_value">#</a></span></h4> 1998<div class="api_metadata"> 1999<span>Added in: v10.0.0</span> 2000</div> 2001<ul> 2002<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2003<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2004</ul> 2005<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array"><code>Uint32Array</code></a> instance.</p> 2006<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayBuffer</span>()); <span class="hljs-comment">// Returns false</span> 2007util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Uint</span>32<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 2008util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isUint32Array</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Float</span>64<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span></code></pre> 2009<h4><code>util.types.isWeakMap(value)</code><span><a class="mark" href="#util_util_types_isweakmap_value" id="util_util_types_isweakmap_value">#</a></span></h4> 2010<div class="api_metadata"> 2011<span>Added in: v10.0.0</span> 2012</div> 2013<ul> 2014<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2015<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2016</ul> 2017<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap"><code>WeakMap</code></a> instance.</p> 2018<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isWeakMap</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakMap</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 2019<h4><code>util.types.isWeakSet(value)</code><span><a class="mark" href="#util_util_types_isweakset_value" id="util_util_types_isweakset_value">#</a></span></h4> 2020<div class="api_metadata"> 2021<span>Added in: v10.0.0</span> 2022</div> 2023<ul> 2024<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2025<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2026</ul> 2027<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet"><code>WeakSet</code></a> instance.</p> 2028<pre><code class="language-js">util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isWeakSet</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakSet</span>()); <span class="hljs-comment">// Returns true</span></code></pre> 2029<h4><code>util.types.isWebAssemblyCompiledModule(value)</code><span><a class="mark" href="#util_util_types_iswebassemblycompiledmodule_value" id="util_util_types_iswebassemblycompiledmodule_value">#</a></span></h4> 2030<div class="api_metadata"> 2031<span>Added in: v10.0.0</span><span>Deprecated since: v14.0.0</span> 2032</div> 2033<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>value instanceof WebAssembly.Module</code> instead.</div><p></p> 2034<ul> 2035<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2036<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2037</ul> 2038<p>Returns <code>true</code> if the value is a built-in <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Module"><code>WebAssembly.Module</code></a> instance.</p> 2039<pre><code class="language-js"><span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WebAssembly</span>.<span class="hljs-title class_">Module</span>(wasmBuffer); 2040util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isWebAssemblyCompiledModule</span>(<span class="hljs-variable language_">module</span>); <span class="hljs-comment">// Returns true</span></code></pre> 2041</section><section><h3>Deprecated APIs<span><a class="mark" href="#util_deprecated_apis" id="util_deprecated_apis">#</a></span></h3> 2042<p>The following APIs are deprecated and should no longer be used. Existing 2043applications and modules should be updated to find alternative approaches.</p> 2044<h4><code>util._extend(target, source)</code><span><a class="mark" href="#util_util_extend_target_source" id="util_util_extend_target_source">#</a></span></h4> 2045<div class="api_metadata"> 2046<span>Added in: v0.7.5</span><span>Deprecated since: v6.0.0</span> 2047</div> 2048<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign"><code>Object.assign()</code></a> instead.</div><p></p> 2049<ul> 2050<li><code>target</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2051<li><code>source</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2052</ul> 2053<p>The <code>util._extend()</code> method was never intended to be used outside of internal 2054Node.js modules. The community found and used it anyway.</p> 2055<p>It is deprecated and should not be used in new code. JavaScript comes with very 2056similar built-in functionality through <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign"><code>Object.assign()</code></a>.</p> 2057<h4><code>util.isArray(object)</code><span><a class="mark" href="#util_util_isarray_object" id="util_util_isarray_object">#</a></span></h4> 2058<div class="api_metadata"> 2059<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2060</div> 2061<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray"><code>Array.isArray()</code></a> instead.</div><p></p> 2062<ul> 2063<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2064<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2065</ul> 2066<p>Alias for <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray"><code>Array.isArray()</code></a>.</p> 2067<p>Returns <code>true</code> if the given <code>object</code> is an <code>Array</code>. Otherwise, returns <code>false</code>.</p> 2068<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2069 2070util.<span class="hljs-title function_">isArray</span>([]); 2071<span class="hljs-comment">// Returns: true</span> 2072util.<span class="hljs-title function_">isArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Array</span>()); 2073<span class="hljs-comment">// Returns: true</span> 2074util.<span class="hljs-title function_">isArray</span>({}); 2075<span class="hljs-comment">// Returns: false</span></code></pre> 2076<h4><code>util.isBoolean(object)</code><span><a class="mark" href="#util_util_isboolean_object" id="util_util_isboolean_object">#</a></span></h4> 2077<div class="api_metadata"> 2078<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2079</div> 2080<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>typeof value === 'boolean'</code> instead.</div><p></p> 2081<ul> 2082<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2083<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2084</ul> 2085<p>Returns <code>true</code> if the given <code>object</code> is a <code>Boolean</code>. Otherwise, returns <code>false</code>.</p> 2086<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2087 2088util.<span class="hljs-title function_">isBoolean</span>(<span class="hljs-number">1</span>); 2089<span class="hljs-comment">// Returns: false</span> 2090util.<span class="hljs-title function_">isBoolean</span>(<span class="hljs-number">0</span>); 2091<span class="hljs-comment">// Returns: false</span> 2092util.<span class="hljs-title function_">isBoolean</span>(<span class="hljs-literal">false</span>); 2093<span class="hljs-comment">// Returns: true</span></code></pre> 2094<h4><code>util.isBuffer(object)</code><span><a class="mark" href="#util_util_isbuffer_object" id="util_util_isbuffer_object">#</a></span></h4> 2095<div class="api_metadata"> 2096<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2097</div> 2098<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="buffer.html#buffer_static_method_buffer_isbuffer_obj"><code>Buffer.isBuffer()</code></a> instead.</div><p></p> 2099<ul> 2100<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2101<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2102</ul> 2103<p>Returns <code>true</code> if the given <code>object</code> is a <code>Buffer</code>. Otherwise, returns <code>false</code>.</p> 2104<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2105 2106util.<span class="hljs-title function_">isBuffer</span>({ <span class="hljs-attr">length</span>: <span class="hljs-number">0</span> }); 2107<span class="hljs-comment">// Returns: false</span> 2108util.<span class="hljs-title function_">isBuffer</span>([]); 2109<span class="hljs-comment">// Returns: false</span> 2110util.<span class="hljs-title function_">isBuffer</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'hello world'</span>)); 2111<span class="hljs-comment">// Returns: true</span></code></pre> 2112<h4><code>util.isDate(object)</code><span><a class="mark" href="#util_util_isdate_object" id="util_util_isdate_object">#</a></span></h4> 2113<div class="api_metadata"> 2114<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2115</div> 2116<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#util_util_types_isdate_value"><code>util.types.isDate()</code></a> instead.</div><p></p> 2117<ul> 2118<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2119<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2120</ul> 2121<p>Returns <code>true</code> if the given <code>object</code> is a <code>Date</code>. Otherwise, returns <code>false</code>.</p> 2122<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2123 2124util.<span class="hljs-title function_">isDate</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>()); 2125<span class="hljs-comment">// Returns: true</span> 2126util.<span class="hljs-title function_">isDate</span>(<span class="hljs-title class_">Date</span>()); 2127<span class="hljs-comment">// false (without 'new' returns a String)</span> 2128util.<span class="hljs-title function_">isDate</span>({}); 2129<span class="hljs-comment">// Returns: false</span></code></pre> 2130<h4><code>util.isError(object)</code><span><a class="mark" href="#util_util_iserror_object" id="util_util_iserror_object">#</a></span></h4> 2131<div class="api_metadata"> 2132<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2133</div> 2134<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <a href="#util_util_types_isnativeerror_value"><code>util.types.isNativeError()</code></a> instead.</div><p></p> 2135<ul> 2136<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2137<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2138</ul> 2139<p>Returns <code>true</code> if the given <code>object</code> is an <a href="errors.html#errors_class_error"><code>Error</code></a>. Otherwise, returns 2140<code>false</code>.</p> 2141<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2142 2143util.<span class="hljs-title function_">isError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>()); 2144<span class="hljs-comment">// Returns: true</span> 2145util.<span class="hljs-title function_">isError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>()); 2146<span class="hljs-comment">// Returns: true</span> 2147util.<span class="hljs-title function_">isError</span>({ <span class="hljs-attr">name</span>: <span class="hljs-string">'Error'</span>, <span class="hljs-attr">message</span>: <span class="hljs-string">'an error occurred'</span> }); 2148<span class="hljs-comment">// Returns: false</span></code></pre> 2149<p>This method relies on <code>Object.prototype.toString()</code> behavior. It is 2150possible to obtain an incorrect result when the <code>object</code> argument manipulates 2151<code>@@toStringTag</code>.</p> 2152<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2153<span class="hljs-keyword">const</span> obj = { <span class="hljs-attr">name</span>: <span class="hljs-string">'Error'</span>, <span class="hljs-attr">message</span>: <span class="hljs-string">'an error occurred'</span> }; 2154 2155util.<span class="hljs-title function_">isError</span>(obj); 2156<span class="hljs-comment">// Returns: false</span> 2157obj[<span class="hljs-title class_">Symbol</span>.<span class="hljs-property">toStringTag</span>] = <span class="hljs-string">'Error'</span>; 2158util.<span class="hljs-title function_">isError</span>(obj); 2159<span class="hljs-comment">// Returns: true</span></code></pre> 2160<h4><code>util.isFunction(object)</code><span><a class="mark" href="#util_util_isfunction_object" id="util_util_isfunction_object">#</a></span></h4> 2161<div class="api_metadata"> 2162<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2163</div> 2164<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>typeof value === 'function'</code> instead.</div><p></p> 2165<ul> 2166<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2167<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2168</ul> 2169<p>Returns <code>true</code> if the given <code>object</code> is a <code>Function</code>. Otherwise, returns 2170<code>false</code>.</p> 2171<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2172 2173<span class="hljs-keyword">function</span> <span class="hljs-title function_">Foo</span>(<span class="hljs-params"></span>) {} 2174<span class="hljs-keyword">const</span> <span class="hljs-title function_">Bar</span> = (<span class="hljs-params"></span>) => {}; 2175 2176util.<span class="hljs-title function_">isFunction</span>({}); 2177<span class="hljs-comment">// Returns: false</span> 2178util.<span class="hljs-title function_">isFunction</span>(<span class="hljs-title class_">Foo</span>); 2179<span class="hljs-comment">// Returns: true</span> 2180util.<span class="hljs-title function_">isFunction</span>(<span class="hljs-title class_">Bar</span>); 2181<span class="hljs-comment">// Returns: true</span></code></pre> 2182<h4><code>util.isNull(object)</code><span><a class="mark" href="#util_util_isnull_object" id="util_util_isnull_object">#</a></span></h4> 2183<div class="api_metadata"> 2184<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2185</div> 2186<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>value === null</code> instead.</div><p></p> 2187<ul> 2188<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2189<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2190</ul> 2191<p>Returns <code>true</code> if the given <code>object</code> is strictly <code>null</code>. Otherwise, returns 2192<code>false</code>.</p> 2193<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2194 2195util.<span class="hljs-title function_">isNull</span>(<span class="hljs-number">0</span>); 2196<span class="hljs-comment">// Returns: false</span> 2197util.<span class="hljs-title function_">isNull</span>(<span class="hljs-literal">undefined</span>); 2198<span class="hljs-comment">// Returns: false</span> 2199util.<span class="hljs-title function_">isNull</span>(<span class="hljs-literal">null</span>); 2200<span class="hljs-comment">// Returns: true</span></code></pre> 2201<h4><code>util.isNullOrUndefined(object)</code><span><a class="mark" href="#util_util_isnullorundefined_object" id="util_util_isnullorundefined_object">#</a></span></h4> 2202<div class="api_metadata"> 2203<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2204</div> 2205<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use 2206<code>value === undefined || value === null</code> instead.</div><p></p> 2207<ul> 2208<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2209<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2210</ul> 2211<p>Returns <code>true</code> if the given <code>object</code> is <code>null</code> or <code>undefined</code>. Otherwise, 2212returns <code>false</code>.</p> 2213<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2214 2215util.<span class="hljs-title function_">isNullOrUndefined</span>(<span class="hljs-number">0</span>); 2216<span class="hljs-comment">// Returns: false</span> 2217util.<span class="hljs-title function_">isNullOrUndefined</span>(<span class="hljs-literal">undefined</span>); 2218<span class="hljs-comment">// Returns: true</span> 2219util.<span class="hljs-title function_">isNullOrUndefined</span>(<span class="hljs-literal">null</span>); 2220<span class="hljs-comment">// Returns: true</span></code></pre> 2221<h4><code>util.isNumber(object)</code><span><a class="mark" href="#util_util_isnumber_object" id="util_util_isnumber_object">#</a></span></h4> 2222<div class="api_metadata"> 2223<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2224</div> 2225<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>typeof value === 'number'</code> instead.</div><p></p> 2226<ul> 2227<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2228<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2229</ul> 2230<p>Returns <code>true</code> if the given <code>object</code> is a <code>Number</code>. Otherwise, returns <code>false</code>.</p> 2231<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2232 2233util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-literal">false</span>); 2234<span class="hljs-comment">// Returns: false</span> 2235util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-title class_">Infinity</span>); 2236<span class="hljs-comment">// Returns: true</span> 2237util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-number">0</span>); 2238<span class="hljs-comment">// Returns: true</span> 2239util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-title class_">Na</span>N); 2240<span class="hljs-comment">// Returns: true</span></code></pre> 2241<h4><code>util.isObject(object)</code><span><a class="mark" href="#util_util_isobject_object" id="util_util_isobject_object">#</a></span></h4> 2242<div class="api_metadata"> 2243<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2244</div> 2245<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: 2246Use <code>value !== null && typeof value === 'object'</code> instead.</div><p></p> 2247<ul> 2248<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2249<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2250</ul> 2251<p>Returns <code>true</code> if the given <code>object</code> is strictly an <code>Object</code> <strong>and</strong> not a 2252<code>Function</code> (even though functions are objects in JavaScript). 2253Otherwise, returns <code>false</code>.</p> 2254<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2255 2256util.<span class="hljs-title function_">isObject</span>(<span class="hljs-number">5</span>); 2257<span class="hljs-comment">// Returns: false</span> 2258util.<span class="hljs-title function_">isObject</span>(<span class="hljs-literal">null</span>); 2259<span class="hljs-comment">// Returns: false</span> 2260util.<span class="hljs-title function_">isObject</span>({}); 2261<span class="hljs-comment">// Returns: true</span> 2262util.<span class="hljs-title function_">isObject</span>(<span class="hljs-function">() =></span> {}); 2263<span class="hljs-comment">// Returns: false</span></code></pre> 2264<h4><code>util.isPrimitive(object)</code><span><a class="mark" href="#util_util_isprimitive_object" id="util_util_isprimitive_object">#</a></span></h4> 2265<div class="api_metadata"> 2266<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2267</div> 2268<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use 2269<code>(typeof value !== 'object' && typeof value !== 'function') || value === null</code> 2270instead.</div><p></p> 2271<ul> 2272<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2273<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2274</ul> 2275<p>Returns <code>true</code> if the given <code>object</code> is a primitive type. Otherwise, returns 2276<code>false</code>.</p> 2277<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2278 2279util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-number">5</span>); 2280<span class="hljs-comment">// Returns: true</span> 2281util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-string">'foo'</span>); 2282<span class="hljs-comment">// Returns: true</span> 2283util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-literal">false</span>); 2284<span class="hljs-comment">// Returns: true</span> 2285util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-literal">null</span>); 2286<span class="hljs-comment">// Returns: true</span> 2287util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-literal">undefined</span>); 2288<span class="hljs-comment">// Returns: true</span> 2289util.<span class="hljs-title function_">isPrimitive</span>({}); 2290<span class="hljs-comment">// Returns: false</span> 2291util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-function">() =></span> {}); 2292<span class="hljs-comment">// Returns: false</span> 2293util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-regexp">/^$/</span>); 2294<span class="hljs-comment">// Returns: false</span> 2295util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>()); 2296<span class="hljs-comment">// Returns: false</span></code></pre> 2297<h4><code>util.isRegExp(object)</code><span><a class="mark" href="#util_util_isregexp_object" id="util_util_isregexp_object">#</a></span></h4> 2298<div class="api_metadata"> 2299<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2300</div> 2301<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated</div><p></p> 2302<ul> 2303<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2304<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2305</ul> 2306<p>Returns <code>true</code> if the given <code>object</code> is a <code>RegExp</code>. Otherwise, returns <code>false</code>.</p> 2307<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2308 2309util.<span class="hljs-title function_">isRegExp</span>(<span class="hljs-regexp">/some regexp/</span>); 2310<span class="hljs-comment">// Returns: true</span> 2311util.<span class="hljs-title function_">isRegExp</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">RegExp</span>(<span class="hljs-string">'another regexp'</span>)); 2312<span class="hljs-comment">// Returns: true</span> 2313util.<span class="hljs-title function_">isRegExp</span>({}); 2314<span class="hljs-comment">// Returns: false</span></code></pre> 2315<h4><code>util.isString(object)</code><span><a class="mark" href="#util_util_isstring_object" id="util_util_isstring_object">#</a></span></h4> 2316<div class="api_metadata"> 2317<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2318</div> 2319<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>typeof value === 'string'</code> instead.</div><p></p> 2320<ul> 2321<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2322<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2323</ul> 2324<p>Returns <code>true</code> if the given <code>object</code> is a <code>string</code>. Otherwise, returns <code>false</code>.</p> 2325<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2326 2327util.<span class="hljs-title function_">isString</span>(<span class="hljs-string">''</span>); 2328<span class="hljs-comment">// Returns: true</span> 2329util.<span class="hljs-title function_">isString</span>(<span class="hljs-string">'foo'</span>); 2330<span class="hljs-comment">// Returns: true</span> 2331util.<span class="hljs-title function_">isString</span>(<span class="hljs-title class_">String</span>(<span class="hljs-string">'foo'</span>)); 2332<span class="hljs-comment">// Returns: true</span> 2333util.<span class="hljs-title function_">isString</span>(<span class="hljs-number">5</span>); 2334<span class="hljs-comment">// Returns: false</span></code></pre> 2335<h4><code>util.isSymbol(object)</code><span><a class="mark" href="#util_util_issymbol_object" id="util_util_issymbol_object">#</a></span></h4> 2336<div class="api_metadata"> 2337<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2338</div> 2339<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>typeof value === 'symbol'</code> instead.</div><p></p> 2340<ul> 2341<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2342<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2343</ul> 2344<p>Returns <code>true</code> if the given <code>object</code> is a <code>Symbol</code>. Otherwise, returns <code>false</code>.</p> 2345<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2346 2347util.<span class="hljs-title function_">isSymbol</span>(<span class="hljs-number">5</span>); 2348<span class="hljs-comment">// Returns: false</span> 2349util.<span class="hljs-title function_">isSymbol</span>(<span class="hljs-string">'foo'</span>); 2350<span class="hljs-comment">// Returns: false</span> 2351util.<span class="hljs-title function_">isSymbol</span>(<span class="hljs-title class_">Symbol</span>(<span class="hljs-string">'foo'</span>)); 2352<span class="hljs-comment">// Returns: true</span></code></pre> 2353<h4><code>util.isUndefined(object)</code><span><a class="mark" href="#util_util_isundefined_object" id="util_util_isundefined_object">#</a></span></h4> 2354<div class="api_metadata"> 2355<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2356</div> 2357<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use <code>value === undefined</code> instead.</div><p></p> 2358<ul> 2359<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2360<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2361</ul> 2362<p>Returns <code>true</code> if the given <code>object</code> is <code>undefined</code>. Otherwise, returns <code>false</code>.</p> 2363<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2364 2365<span class="hljs-keyword">const</span> foo = <span class="hljs-literal">undefined</span>; 2366util.<span class="hljs-title function_">isUndefined</span>(<span class="hljs-number">5</span>); 2367<span class="hljs-comment">// Returns: false</span> 2368util.<span class="hljs-title function_">isUndefined</span>(foo); 2369<span class="hljs-comment">// Returns: true</span> 2370util.<span class="hljs-title function_">isUndefined</span>(<span class="hljs-literal">null</span>); 2371<span class="hljs-comment">// Returns: false</span></code></pre> 2372<h4><code>util.log(string)</code><span><a class="mark" href="#util_util_log_string" id="util_util_log_string">#</a></span></h4> 2373<div class="api_metadata"> 2374<span>Added in: v0.3.0</span><span>Deprecated since: v6.0.0</span> 2375</div> 2376<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use a third party module instead.</div><p></p> 2377<ul> 2378<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2379</ul> 2380<p>The <code>util.log()</code> method prints the given <code>string</code> to <code>stdout</code> with an included 2381timestamp.</p> 2382<pre><code class="language-js"><span class="hljs-keyword">const</span> util = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); 2383 2384util.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Timestamped message.'</span>);</code></pre></section> 2385 <!-- API END --> 2386 </div> 2387 </div> 2388 </div> 2389 <script> 2390 'use strict'; 2391 { 2392 const kCustomPreference = 'customDarkTheme'; 2393 const userSettings = sessionStorage.getItem(kCustomPreference); 2394 const themeToggleButton = document.getElementById('theme-toggle-btn'); 2395 if (userSettings === null && window.matchMedia) { 2396 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 2397 if ('onchange' in mq) { 2398 function mqChangeListener(e) { 2399 document.body.classList.toggle('dark-mode', e.matches); 2400 } 2401 mq.addEventListener('change', mqChangeListener); 2402 if (themeToggleButton) { 2403 themeToggleButton.addEventListener('click', function() { 2404 mq.removeEventListener('change', mqChangeListener); 2405 }, { once: true }); 2406 } 2407 } 2408 if (mq.matches) { 2409 document.body.classList.add('dark-mode'); 2410 } 2411 } else if (userSettings === 'true') { 2412 document.body.classList.add('dark-mode'); 2413 } 2414 if (themeToggleButton) { 2415 themeToggleButton.hidden = false; 2416 themeToggleButton.addEventListener('click', function() { 2417 sessionStorage.setItem( 2418 kCustomPreference, 2419 document.body.classList.toggle('dark-mode') 2420 ); 2421 }); 2422 } 2423 } 2424 </script> 2425</body> 2426</html> 2427