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<header> 91 <div class="header-container"> 92 <h1>Node.js v14.21.2 documentation</h1> 93 <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 94 <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 95 <path fill="none" d="M0 0h24v24H0z" /> 96 <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 97 <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 98 </svg> 99 <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 100 <path d="M0 0h24v24H0z" fill="none" /> 101 <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 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href="https://nodejs.org/docs/latest-v0.12.x/api/util.html">0.12.x</a></li> 136<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/util.html">0.10.x</a></li></ol> 137 </li> 138 139 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/util.md">Edit on GitHub</a></li> 140 </ul> 141 </div> 142 <hr> 143 </header> 144 145 <details id="toc" open><summary>Table of contents</summary><ul> 146<li><span class="stability_2"><a href="#util_util">Util</a></span> 147<ul> 148<li><a href="#util_util_callbackify_original"><code>util.callbackify(original)</code></a></li> 149<li><a href="#util_util_debuglog_section_callback"><code>util.debuglog(section[, callback])</code></a> 150<ul> 151<li><a href="#util_debuglog_enabled"><code>debuglog().enabled</code></a></li> 152</ul> 153</li> 154<li><a href="#util_util_debug_section"><code>util.debug(section)</code></a></li> 155<li><a href="#util_util_deprecate_fn_msg_code"><code>util.deprecate(fn, msg[, code])</code></a></li> 156<li><a href="#util_util_format_format_args"><code>util.format(format[, ...args])</code></a></li> 157<li><a href="#util_util_formatwithoptions_inspectoptions_format_args"><code>util.formatWithOptions(inspectOptions, format[, ...args])</code></a></li> 158<li><a href="#util_util_getsystemerrorname_err"><code>util.getSystemErrorName(err)</code></a></li> 159<li><a href="#util_util_getsystemerrormap"><code>util.getSystemErrorMap()</code></a></li> 160<li><span class="stability_3"><a href="#util_util_inherits_constructor_superconstructor"><code>util.inherits(constructor, superConstructor)</code></a></span></li> 161<li><a href="#util_util_inspect_object_options"><code>util.inspect(object[, options])</code></a></li> 162<li><a href="#util_util_inspect_object_showhidden_depth_colors"><code>util.inspect(object[, showHidden[, depth[, colors]]])</code></a> 163<ul> 164<li><a href="#util_customizing_util_inspect_colors">Customizing <code>util.inspect</code> colors</a> 165<ul> 166<li><a href="#util_modifiers">Modifiers</a></li> 167<li><a href="#util_foreground_colors">Foreground colors</a></li> 168<li><a href="#util_background_colors">Background colors</a></li> 169</ul> 170</li> 171<li><a href="#util_custom_inspection_functions_on_objects">Custom inspection functions on objects</a></li> 172<li><a href="#util_util_inspect_custom"><code>util.inspect.custom</code></a></li> 173<li><a href="#util_util_inspect_defaultoptions"><code>util.inspect.defaultOptions</code></a></li> 174</ul> 175</li> 176<li><a href="#util_util_isdeepstrictequal_val1_val2"><code>util.isDeepStrictEqual(val1, val2)</code></a></li> 177<li><a href="#util_util_promisify_original"><code>util.promisify(original)</code></a> 178<ul> 179<li><a href="#util_custom_promisified_functions">Custom promisified functions</a></li> 180<li><a href="#util_util_promisify_custom"><code>util.promisify.custom</code></a></li> 181</ul> 182</li> 183<li><a href="#util_class_util_textdecoder">Class: <code>util.TextDecoder</code></a> 184<ul> 185<li><a href="#util_whatwg_supported_encodings">WHATWG supported encodings</a> 186<ul> 187<li><a href="#util_encodings_supported_by_default_with_full_icu_data">Encodings supported by default (with full ICU data)</a></li> 188<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> 189<li><a href="#util_encodings_supported_when_icu_is_disabled">Encodings supported when ICU is disabled</a></li> 190</ul> 191</li> 192<li><a href="#util_new_textdecoder_encoding_options"><code>new TextDecoder([encoding[, options]])</code></a></li> 193<li><a href="#util_textdecoder_decode_input_options"><code>textDecoder.decode([input[, options]])</code></a></li> 194<li><a href="#util_textdecoder_encoding"><code>textDecoder.encoding</code></a></li> 195<li><a href="#util_textdecoder_fatal"><code>textDecoder.fatal</code></a></li> 196<li><a href="#util_textdecoder_ignorebom"><code>textDecoder.ignoreBOM</code></a></li> 197</ul> 198</li> 199<li><a href="#util_class_util_textencoder">Class: <code>util.TextEncoder</code></a> 200<ul> 201<li><a href="#util_textencoder_encode_input"><code>textEncoder.encode([input])</code></a></li> 202<li><a href="#util_textencoder_encodeinto_src_dest"><code>textEncoder.encodeInto(src, dest)</code></a></li> 203<li><a href="#util_textencoder_encoding"><code>textEncoder.encoding</code></a></li> 204</ul> 205</li> 206<li><a href="#util_util_tousvstring_string"><code>util.toUSVString(string)</code></a></li> 207<li><a href="#util_util_types"><code>util.types</code></a> 208<ul> 209<li><a href="#util_util_types_isanyarraybuffer_value"><code>util.types.isAnyArrayBuffer(value)</code></a></li> 210<li><a href="#util_util_types_isarraybufferview_value"><code>util.types.isArrayBufferView(value)</code></a></li> 211<li><a href="#util_util_types_isargumentsobject_value"><code>util.types.isArgumentsObject(value)</code></a></li> 212<li><a href="#util_util_types_isarraybuffer_value"><code>util.types.isArrayBuffer(value)</code></a></li> 213<li><a href="#util_util_types_isasyncfunction_value"><code>util.types.isAsyncFunction(value)</code></a></li> 214<li><a href="#util_util_types_isbigint64array_value"><code>util.types.isBigInt64Array(value)</code></a></li> 215<li><a href="#util_util_types_isbiguint64array_value"><code>util.types.isBigUint64Array(value)</code></a></li> 216<li><a href="#util_util_types_isbooleanobject_value"><code>util.types.isBooleanObject(value)</code></a></li> 217<li><a href="#util_util_types_isboxedprimitive_value"><code>util.types.isBoxedPrimitive(value)</code></a></li> 218<li><a href="#util_util_types_isdataview_value"><code>util.types.isDataView(value)</code></a></li> 219<li><a href="#util_util_types_isdate_value"><code>util.types.isDate(value)</code></a></li> 220<li><a href="#util_util_types_isexternal_value"><code>util.types.isExternal(value)</code></a></li> 221<li><a href="#util_util_types_isfloat32array_value"><code>util.types.isFloat32Array(value)</code></a></li> 222<li><a href="#util_util_types_isfloat64array_value"><code>util.types.isFloat64Array(value)</code></a></li> 223<li><a href="#util_util_types_isgeneratorfunction_value"><code>util.types.isGeneratorFunction(value)</code></a></li> 224<li><a href="#util_util_types_isgeneratorobject_value"><code>util.types.isGeneratorObject(value)</code></a></li> 225<li><a href="#util_util_types_isint8array_value"><code>util.types.isInt8Array(value)</code></a></li> 226<li><a href="#util_util_types_isint16array_value"><code>util.types.isInt16Array(value)</code></a></li> 227<li><a href="#util_util_types_isint32array_value"><code>util.types.isInt32Array(value)</code></a></li> 228<li><a href="#util_util_types_ismap_value"><code>util.types.isMap(value)</code></a></li> 229<li><a href="#util_util_types_ismapiterator_value"><code>util.types.isMapIterator(value)</code></a></li> 230<li><a href="#util_util_types_ismodulenamespaceobject_value"><code>util.types.isModuleNamespaceObject(value)</code></a></li> 231<li><a href="#util_util_types_isnativeerror_value"><code>util.types.isNativeError(value)</code></a></li> 232<li><a href="#util_util_types_isnumberobject_value"><code>util.types.isNumberObject(value)</code></a></li> 233<li><a href="#util_util_types_ispromise_value"><code>util.types.isPromise(value)</code></a></li> 234<li><a href="#util_util_types_isproxy_value"><code>util.types.isProxy(value)</code></a></li> 235<li><a href="#util_util_types_isregexp_value"><code>util.types.isRegExp(value)</code></a></li> 236<li><a href="#util_util_types_isset_value"><code>util.types.isSet(value)</code></a></li> 237<li><a href="#util_util_types_issetiterator_value"><code>util.types.isSetIterator(value)</code></a></li> 238<li><a href="#util_util_types_issharedarraybuffer_value"><code>util.types.isSharedArrayBuffer(value)</code></a></li> 239<li><a href="#util_util_types_isstringobject_value"><code>util.types.isStringObject(value)</code></a></li> 240<li><a href="#util_util_types_issymbolobject_value"><code>util.types.isSymbolObject(value)</code></a></li> 241<li><a href="#util_util_types_istypedarray_value"><code>util.types.isTypedArray(value)</code></a></li> 242<li><a href="#util_util_types_isuint8array_value"><code>util.types.isUint8Array(value)</code></a></li> 243<li><a href="#util_util_types_isuint8clampedarray_value"><code>util.types.isUint8ClampedArray(value)</code></a></li> 244<li><a href="#util_util_types_isuint16array_value"><code>util.types.isUint16Array(value)</code></a></li> 245<li><a href="#util_util_types_isuint32array_value"><code>util.types.isUint32Array(value)</code></a></li> 246<li><a href="#util_util_types_isweakmap_value"><code>util.types.isWeakMap(value)</code></a></li> 247<li><a href="#util_util_types_isweakset_value"><code>util.types.isWeakSet(value)</code></a></li> 248<li><span class="stability_0"><a href="#util_util_types_iswebassemblycompiledmodule_value"><code>util.types.isWebAssemblyCompiledModule(value)</code></a></span></li> 249</ul> 250</li> 251<li><a href="#util_deprecated_apis">Deprecated APIs</a> 252<ul> 253<li><span class="stability_0"><a href="#util_util_extend_target_source"><code>util._extend(target, source)</code></a></span></li> 254<li><span class="stability_0"><a href="#util_util_isarray_object"><code>util.isArray(object)</code></a></span></li> 255<li><span class="stability_0"><a href="#util_util_isboolean_object"><code>util.isBoolean(object)</code></a></span></li> 256<li><span class="stability_0"><a href="#util_util_isbuffer_object"><code>util.isBuffer(object)</code></a></span></li> 257<li><span class="stability_0"><a href="#util_util_isdate_object"><code>util.isDate(object)</code></a></span></li> 258<li><span class="stability_0"><a href="#util_util_iserror_object"><code>util.isError(object)</code></a></span></li> 259<li><span class="stability_0"><a href="#util_util_isfunction_object"><code>util.isFunction(object)</code></a></span></li> 260<li><span class="stability_0"><a href="#util_util_isnull_object"><code>util.isNull(object)</code></a></span></li> 261<li><span class="stability_0"><a href="#util_util_isnullorundefined_object"><code>util.isNullOrUndefined(object)</code></a></span></li> 262<li><span class="stability_0"><a href="#util_util_isnumber_object"><code>util.isNumber(object)</code></a></span></li> 263<li><span class="stability_0"><a href="#util_util_isobject_object"><code>util.isObject(object)</code></a></span></li> 264<li><span class="stability_0"><a href="#util_util_isprimitive_object"><code>util.isPrimitive(object)</code></a></span></li> 265<li><span class="stability_0"><a href="#util_util_isregexp_object"><code>util.isRegExp(object)</code></a></span></li> 266<li><span class="stability_0"><a href="#util_util_isstring_object"><code>util.isString(object)</code></a></span></li> 267<li><span class="stability_0"><a href="#util_util_issymbol_object"><code>util.isSymbol(object)</code></a></span></li> 268<li><span class="stability_0"><a href="#util_util_isundefined_object"><code>util.isUndefined(object)</code></a></span></li> 269<li><span class="stability_0"><a href="#util_util_log_string"><code>util.log(string)</code></a></span></li> 270</ul> 271</li> 272</ul> 273</li> 274</ul></details> 275 276 <div id="apicontent"> 277 <h2>Util<span><a class="mark" href="#util_util" id="util_util">#</a></span></h2> 278 279<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 280<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v14.21.2/lib/util.js">lib/util.js</a></p> 281<p>The <code>util</code> module supports the needs of Node.js internal APIs. Many of the 282utilities are useful for application and module developers as well. To access 283it:</p> 284<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> 285<section><h3><code>util.callbackify(original)</code><span><a class="mark" href="#util_util_callbackify_original" id="util_util_callbackify_original">#</a></span></h3> 286<div class="api_metadata"> 287<span>Added in: v8.2.0</span> 288</div> 289<ul> 290<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> 291<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> 292</ul> 293<p>Takes an <code>async</code> function (or a function that returns a <code>Promise</code>) and returns a 294function following the error-first callback style, i.e. taking 295an <code>(err, value) => ...</code> callback as the last argument. In the callback, the 296first argument will be the rejection reason (or <code>null</code> if the <code>Promise</code> 297resolved), and the second argument will be the resolved value.</p> 298<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>); 299 300<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">fn</span>(<span class="hljs-params"></span>) { 301 <span class="hljs-keyword">return</span> <span class="hljs-string">'hello world'</span>; 302} 303<span class="hljs-keyword">const</span> callbackFunction = util.<span class="hljs-title function_">callbackify</span>(fn); 304 305<span class="hljs-title function_">callbackFunction</span>(<span class="hljs-function">(<span class="hljs-params">err, ret</span>) =></span> { 306 <span class="hljs-keyword">if</span> (err) <span class="hljs-keyword">throw</span> err; 307 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(ret); 308});</code></pre> 309<p>Will print:</p> 310<pre><code class="language-text">hello world</code></pre> 311<p>The callback is executed asynchronously, and will have a limited stack trace. 312If the callback throws, the process will emit an <a href="process.html#process_event_uncaughtexception"><code>'uncaughtException'</code></a> 313event, and if not handled will exit.</p> 314<p>Since <code>null</code> has a special meaning as the first argument to a callback, if a 315wrapped function rejects a <code>Promise</code> with a falsy value as a reason, the value 316is wrapped in an <code>Error</code> with the original value stored in a field named 317<code>reason</code>.</p> 318<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">fn</span>(<span class="hljs-params"></span>) { 319 <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>); 320} 321<span class="hljs-keyword">const</span> callbackFunction = util.<span class="hljs-title function_">callbackify</span>(fn); 322 323<span class="hljs-title function_">callbackFunction</span>(<span class="hljs-function">(<span class="hljs-params">err, ret</span>) =></span> { 324 <span class="hljs-comment">// When the Promise was rejected with `null` it is wrapped with an Error and</span> 325 <span class="hljs-comment">// the original value is stored in `reason`.</span> 326 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> 327});</code></pre> 328</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> 329<div class="api_metadata"> 330<span>Added in: v0.11.3</span> 331</div> 332<ul> 333<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 334which the <code>debuglog</code> function is being created.</li> 335<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 336is called with a function argument that is a more optimized logging function.</li> 337<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> 338</ul> 339<p>The <code>util.debuglog()</code> method is used to create a function that conditionally 340writes debug messages to <code>stderr</code> based on the existence of the <code>NODE_DEBUG</code> 341environment variable. If the <code>section</code> name appears within the value of that 342environment variable, then the returned function operates similar to 343<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> 344<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>); 345<span class="hljs-keyword">const</span> debuglog = util.<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'foo'</span>); 346 347<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'hello from foo [%d]'</span>, <span class="hljs-number">123</span>);</code></pre> 348<p>If this program is run with <code>NODE_DEBUG=foo</code> in the environment, then 349it will output something like:</p> 350<pre><code class="language-console">FOO 3245: hello from foo [123]</code></pre> 351<p>where <code>3245</code> is the process id. If it is not run with that 352environment variable set, then it will not print anything.</p> 353<p>The <code>section</code> supports wildcard also:</p> 354<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>); 355<span class="hljs-keyword">const</span> debuglog = util.<span class="hljs-title function_">debuglog</span>(<span class="hljs-string">'foo-bar'</span>); 356 357<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> 358<p>if it is run with <code>NODE_DEBUG=foo*</code> in the environment, then it will output 359something like:</p> 360<pre><code class="language-console">FOO-BAR 3257: hi there, it's foo-bar [2333]</code></pre> 361<p>Multiple comma-separated <code>section</code> names may be specified in the <code>NODE_DEBUG</code> 362environment variable: <code>NODE_DEBUG=fs,net,tls</code>.</p> 363<p>The optional <code>callback</code> argument can be used to replace the logging function 364with a different function that doesn't have any initialization or 365unnecessary wrapping.</p> 366<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>); 367<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> { 368 <span class="hljs-comment">// Replace with a logging function that optimizes out</span> 369 <span class="hljs-comment">// testing if the section is enabled</span> 370 debuglog = debug; 371});</code></pre> 372<h4><code>debuglog().enabled</code><span><a class="mark" href="#util_debuglog_enabled" id="util_debuglog_enabled">#</a></span></h4> 373<div class="api_metadata"> 374<span>Added in: v14.9.0</span> 375</div> 376<ul> 377<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 378</ul> 379<p>The <code>util.debuglog().enabled</code> getter is used to create a test that can be used 380in conditionals based on the existence of the <code>NODE_DEBUG</code> environment variable. 381If the <code>section</code> name appears within the value of that environment variable, 382then the returned value will be <code>true</code>. If not, then the returned value will be 383<code>false</code>.</p> 384<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>); 385<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>; 386<span class="hljs-keyword">if</span> (enabled) { 387 <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>); 388}</code></pre> 389<p>If this program is run with <code>NODE_DEBUG=foo</code> in the environment, then it will 390output something like:</p> 391<pre><code class="language-console">hello from foo [123]</code></pre> 392</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> 393<div class="api_metadata"> 394<span>Added in: v14.9.0</span> 395</div> 396<p>Alias for <code>util.debuglog</code>. Usage allows for readability of that doesn't imply 397logging when only using <code>util.debuglog().enabled</code>.</p> 398</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> 399<div class="api_metadata"> 400<details class="changelog"><summary>History</summary> 401<table> 402<tbody><tr><th>Version</th><th>Changes</th></tr> 403<tr><td>v10.0.0</td> 404<td><p>Deprecation warnings are only emitted once for each code.</p></td></tr> 405<tr><td>v0.8.0</td> 406<td><p><span>Added in: v0.8.0</span></p></td></tr> 407</tbody></table> 408</details> 409</div> 410<ul> 411<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> 412<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 413invoked.</li> 414<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 415list of codes.</li> 416<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> 417</ul> 418<p>The <code>util.deprecate()</code> method wraps <code>fn</code> (which may be a function or class) in 419such a way that it is marked as deprecated.</p> 420<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>); 421 422<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> { 423 <span class="hljs-comment">// Do something here.</span> 424}, <span class="hljs-string">'obsoleteFunction() is deprecated. Use newShinyFunction() instead.'</span>);</code></pre> 425<p>When called, <code>util.deprecate()</code> will return a function that will emit a 426<code>DeprecationWarning</code> using the <a href="process.html#process_event_warning"><code>'warning'</code></a> event. The warning will 427be emitted and printed to <code>stderr</code> the first time the returned function is 428called. After the warning is emitted, the wrapped function is called without 429emitting a warning.</p> 430<p>If the same optional <code>code</code> is supplied in multiple calls to <code>util.deprecate()</code>, 431the warning will be emitted only once for that <code>code</code>.</p> 432<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>); 433 434<span class="hljs-keyword">const</span> fn1 = util.<span class="hljs-title function_">deprecate</span>(someFunction, someMessage, <span class="hljs-string">'DEP0001'</span>); 435<span class="hljs-keyword">const</span> fn2 = util.<span class="hljs-title function_">deprecate</span>(someOtherFunction, someOtherMessage, <span class="hljs-string">'DEP0001'</span>); 436<span class="hljs-title function_">fn1</span>(); <span class="hljs-comment">// Emits a deprecation warning with code DEP0001</span> 437<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> 438<p>If either the <code>--no-deprecation</code> or <code>--no-warnings</code> command-line flags are 439used, or if the <code>process.noDeprecation</code> property is set to <code>true</code> <em>prior</em> to 440the first deprecation warning, the <code>util.deprecate()</code> method does nothing.</p> 441<p>If the <code>--trace-deprecation</code> or <code>--trace-warnings</code> command-line flags are set, 442or the <code>process.traceDeprecation</code> property is set to <code>true</code>, a warning and a 443stack trace are printed to <code>stderr</code> the first time the deprecated function is 444called.</p> 445<p>If the <code>--throw-deprecation</code> command-line flag is set, or the 446<code>process.throwDeprecation</code> property is set to <code>true</code>, then an exception will be 447thrown when the deprecated function is called.</p> 448<p>The <code>--throw-deprecation</code> command-line flag and <code>process.throwDeprecation</code> 449property take precedence over <code>--trace-deprecation</code> and 450<code>process.traceDeprecation</code>.</p> 451</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> 452<div class="api_metadata"> 453<details class="changelog"><summary>History</summary> 454<table> 455<tbody><tr><th>Version</th><th>Changes</th></tr> 456<tr><td>v12.11.0</td> 457<td><p>The <code>%c</code> specifier is ignored now.</p></td></tr> 458<tr><td>v12.0.0</td> 459<td><p>The <code>format</code> argument is now only taken as such if it actually contains format specifiers.</p></td></tr> 460<tr><td>v12.0.0</td> 461<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> 462<tr><td>v11.4.0</td> 463<td><p>The <code>%d</code>, <code>%f</code> and <code>%i</code> specifiers now support Symbols properly.</p></td></tr> 464<tr><td>v11.4.0</td> 465<td><p>The <code>%o</code> specifier's <code>depth</code> has default depth of 4 again.</p></td></tr> 466<tr><td>v11.0.0</td> 467<td><p>The <code>%o</code> specifier's <code>depth</code> option will now fall back to the default depth.</p></td></tr> 468<tr><td>v10.12.0</td> 469<td><p>The <code>%d</code> and <code>%i</code> specifiers now support BigInt.</p></td></tr> 470<tr><td>v8.4.0</td> 471<td><p>The <code>%o</code> and <code>%O</code> specifiers are supported now.</p></td></tr> 472<tr><td>v0.5.3</td> 473<td><p><span>Added in: v0.5.3</span></p></td></tr> 474</tbody></table> 475</details> 476</div> 477<ul> 478<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> 479</ul> 480<p>The <code>util.format()</code> method returns a formatted string using the first argument 481as a <code>printf</code>-like format string which can contain zero or more format 482specifiers. Each specifier is replaced with the converted value from the 483corresponding argument. Supported specifiers are:</p> 484<ul> 485<li><code>%s</code>: <code>String</code> will be used to convert all values except <code>BigInt</code>, <code>Object</code> 486and <code>-0</code>. <code>BigInt</code> values will be represented with an <code>n</code> and Objects that 487have no user defined <code>toString</code> function are inspected using <code>util.inspect()</code> 488with options <code>{ depth: 0, colors: false, compact: 3 }</code>.</li> 489<li><code>%d</code>: <code>Number</code> will be used to convert all values except <code>BigInt</code> and 490<code>Symbol</code>.</li> 491<li><code>%i</code>: <code>parseInt(value, 10)</code> is used for all values except <code>BigInt</code> and 492<code>Symbol</code>.</li> 493<li><code>%f</code>: <code>parseFloat(value)</code> is used for all values expect <code>Symbol</code>.</li> 494<li><code>%j</code>: JSON. Replaced with the string <code>'[Circular]'</code> if the argument contains 495circular references.</li> 496<li><code>%o</code>: <code>Object</code>. A string representation of an object with generic JavaScript 497object formatting. Similar to <code>util.inspect()</code> with options 498<code>{ showHidden: true, showProxy: true }</code>. This will show the full object 499including non-enumerable properties and proxies.</li> 500<li><code>%O</code>: <code>Object</code>. A string representation of an object with generic JavaScript 501object formatting. Similar to <code>util.inspect()</code> without options. This will show 502the full object not including non-enumerable properties and proxies.</li> 503<li><code>%c</code>: <code>CSS</code>. This specifier is ignored and will skip any CSS passed in.</li> 504<li><code>%%</code>: single percent sign (<code>'%'</code>). This does not consume an argument.</li> 505<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> 506</ul> 507<p>If a specifier does not have a corresponding argument, it is not replaced:</p> 508<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>); 509<span class="hljs-comment">// Returns: 'foo:%s'</span></code></pre> 510<p>Values that are not part of the format string are formatted using 511<code>util.inspect()</code> if their type is not <code>string</code>.</p> 512<p>If there are more arguments passed to the <code>util.format()</code> method than the 513number of specifiers, the extra arguments are concatenated to the returned 514string, separated by spaces:</p> 515<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>); 516<span class="hljs-comment">// Returns: 'foo:bar baz'</span></code></pre> 517<p>If the first argument does not contain a valid format specifier, <code>util.format()</code> 518returns a string that is the concatenation of all arguments separated by spaces:</p> 519<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>); 520<span class="hljs-comment">// Returns: '1 2 3'</span></code></pre> 521<p>If only one argument is passed to <code>util.format()</code>, it is returned as it is 522without any formatting:</p> 523<pre><code class="language-js">util.<span class="hljs-title function_">format</span>(<span class="hljs-string">'%% %s'</span>); 524<span class="hljs-comment">// Returns: '%% %s'</span></code></pre> 525<p><code>util.format()</code> is a synchronous method that is intended as a debugging tool. 526Some input values can have a significant performance overhead that can block the 527event loop. Use this function with care and never in a hot code path.</p> 528</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> 529<div class="api_metadata"> 530<span>Added in: v10.0.0</span> 531</div> 532<ul> 533<li><code>inspectOptions</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 534<li><code>format</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 535</ul> 536<p>This function is identical to <a href="#util_util_format_format_args"><code>util.format()</code></a>, except in that it takes 537an <code>inspectOptions</code> argument which specifies options that are passed along to 538<a href="#util_util_inspect_object_options"><code>util.inspect()</code></a>.</p> 539<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> }); 540<span class="hljs-comment">// Returns 'See object { foo: 42 }', where `42` is colored as a number</span> 541<span class="hljs-comment">// when printed to a terminal.</span></code></pre> 542</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> 543<div class="api_metadata"> 544<span>Added in: v9.7.0</span> 545</div> 546<ul> 547<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 548<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 549</ul> 550<p>Returns the string name for a numeric error code that comes from a Node.js API. 551The mapping between error codes and error names is platform-dependent. 552See <a href="errors.html#errors_common_system_errors">Common System Errors</a> for the names of common errors.</p> 553<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> { 554 <span class="hljs-keyword">const</span> name = util.<span class="hljs-title function_">getSystemErrorName</span>(err.<span class="hljs-property">errno</span>); 555 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(name); <span class="hljs-comment">// ENOENT</span> 556});</code></pre> 557</section><section><h3><code>util.getSystemErrorMap()</code><span><a class="mark" href="#util_util_getsystemerrormap" id="util_util_getsystemerrormap">#</a></span></h3> 558<div class="api_metadata"> 559<span>Added in: v14.17.0</span> 560</div> 561<ul> 562<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map" class="type"><Map></a></li> 563</ul> 564<p>Returns a Map of all system error codes available from the Node.js API. 565The mapping between error codes and error names is platform-dependent. 566See <a href="errors.html#errors_common_system_errors">Common System Errors</a> for the names of common errors.</p> 567<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> { 568 <span class="hljs-keyword">const</span> errorMap = util.<span class="hljs-title function_">getSystemErrorMap</span>(); 569 <span class="hljs-keyword">const</span> name = errorMap.<span class="hljs-title function_">get</span>(err.<span class="hljs-property">errno</span>); 570 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">error</span>(name); <span class="hljs-comment">// ENOENT</span> 571});</code></pre> 572</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> 573<div class="api_metadata"> 574<details class="changelog"><summary>History</summary> 575<table> 576<tbody><tr><th>Version</th><th>Changes</th></tr> 577<tr><td>v5.0.0</td> 578<td><p>The <code>constructor</code> parameter can refer to an ES6 class now.</p></td></tr> 579<tr><td>v0.3.0</td> 580<td><p><span>Added in: v0.3.0</span></p></td></tr> 581</tbody></table> 582</details> 583</div> 584<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> 585<ul> 586<li><code>constructor</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 587<li><code>superConstructor</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 588</ul> 589<p>Usage of <code>util.inherits()</code> is discouraged. Please use the ES6 <code>class</code> and 590<code>extends</code> keywords to get language level inheritance support. Also note 591that the two styles are <a href="https://github.com/nodejs/node/issues/4179">semantically incompatible</a>.</p> 592<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 593prototype of <code>constructor</code> will be set to a new object created from 594<code>superConstructor</code>.</p> 595<p>This mainly adds some input validation on top of 596<code>Object.setPrototypeOf(constructor.prototype, superConstructor.prototype)</code>. 597As an additional convenience, <code>superConstructor</code> will be accessible 598through the <code>constructor.super_</code> property.</p> 599<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>); 600<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>); 601 602<span class="hljs-keyword">function</span> <span class="hljs-title function_">MyStream</span>(<span class="hljs-params"></span>) { 603 <span class="hljs-title class_">EventEmitter</span>.<span class="hljs-title function_">call</span>(<span class="hljs-variable language_">this</span>); 604} 605 606util.<span class="hljs-title function_">inherits</span>(<span class="hljs-title class_">MyStream</span>, <span class="hljs-title class_">EventEmitter</span>); 607 608<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>) { 609 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">emit</span>(<span class="hljs-string">'data'</span>, data); 610}; 611 612<span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyStream</span>(); 613 614<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> 615<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> 616 617stream.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 618 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received data: "<span class="hljs-subst">${data}</span>"`</span>); 619}); 620stream.<span class="hljs-title function_">write</span>(<span class="hljs-string">'It works!'</span>); <span class="hljs-comment">// Received data: "It works!"</span></code></pre> 621<p>ES6 example using <code>class</code> and <code>extends</code>:</p> 622<pre><code class="language-js"><span class="hljs-keyword">const</span> <span class="hljs-title class_">EventEmitter</span> = <span class="hljs-built_in">require</span>(<span class="hljs-string">'events'</span>); 623 624<span class="hljs-keyword">class</span> <span class="hljs-title class_">MyStream</span> <span class="hljs-keyword">extends</span> <span class="hljs-title class_ inherited__">EventEmitter</span> { 625 <span class="hljs-title function_">write</span>(<span class="hljs-params">data</span>) { 626 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">emit</span>(<span class="hljs-string">'data'</span>, data); 627 } 628} 629 630<span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MyStream</span>(); 631 632stream.<span class="hljs-title function_">on</span>(<span class="hljs-string">'data'</span>, <span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { 633 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`Received data: "<span class="hljs-subst">${data}</span>"`</span>); 634}); 635stream.<span class="hljs-title function_">write</span>(<span class="hljs-string">'With ES6'</span>);</code></pre> 636</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> 637</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> 638<div class="api_metadata"> 639<details class="changelog"><summary>History</summary> 640<table> 641<tbody><tr><th>Version</th><th>Changes</th></tr> 642<tr><td>v13.0.0</td> 643<td><p>Circular references now include a marker to the reference.</p></td></tr> 644<tr><td>v14.6.0, v12.19.0</td> 645<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> 646<tr><td>v13.13.0, v12.17.0</td> 647<td><p>The <code>maxStringLength</code> option is supported now.</p></td></tr> 648<tr><td>v13.5.0, v12.16.0</td> 649<td><p>User defined prototype properties are inspected in case <code>showHidden</code> is <code>true</code>.</p></td></tr> 650<tr><td>v12.0.0</td> 651<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> 652<tr><td>v12.0.0</td> 653<td><p>Internal properties no longer appear in the context argument of a custom inspection function.</p></td></tr> 654<tr><td>v11.11.0</td> 655<td><p>The <code>compact</code> option accepts numbers for a new output mode.</p></td></tr> 656<tr><td>v11.7.0</td> 657<td><p>ArrayBuffers now also show their binary contents.</p></td></tr> 658<tr><td>v11.5.0</td> 659<td><p>The <code>getters</code> option is supported now.</p></td></tr> 660<tr><td>v11.4.0</td> 661<td><p>The <code>depth</code> default changed back to <code>2</code>.</p></td></tr> 662<tr><td>v11.0.0</td> 663<td><p>The <code>depth</code> default changed to <code>20</code>.</p></td></tr> 664<tr><td>v11.0.0</td> 665<td><p>The inspection output is now limited to about 128 MB. Data above that size will not be fully inspected.</p></td></tr> 666<tr><td>v10.12.0</td> 667<td><p>The <code>sorted</code> option is supported now.</p></td></tr> 668<tr><td>v10.6.0</td> 669<td><p>Inspecting linked lists and similar objects is now possible up to the maximum call stack size.</p></td></tr> 670<tr><td>v10.0.0</td> 671<td><p>The <code>WeakMap</code> and <code>WeakSet</code> entries can now be inspected as well.</p></td></tr> 672<tr><td>v9.9.0</td> 673<td><p>The <code>compact</code> option is supported now.</p></td></tr> 674<tr><td>v6.6.0</td> 675<td><p>Custom inspection functions can now return <code>this</code>.</p></td></tr> 676<tr><td>v6.3.0</td> 677<td><p>The <code>breakLength</code> option is supported now.</p></td></tr> 678<tr><td>v6.1.0</td> 679<td><p>The <code>maxArrayLength</code> option is supported now; in particular, long arrays are truncated by default.</p></td></tr> 680<tr><td>v6.1.0</td> 681<td><p>The <code>showProxy</code> option is supported now.</p></td></tr> 682<tr><td>v0.3.0</td> 683<td><p><span>Added in: v0.3.0</span></p></td></tr> 684</tbody></table> 685</details> 686</div> 687<ul> 688<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> 689<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 690<ul> 691<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 692properties 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 693<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 694properties (excluding method properties). <strong>Default:</strong> <code>false</code>.</li> 695<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 696<code>object</code>. This is useful for inspecting large objects. To recurse up to 697the maximum call stack size pass <code>Infinity</code> or <code>null</code>. 698<strong>Default:</strong> <code>2</code>.</li> 699<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 700codes. Colors are customizable. See <a href="#util_customizing_util_inspect_colors">Customizing <code>util.inspect</code> colors</a>. 701<strong>Default:</strong> <code>false</code>.</li> 702<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>, 703<code>[util.inspect.custom](depth, opts)</code> functions are not invoked. 704<strong>Default:</strong> <code>true</code>.</li> 705<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 706the <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> 707<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>, 708<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 709formatting. Set to <code>null</code> or <code>Infinity</code> to show all elements. Set to <code>0</code> or 710negative to show no elements. <strong>Default:</strong> <code>100</code>.</li> 711<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 712include when formatting. Set to <code>null</code> or <code>Infinity</code> to show all elements. 713Set to <code>0</code> or negative to show no characters. <strong>Default:</strong> <code>Infinity</code>.</li> 714<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 715multiple lines. Set to <code>Infinity</code> to format the input as a single line 716(in combination with <code>compact</code> set to <code>true</code> or any number >= <code>1</code>). 717<strong>Default:</strong> <code>80</code>.</li> 718<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 719to be displayed on a new line. It will also add new lines to text that is 720longer than <code>breakLength</code>. If set to a number, the most <code>n</code> inner elements 721are united on a single line as long as all properties fit into 722<code>breakLength</code>. Short array elements are also grouped together. No 723text will be reduced below 16 characters, no matter the <code>breakLength</code> size. 724For more information, see the example below. <strong>Default:</strong> <code>3</code>.</li> 725<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 726of an object, and <code>Set</code> and <code>Map</code> entries are sorted in the resulting 727string. 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, 728it 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> 729<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 730to <code>'get'</code>, only getters without a corresponding setter are inspected. If 731set to <code>'set'</code>, only getters with a corresponding setter are inspected. 732This might cause side effects depending on the getter function. 733<strong>Default:</strong> <code>false</code>.</li> 734</ul> 735</li> 736<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> 737</ul> 738<p>The <code>util.inspect()</code> method returns a string representation of <code>object</code> that is 739intended for debugging. The output of <code>util.inspect</code> may change at any time 740and should not be depended upon programmatically. Additional <code>options</code> may be 741passed that alter the result. 742<code>util.inspect()</code> will use the constructor's name and/or <code>@@toStringTag</code> to make 743an identifiable tag for an inspected value.</p> 744<pre><code class="language-js"><span class="hljs-keyword">class</span> <span class="hljs-title class_">Foo</span> { 745 get [<span class="hljs-title class_">Symbol</span>.<span class="hljs-property">toStringTag</span>]() { 746 <span class="hljs-keyword">return</span> <span class="hljs-string">'bar'</span>; 747 } 748} 749 750<span class="hljs-keyword">class</span> <span class="hljs-title class_">Bar</span> {} 751 752<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> } }); 753 754util.<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> 755util.<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> 756util.<span class="hljs-title function_">inspect</span>(baz); <span class="hljs-comment">// '[foo] {}'</span></code></pre> 757<p>Circular references point to their anchor by using a reference index:</p> 758<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>); 759 760<span class="hljs-keyword">const</span> obj = {}; 761obj.<span class="hljs-property">a</span> = [obj]; 762obj.<span class="hljs-property">b</span> = {}; 763obj.<span class="hljs-property">b</span>.<span class="hljs-property">inner</span> = obj.<span class="hljs-property">b</span>; 764obj.<span class="hljs-property">b</span>.<span class="hljs-property">obj</span> = obj; 765 766<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">inspect</span>(obj)); 767<span class="hljs-comment">// <ref *1> {</span> 768<span class="hljs-comment">// a: [ [Circular *1] ],</span> 769<span class="hljs-comment">// b: <ref *2> { inner: [Circular *2], obj: [Circular *1] }</span> 770<span class="hljs-comment">// }</span></code></pre> 771<p>The following example inspects all properties of the <code>util</code> object:</p> 772<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>); 773 774<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> 775<p>The following example highlights the effect of the <code>compact</code> option:</p> 776<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>); 777 778<span class="hljs-keyword">const</span> o = { 779 <span class="hljs-attr">a</span>: [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, [[ 780 <span class="hljs-string">'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do '</span> + 781 <span class="hljs-string">'eiusmod tempor incididunt ut labore et dolore magna aliqua.'</span>, 782 <span class="hljs-string">'test'</span>, 783 <span class="hljs-string">'foo'</span>]], <span class="hljs-number">4</span>], 784 <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>]]) 785}; 786<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> })); 787 788<span class="hljs-comment">// { a:</span> 789<span class="hljs-comment">// [ 1,</span> 790<span class="hljs-comment">// 2,</span> 791<span class="hljs-comment">// [ [ 'Lorem ipsum dolor sit amet, consectetur [...]', // A long line</span> 792<span class="hljs-comment">// 'test',</span> 793<span class="hljs-comment">// 'foo' ] ],</span> 794<span class="hljs-comment">// 4 ],</span> 795<span class="hljs-comment">// b: Map(2) { 'za' => 1, 'zb' => 'test' } }</span> 796 797<span class="hljs-comment">// Setting `compact` to false changes the output to be more reader friendly.</span> 798<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> })); 799 800<span class="hljs-comment">// {</span> 801<span class="hljs-comment">// a: [</span> 802<span class="hljs-comment">// 1,</span> 803<span class="hljs-comment">// 2,</span> 804<span class="hljs-comment">// [</span> 805<span class="hljs-comment">// [</span> 806<span class="hljs-comment">// 'Lorem ipsum dolor sit amet, consectetur ' +</span> 807<span class="hljs-comment">// 'adipiscing elit, sed do eiusmod tempor ' +</span> 808<span class="hljs-comment">// 'incididunt ut labore et dolore magna ' +</span> 809<span class="hljs-comment">// 'aliqua.,</span> 810<span class="hljs-comment">// 'test',</span> 811<span class="hljs-comment">// 'foo'</span> 812<span class="hljs-comment">// ]</span> 813<span class="hljs-comment">// ],</span> 814<span class="hljs-comment">// 4</span> 815<span class="hljs-comment">// ],</span> 816<span class="hljs-comment">// b: Map(2) {</span> 817<span class="hljs-comment">// 'za' => 1,</span> 818<span class="hljs-comment">// 'zb' => 'test'</span> 819<span class="hljs-comment">// }</span> 820<span class="hljs-comment">// }</span> 821 822<span class="hljs-comment">// Setting `breakLength` to e.g. 150 will print the "Lorem ipsum" text in a</span> 823<span class="hljs-comment">// single line.</span> 824<span class="hljs-comment">// Reducing the `breakLength` will split the "Lorem ipsum" text in smaller</span> 825<span class="hljs-comment">// chunks.</span></code></pre> 826<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 827inspected. If there are more entries than <code>maxArrayLength</code>, there is no 828guarantee which entries are displayed. That means retrieving the same 829<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 830with no remaining strong references may be garbage collected at any time.</p> 831<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>); 832 833<span class="hljs-keyword">const</span> obj = { <span class="hljs-attr">a</span>: <span class="hljs-number">1</span> }; 834<span class="hljs-keyword">const</span> obj2 = { <span class="hljs-attr">b</span>: <span class="hljs-number">2</span> }; 835<span class="hljs-keyword">const</span> weakSet = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakSet</span>([obj, obj2]); 836 837<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> })); 838<span class="hljs-comment">// WeakSet { { a: 1 }, { b: 2 } }</span></code></pre> 839<p>The <code>sorted</code> option ensures that an object's property insertion order does not 840impact the result of <code>util.inspect()</code>.</p> 841<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>); 842<span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'assert'</span>); 843 844<span class="hljs-keyword">const</span> o1 = { 845 <span class="hljs-attr">b</span>: [<span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">1</span>], 846 <span class="hljs-attr">a</span>: <span class="hljs-string">'`a` comes before `b`'</span>, 847 <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>]) 848}; 849<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> })); 850<span class="hljs-comment">// { a: '`a` comes before `b`', b: [ 2, 3, 1 ], c: Set(3) { 1, 2, 3 } }</span> 851<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) })); 852<span class="hljs-comment">// { c: Set(3) { 3, 2, 1 }, b: [ 2, 3, 1 ], a: '`a` comes before `b`' }</span> 853 854<span class="hljs-keyword">const</span> o2 = { 855 <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>]), 856 <span class="hljs-attr">a</span>: <span class="hljs-string">'`a` comes before `b`'</span>, 857 <span class="hljs-attr">b</span>: [<span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">1</span>] 858}; 859assert.<span class="hljs-property">strict</span>.<span class="hljs-title function_">equal</span>( 860 <span class="hljs-title function_">inspect</span>(o1, { <span class="hljs-attr">sorted</span>: <span class="hljs-literal">true</span> }), 861 <span class="hljs-title function_">inspect</span>(o2, { <span class="hljs-attr">sorted</span>: <span class="hljs-literal">true</span> }) 862);</code></pre> 863<p><code>util.inspect()</code> is a synchronous method intended for debugging. Its maximum 864output length is approximately 128 MB. Inputs that result in longer output will 865be truncated.</p> 866<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> 867 868<p>Color output (if enabled) of <code>util.inspect</code> is customizable globally 869via the <code>util.inspect.styles</code> and <code>util.inspect.colors</code> properties.</p> 870<p><code>util.inspect.styles</code> is a map associating a style name to a color from 871<code>util.inspect.colors</code>.</p> 872<p>The default styles and associated colors are:</p> 873<ul> 874<li><code>bigint</code>: <code>yellow</code></li> 875<li><code>boolean</code>: <code>yellow</code></li> 876<li><code>date</code>: <code>magenta</code></li> 877<li><code>module</code>: <code>underline</code></li> 878<li><code>name</code>: (no styling)</li> 879<li><code>null</code>: <code>bold</code></li> 880<li><code>number</code>: <code>yellow</code></li> 881<li><code>regexp</code>: <code>red</code></li> 882<li><code>special</code>: <code>cyan</code> (e.g., <code>Proxies</code>)</li> 883<li><code>string</code>: <code>green</code></li> 884<li><code>symbol</code>: <code>green</code></li> 885<li><code>undefined</code>: <code>grey</code></li> 886</ul> 887<p>Color styling uses ANSI control codes that may not be supported on all 888terminals. To verify color support use <a href="tty.html#tty_writestream_hascolors_count_env"><code>tty.hasColors()</code></a>.</p> 889<p>Predefined control codes are listed below (grouped as "Modifiers", "Foreground 890colors", and "Background colors").</p> 891<h5>Modifiers<span><a class="mark" href="#util_modifiers" id="util_modifiers">#</a></span></h5> 892<p>Modifier support varies throughout different terminals. They will mostly be 893ignored, if not supported.</p> 894<ul> 895<li><code>reset</code> - Resets all (color) modifiers to their defaults</li> 896<li><strong>bold</strong> - Make text bold</li> 897<li><em>italic</em> - Make text italic</li> 898<li><span style="border-bottom: 1px;">underline</span> - Make text underlined</li> 899<li><del>strikethrough</del> - Puts a horizontal line through the center of the text 900(Alias: <code>strikeThrough</code>, <code>crossedout</code>, <code>crossedOut</code>)</li> 901<li><code>hidden</code> - Prints the text, but makes it invisible (Alias: conceal)</li> 902<li><span style="opacity: 0.5;">dim</span> - Decreased color intensity (Alias: 903<code>faint</code>)</li> 904<li><span style="border-top: 1px">overlined</span> - Make text overlined</li> 905<li>blink - Hides and shows the text in an interval</li> 906<li><span style="filter: invert(100%)">inverse</span> - Swap foreground and 907background colors (Alias: <code>swapcolors</code>, <code>swapColors</code>)</li> 908<li><span style="border-bottom: 1px double;">doubleunderline</span> - Make text 909double underlined (Alias: <code>doubleUnderline</code>)</li> 910<li><span style="border: 1px">framed</span> - Draw a frame around the text</li> 911</ul> 912<h5>Foreground colors<span><a class="mark" href="#util_foreground_colors" id="util_foreground_colors">#</a></span></h5> 913<ul> 914<li><code>black</code></li> 915<li><code>red</code></li> 916<li><code>green</code></li> 917<li><code>yellow</code></li> 918<li><code>blue</code></li> 919<li><code>magenta</code></li> 920<li><code>cyan</code></li> 921<li><code>white</code></li> 922<li><code>gray</code> (alias: <code>grey</code>, <code>blackBright</code>)</li> 923<li><code>redBright</code></li> 924<li><code>greenBright</code></li> 925<li><code>yellowBright</code></li> 926<li><code>blueBright</code></li> 927<li><code>magentaBright</code></li> 928<li><code>cyanBright</code></li> 929<li><code>whiteBright</code></li> 930</ul> 931<h5>Background colors<span><a class="mark" href="#util_background_colors" id="util_background_colors">#</a></span></h5> 932<ul> 933<li><code>bgBlack</code></li> 934<li><code>bgRed</code></li> 935<li><code>bgGreen</code></li> 936<li><code>bgYellow</code></li> 937<li><code>bgBlue</code></li> 938<li><code>bgMagenta</code></li> 939<li><code>bgCyan</code></li> 940<li><code>bgWhite</code></li> 941<li><code>bgGray</code> (alias: <code>bgGrey</code>, <code>bgBlackBright</code>)</li> 942<li><code>bgRedBright</code></li> 943<li><code>bgGreenBright</code></li> 944<li><code>bgYellowBright</code></li> 945<li><code>bgBlueBright</code></li> 946<li><code>bgMagentaBright</code></li> 947<li><code>bgCyanBright</code></li> 948<li><code>bgWhiteBright</code></li> 949</ul> 950<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> 951 952<p>Objects may also define their own 953<a href="#util_util_inspect_custom"><code>[util.inspect.custom](depth, opts)</code></a> function, 954which <code>util.inspect()</code> will invoke and use the result of when inspecting 955the object:</p> 956<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>); 957 958<span class="hljs-keyword">class</span> <span class="hljs-title class_">Box</span> { 959 <span class="hljs-title function_">constructor</span>(<span class="hljs-params">value</span>) { 960 <span class="hljs-variable language_">this</span>.<span class="hljs-property">value</span> = value; 961 } 962 963 [util.<span class="hljs-property">inspect</span>.<span class="hljs-property">custom</span>](depth, options) { 964 <span class="hljs-keyword">if</span> (depth < <span class="hljs-number">0</span>) { 965 <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>); 966 } 967 968 <span class="hljs-keyword">const</span> newOptions = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">assign</span>({}, options, { 969 <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> 970 }); 971 972 <span class="hljs-comment">// Five space padding because that's the size of "Box< ".</span> 973 <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>); 974 <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) 975 .<span class="hljs-title function_">replace</span>(<span class="hljs-regexp">/\n/g</span>, <span class="hljs-string">`\n<span class="hljs-subst">${padding}</span>`</span>); 976 <span class="hljs-keyword">return</span> <span class="hljs-string">`<span class="hljs-subst">${options.stylize(<span class="hljs-string">'Box'</span>, <span class="hljs-string">'special'</span>)}</span>< <span class="hljs-subst">${inner}</span> >`</span>; 977 } 978} 979 980<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>); 981 982util.<span class="hljs-title function_">inspect</span>(box); 983<span class="hljs-comment">// Returns: "Box< true >"</span></code></pre> 984<p>Custom <code>[util.inspect.custom](depth, opts)</code> functions typically return a string 985but may return a value of any type that will be formatted accordingly by 986<code>util.inspect()</code>.</p> 987<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>); 988 989<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> }; 990obj[util.<span class="hljs-property">inspect</span>.<span class="hljs-property">custom</span>] = <span class="hljs-function">(<span class="hljs-params">depth</span>) =></span> { 991 <span class="hljs-keyword">return</span> { <span class="hljs-attr">bar</span>: <span class="hljs-string">'baz'</span> }; 992}; 993 994util.<span class="hljs-title function_">inspect</span>(obj); 995<span class="hljs-comment">// Returns: "{ bar: 'baz' }"</span></code></pre> 996<h4><code>util.inspect.custom</code><span><a class="mark" href="#util_util_inspect_custom" id="util_util_inspect_custom">#</a></span></h4> 997<div class="api_metadata"> 998<details class="changelog"><summary>History</summary> 999<table> 1000<tbody><tr><th>Version</th><th>Changes</th></tr> 1001<tr><td>v10.12.0</td> 1002<td><p>This is now defined as a shared symbol.</p></td></tr> 1003<tr><td>v6.6.0</td> 1004<td><p><span>Added in: v6.6.0</span></p></td></tr> 1005</tbody></table> 1006</details> 1007</div> 1008<ul> 1009<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> 1010</ul> 1011<p>In addition to being accessible through <code>util.inspect.custom</code>, this 1012symbol is <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/for">registered globally</a> and can be 1013accessed in any environment as <code>Symbol.for('nodejs.util.inspect.custom')</code>.</p> 1014<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>); 1015 1016<span class="hljs-keyword">class</span> <span class="hljs-title class_">Password</span> { 1017 <span class="hljs-title function_">constructor</span>(<span class="hljs-params">value</span>) { 1018 <span class="hljs-variable language_">this</span>.<span class="hljs-property">value</span> = value; 1019 } 1020 1021 <span class="hljs-title function_">toString</span>(<span class="hljs-params"></span>) { 1022 <span class="hljs-keyword">return</span> <span class="hljs-string">'xxxxxxxx'</span>; 1023 } 1024 1025 [inspect]() { 1026 <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>; 1027 } 1028} 1029 1030<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>); 1031<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(password); 1032<span class="hljs-comment">// Prints Password <xxxxxxxx></span></code></pre> 1033<p>See <a href="#util_custom_inspection_functions_on_objects">Custom inspection functions on Objects</a> for more details.</p> 1034<h4><code>util.inspect.defaultOptions</code><span><a class="mark" href="#util_util_inspect_defaultoptions" id="util_util_inspect_defaultoptions">#</a></span></h4> 1035<div class="api_metadata"> 1036<span>Added in: v6.4.0</span> 1037</div> 1038<p>The <code>defaultOptions</code> value allows customization of the default options used by 1039<code>util.inspect</code>. This is useful for functions like <code>console.log</code> or 1040<code>util.format</code> which implicitly call into <code>util.inspect</code>. It shall be set to an 1041object containing one or more valid <a href="#util_util_inspect_object_options"><code>util.inspect()</code></a> options. Setting 1042option properties directly is also supported.</p> 1043<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>); 1044<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>); 1045 1046<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(arr); <span class="hljs-comment">// Logs the truncated array</span> 1047util.<span class="hljs-property">inspect</span>.<span class="hljs-property">defaultOptions</span>.<span class="hljs-property">maxArrayLength</span> = <span class="hljs-literal">null</span>; 1048<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> 1049</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> 1050<div class="api_metadata"> 1051<span>Added in: v9.0.0</span> 1052</div> 1053<ul> 1054<li><code>val1</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1055<li><code>val2</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1056<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1057</ul> 1058<p>Returns <code>true</code> if there is deep strict equality between <code>val1</code> and <code>val2</code>. 1059Otherwise, returns <code>false</code>.</p> 1060<p>See <a href="assert.html#assert_assert_deepstrictequal_actual_expected_message"><code>assert.deepStrictEqual()</code></a> for more information about deep strict 1061equality.</p> 1062</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> 1063<div class="api_metadata"> 1064<span>Added in: v8.0.0</span> 1065</div> 1066<ul> 1067<li><code>original</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1068<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1069</ul> 1070<p>Takes a function following the common error-first callback style, i.e. taking 1071an <code>(err, value) => ...</code> callback as the last argument, and returns a version 1072that returns promises.</p> 1073<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>); 1074<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'fs'</span>); 1075 1076<span class="hljs-keyword">const</span> stat = util.<span class="hljs-title function_">promisify</span>(fs.<span class="hljs-property">stat</span>); 1077<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> { 1078 <span class="hljs-comment">// Do something with `stats`</span> 1079}).<span class="hljs-title function_">catch</span>(<span class="hljs-function">(<span class="hljs-params">error</span>) =></span> { 1080 <span class="hljs-comment">// Handle the error.</span> 1081});</code></pre> 1082<p>Or, equivalently using <code>async function</code>s:</p> 1083<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>); 1084<span class="hljs-keyword">const</span> fs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'fs'</span>); 1085 1086<span class="hljs-keyword">const</span> stat = util.<span class="hljs-title function_">promisify</span>(fs.<span class="hljs-property">stat</span>); 1087 1088<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">callStat</span>(<span class="hljs-params"></span>) { 1089 <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>); 1090 <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>); 1091}</code></pre> 1092<p>If there is an <code>original[util.promisify.custom]</code> property present, <code>promisify</code> 1093will return its value, see <a href="#util_custom_promisified_functions">Custom promisified functions</a>.</p> 1094<p><code>promisify()</code> assumes that <code>original</code> is a function taking a callback as its 1095final argument in all cases. If <code>original</code> is not a function, <code>promisify()</code> 1096will throw an error. If <code>original</code> is a function but its last argument is not 1097an error-first callback, it will still be passed an error-first 1098callback as its last argument.</p> 1099<p>Using <code>promisify()</code> on class methods or other methods that use <code>this</code> may not 1100work as expected unless handled specially:</p> 1101<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>); 1102 1103<span class="hljs-keyword">class</span> <span class="hljs-title class_">Foo</span> { 1104 <span class="hljs-title function_">constructor</span>(<span class="hljs-params"></span>) { 1105 <span class="hljs-variable language_">this</span>.<span class="hljs-property">a</span> = <span class="hljs-number">42</span>; 1106 } 1107 1108 <span class="hljs-title function_">bar</span>(<span class="hljs-params">callback</span>) { 1109 <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>); 1110 } 1111} 1112 1113<span class="hljs-keyword">const</span> foo = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Foo</span>(); 1114 1115<span class="hljs-keyword">const</span> naiveBar = util.<span class="hljs-title function_">promisify</span>(foo.<span class="hljs-property">bar</span>); 1116<span class="hljs-comment">// TypeError: Cannot read property 'a' of undefined</span> 1117<span class="hljs-comment">// naiveBar().then(a => console.log(a));</span> 1118 1119naiveBar.<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> 1120 1121<span class="hljs-keyword">const</span> bindBar = naiveBar.<span class="hljs-title function_">bind</span>(foo); 1122<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> 1123<h4>Custom promisified functions<span><a class="mark" href="#util_custom_promisified_functions" id="util_custom_promisified_functions">#</a></span></h4> 1124<p>Using the <code>util.promisify.custom</code> symbol one can override the return value of 1125<a href="#util_util_promisify_original"><code>util.promisify()</code></a>:</p> 1126<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>); 1127 1128<span class="hljs-keyword">function</span> <span class="hljs-title function_">doSomething</span>(<span class="hljs-params">foo, callback</span>) { 1129 <span class="hljs-comment">// ...</span> 1130} 1131 1132doSomething[util.<span class="hljs-property">promisify</span>.<span class="hljs-property">custom</span>] = <span class="hljs-function">(<span class="hljs-params">foo</span>) =></span> { 1133 <span class="hljs-keyword">return</span> <span class="hljs-title function_">getPromiseSomehow</span>(); 1134}; 1135 1136<span class="hljs-keyword">const</span> promisified = util.<span class="hljs-title function_">promisify</span>(doSomething); 1137<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>]); 1138<span class="hljs-comment">// prints 'true'</span></code></pre> 1139<p>This can be useful for cases where the original function does not follow the 1140standard format of taking an error-first callback as the last argument.</p> 1141<p>For example, with a function that takes in 1142<code>(foo, onSuccessCallback, onErrorCallback)</code>:</p> 1143<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> { 1144 <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> { 1145 <span class="hljs-title function_">doSomething</span>(foo, resolve, reject); 1146 }); 1147};</code></pre> 1148<p>If <code>promisify.custom</code> is defined but is not a function, <code>promisify()</code> will 1149throw an error.</p> 1150<h4><code>util.promisify.custom</code><span><a class="mark" href="#util_util_promisify_custom" id="util_util_promisify_custom">#</a></span></h4> 1151<div class="api_metadata"> 1152<details class="changelog"><summary>History</summary> 1153<table> 1154<tbody><tr><th>Version</th><th>Changes</th></tr> 1155<tr><td>v13.12.0, v12.16.2</td> 1156<td><p>This is now defined as a shared symbol.</p></td></tr> 1157<tr><td>v8.0.0</td> 1158<td><p><span>Added in: v8.0.0</span></p></td></tr> 1159</tbody></table> 1160</details> 1161</div> 1162<ul> 1163<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, 1164see <a href="#util_custom_promisified_functions">Custom promisified functions</a>.</li> 1165</ul> 1166<p>In addition to being accessible through <code>util.promisify.custom</code>, this 1167symbol is <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/for">registered globally</a> and can be 1168accessed in any environment as <code>Symbol.for('nodejs.util.promisify.custom')</code>.</p> 1169<p>For example, with a function that takes in 1170<code>(foo, onSuccessCallback, onErrorCallback)</code>:</p> 1171<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>); 1172 1173doSomething[kCustomPromisifiedSymbol] = <span class="hljs-function">(<span class="hljs-params">foo</span>) =></span> { 1174 <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> { 1175 <span class="hljs-title function_">doSomething</span>(foo, resolve, reject); 1176 }); 1177};</code></pre> 1178</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> 1179<div class="api_metadata"> 1180<span>Added in: v8.3.0</span> 1181</div> 1182<p>An implementation of the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> <code>TextDecoder</code> API.</p> 1183<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>); 1184<span class="hljs-keyword">let</span> string = <span class="hljs-string">''</span>; 1185<span class="hljs-keyword">let</span> buffer; 1186<span class="hljs-keyword">while</span> (buffer = <span class="hljs-title function_">getNextChunkSomehow</span>()) { 1187 string += decoder.<span class="hljs-title function_">decode</span>(buffer, { <span class="hljs-attr">stream</span>: <span class="hljs-literal">true</span> }); 1188} 1189string += decoder.<span class="hljs-title function_">decode</span>(); <span class="hljs-comment">// end-of-stream</span></code></pre> 1190<h4>WHATWG supported encodings<span><a class="mark" href="#util_whatwg_supported_encodings" id="util_whatwg_supported_encodings">#</a></span></h4> 1191<p>Per the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a>, the encodings supported by the 1192<code>TextDecoder</code> API are outlined in the tables below. For each encoding, 1193one or more aliases may be used.</p> 1194<p>Different Node.js build configurations support different sets of encodings. 1195(see <a href="intl.html">Internationalization</a>)</p> 1196<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> 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 1342<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> 1343<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> 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365<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> 1366<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> 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384<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> 1385<p>The <code>'iso-8859-16'</code> encoding listed in the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> 1386is not supported.</p> 1387<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> 1388<div class="api_metadata"> 1389<details class="changelog"><summary>History</summary> 1390<table> 1391<tbody><tr><th>Version</th><th>Changes</th></tr> 1392<tr><td>v11.0.0</td> 1393<td><p>The class is now available on the global object.</p></td></tr> 1394<tr><td>v8.3.0</td> 1395<td><p><span>Added in: v8.3.0</span></p></td></tr> 1396</tbody></table> 1397</details> 1398</div> 1399<ul> 1400<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 1401supports. <strong>Default:</strong> <code>'utf-8'</code>.</li> 1402<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1403<ul> 1404<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. 1405This option is not supported when ICU is disabled 1406(see <a href="intl.html">Internationalization</a>). <strong>Default:</strong> <code>false</code>.</li> 1407<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 1408order mark in the decoded result. When <code>false</code>, the byte order mark will 1409be removed from the output. This option is only used when <code>encoding</code> is 1410<code>'utf-8'</code>, <code>'utf-16be'</code> or <code>'utf-16le'</code>. <strong>Default:</strong> <code>false</code>.</li> 1411</ul> 1412</li> 1413</ul> 1414<p>Creates an new <code>TextDecoder</code> instance. The <code>encoding</code> may specify one of the 1415supported encodings or an alias.</p> 1416<p>The <code>TextDecoder</code> class is also available on the global object.</p> 1417<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> 1418<ul> 1419<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 1420<code>TypedArray</code> instance containing the encoded data.</li> 1421<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1422<ul> 1423<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. 1424<strong>Default:</strong> <code>false</code>.</li> 1425</ul> 1426</li> 1427<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1428</ul> 1429<p>Decodes the <code>input</code> and returns a string. If <code>options.stream</code> is <code>true</code>, any 1430incomplete byte sequences occurring at the end of the <code>input</code> are buffered 1431internally and emitted after the next call to <code>textDecoder.decode()</code>.</p> 1432<p>If <code>textDecoder.fatal</code> is <code>true</code>, decoding errors that occur will result in a 1433<code>TypeError</code> being thrown.</p> 1434<h4><code>textDecoder.encoding</code><span><a class="mark" href="#util_textdecoder_encoding" id="util_textdecoder_encoding">#</a></span></h4> 1435<ul> 1436<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1437</ul> 1438<p>The encoding supported by the <code>TextDecoder</code> instance.</p> 1439<h4><code>textDecoder.fatal</code><span><a class="mark" href="#util_textdecoder_fatal" id="util_textdecoder_fatal">#</a></span></h4> 1440<ul> 1441<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1442</ul> 1443<p>The value will be <code>true</code> if decoding errors result in a <code>TypeError</code> being 1444thrown.</p> 1445<h4><code>textDecoder.ignoreBOM</code><span><a class="mark" href="#util_textdecoder_ignorebom" id="util_textdecoder_ignorebom">#</a></span></h4> 1446<ul> 1447<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1448</ul> 1449<p>The value will be <code>true</code> if the decoding result will include the byte order 1450mark.</p> 1451</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> 1452<div class="api_metadata"> 1453<details class="changelog"><summary>History</summary> 1454<table> 1455<tbody><tr><th>Version</th><th>Changes</th></tr> 1456<tr><td>v11.0.0</td> 1457<td><p>The class is now available on the global object.</p></td></tr> 1458<tr><td>v8.3.0</td> 1459<td><p><span>Added in: v8.3.0</span></p></td></tr> 1460</tbody></table> 1461</details> 1462</div> 1463<p>An implementation of the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> <code>TextEncoder</code> API. All 1464instances of <code>TextEncoder</code> only support UTF-8 encoding.</p> 1465<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>(); 1466<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> 1467<p>The <code>TextEncoder</code> class is also available on the global object.</p> 1468<h4><code>textEncoder.encode([input])</code><span><a class="mark" href="#util_textencoder_encode_input" id="util_textencoder_encode_input">#</a></span></h4> 1469<ul> 1470<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> 1471<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li> 1472</ul> 1473<p>UTF-8 encodes the <code>input</code> string and returns a <code>Uint8Array</code> containing the 1474encoded bytes.</p> 1475<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> 1476<ul> 1477<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> 1478<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> 1479<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1480<ul> 1481<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> 1482<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> 1483</ul> 1484</li> 1485</ul> 1486<p>UTF-8 encodes the <code>src</code> string to the <code>dest</code> Uint8Array and returns an object 1487containing the read Unicode code units and written UTF-8 bytes.</p> 1488<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>(); 1489<span class="hljs-keyword">const</span> src = <span class="hljs-string">'this is some data'</span>; 1490<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>); 1491<span class="hljs-keyword">const</span> { read, written } = encoder.<span class="hljs-title function_">encodeInto</span>(src, dest);</code></pre> 1492<h4><code>textEncoder.encoding</code><span><a class="mark" href="#util_textencoder_encoding" id="util_textencoder_encoding">#</a></span></h4> 1493<ul> 1494<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1495</ul> 1496<p>The encoding supported by the <code>TextEncoder</code> instance. Always set to <code>'utf-8'</code>.</p> 1497</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> 1498<div class="api_metadata"> 1499<span>Added in: v14.18.0</span> 1500</div> 1501<ul> 1502<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1503</ul> 1504<p>Returns the <code>string</code> after replacing any surrogate code points 1505(or equivalently, any unpaired surrogate code units) with the 1506Unicode "replacement character" U+FFFD.</p> 1507</section><section><h3><code>util.types</code><span><a class="mark" href="#util_util_types" id="util_util_types">#</a></span></h3> 1508<div class="api_metadata"> 1509<span>Added in: v10.0.0</span> 1510</div> 1511<p><code>util.types</code> provides type checks for different kinds of built-in objects. 1512Unlike <code>instanceof</code> or <code>Object.prototype.toString.call(value)</code>, these checks do 1513not inspect properties of the object that are accessible from JavaScript (like 1514their prototype), and usually have the overhead of calling into C++.</p> 1515<p>The result generally does not make any guarantees about what kinds of 1516properties or behavior a value exposes in JavaScript. They are primarily 1517useful for addon developers who prefer to do type checking in JavaScript.</p> 1518<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> 1519<div class="api_metadata"> 1520<span>Added in: v10.0.0</span> 1521</div> 1522<ul> 1523<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1524<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1525</ul> 1526<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 1527<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> instance.</p> 1528<p>See also <a href="#util_util_types_isarraybuffer_value"><code>util.types.isArrayBuffer()</code></a> and 1529<a href="#util_util_types_issharedarraybuffer_value"><code>util.types.isSharedArrayBuffer()</code></a>.</p> 1530<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> 1531util.<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> 1532<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> 1533<div class="api_metadata"> 1534<span>Added in: v10.0.0</span> 1535</div> 1536<ul> 1537<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1538<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1539</ul> 1540<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> 1541views, 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 1542<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/isView"><code>ArrayBuffer.isView()</code></a>.</p> 1543<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> 1544util.<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> 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_">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> 1546util.<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> 1547<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> 1548<div class="api_metadata"> 1549<span>Added in: v10.0.0</span> 1550</div> 1551<ul> 1552<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1553<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1554</ul> 1555<p>Returns <code>true</code> if the value is an <code>arguments</code> object.</p> 1556<!-- eslint-disable prefer-rest-params --> 1557<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) { 1558 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> 1559}</code></pre> 1560<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> 1561<div class="api_metadata"> 1562<span>Added in: v10.0.0</span> 1563</div> 1564<ul> 1565<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1566<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1567</ul> 1568<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. 1569This 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 1570desirable to test for both; See <a href="#util_util_types_isanyarraybuffer_value"><code>util.types.isAnyArrayBuffer()</code></a> for that.</p> 1571<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> 1572util.<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> 1573<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> 1574<div class="api_metadata"> 1575<span>Added in: v10.0.0</span> 1576</div> 1577<ul> 1578<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1579<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1580</ul> 1581<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>. 1582This only reports back what the JavaScript engine is seeing; 1583in particular, the return value may not match the original source code if 1584a transpilation tool was used.</p> 1585<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> 1586util.<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> 1587<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> 1588<div class="api_metadata"> 1589<span>Added in: v10.0.0</span> 1590</div> 1591<ul> 1592<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1593<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1594</ul> 1595<p>Returns <code>true</code> if the value is a <code>BigInt64Array</code> instance.</p> 1596<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> 1597util.<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> 1598<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> 1599<div class="api_metadata"> 1600<span>Added in: v10.0.0</span> 1601</div> 1602<ul> 1603<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1604<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1605</ul> 1606<p>Returns <code>true</code> if the value is a <code>BigUint64Array</code> instance.</p> 1607<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> 1608util.<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> 1609<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> 1610<div class="api_metadata"> 1611<span>Added in: v10.0.0</span> 1612</div> 1613<ul> 1614<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1615<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1616</ul> 1617<p>Returns <code>true</code> if the value is a boolean object, e.g. created 1618by <code>new Boolean()</code>.</p> 1619<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> 1620util.<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> 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">false</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-keyword">new</span> <span class="hljs-title class_">Boolean</span>(<span class="hljs-literal">true</span>)); <span class="hljs-comment">// Returns true</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">false</span>)); <span class="hljs-comment">// Returns false</span> 1624util.<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> 1625<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> 1626<div class="api_metadata"> 1627<span>Added in: v10.11.0</span> 1628</div> 1629<ul> 1630<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1631<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1632</ul> 1633<p>Returns <code>true</code> if the value is any boxed primitive object, e.g. created 1634by <code>new Boolean()</code>, <code>new String()</code> or <code>Object(Symbol())</code>.</p> 1635<p>For example:</p> 1636<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> 1637util.<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> 1638util.<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> 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_">Symbol</span>(<span class="hljs-string">'foo'</span>))); <span class="hljs-comment">// Returns true</span> 1640util.<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> 1641<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> 1642<div class="api_metadata"> 1643<span>Added in: v10.0.0</span> 1644</div> 1645<ul> 1646<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1647<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1648</ul> 1649<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> 1650<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>); 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_">DataView</span>(ab)); <span class="hljs-comment">// Returns true</span> 1652util.<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> 1653<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> 1654<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> 1655<div class="api_metadata"> 1656<span>Added in: v10.0.0</span> 1657</div> 1658<ul> 1659<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1660<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1661</ul> 1662<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> 1663<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> 1664<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> 1665<div class="api_metadata"> 1666<span>Added in: v10.0.0</span> 1667</div> 1668<ul> 1669<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1670<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1671</ul> 1672<p>Returns <code>true</code> if the value is a native <code>External</code> value.</p> 1673<p>A native <code>External</code> value is a special type of object that contains a 1674raw C++ pointer (<code>void*</code>) for access from native code, and has no other 1675properties. Such objects are created either by Node.js internals or native 1676addons. 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 1677<code>null</code> prototype.</p> 1678<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> 1679<span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string"><stdlib.h></span></span> 1680napi_value result; 1681<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> { 1682 <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>); 1683 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); 1684 <span class="hljs-keyword">if</span> (status != napi_ok) { 1685 napi_throw_error(env, <span class="hljs-literal">NULL</span>, <span class="hljs-string">"napi_create_external failed"</span>); 1686 <span class="hljs-keyword">return</span> <span class="hljs-literal">NULL</span>; 1687 } 1688 <span class="hljs-keyword">return</span> result; 1689} 1690... 1691DECLARE_NAPI_PROPERTY(<span class="hljs-string">"myNapi"</span>, MyNapi) 1692...</code></pre> 1693<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>); 1694<span class="hljs-keyword">const</span> data = native.<span class="hljs-title function_">myNapi</span>(); 1695util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isExternal</span>(data); <span class="hljs-comment">// returns true</span> 1696util.<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> 1697util.<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> 1698<p>For further information on <code>napi_create_external</code>, refer to 1699<a href="n-api.html#n_api_napi_create_external"><code>napi_create_external()</code></a>.</p> 1700<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> 1701<div class="api_metadata"> 1702<span>Added in: v10.0.0</span> 1703</div> 1704<ul> 1705<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1706<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1707</ul> 1708<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> 1709<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> 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>32<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1711util.<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> 1712<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> 1713<div class="api_metadata"> 1714<span>Added in: v10.0.0</span> 1715</div> 1716<ul> 1717<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1718<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1719</ul> 1720<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> 1721<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> 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_">Uint</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns false</span> 1723util.<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> 1724<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> 1725<div class="api_metadata"> 1726<span>Added in: v10.0.0</span> 1727</div> 1728<ul> 1729<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1730<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1731</ul> 1732<p>Returns <code>true</code> if the value is a generator function. 1733This only reports back what the JavaScript engine is seeing; 1734in particular, the return value may not match the original source code if 1735a transpilation tool was used.</p> 1736<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> 1737util.<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> 1738<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> 1739<div class="api_metadata"> 1740<span>Added in: v10.0.0</span> 1741</div> 1742<ul> 1743<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1744<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1745</ul> 1746<p>Returns <code>true</code> if the value is a generator object as returned from a 1747built-in generator function. 1748This only reports back what the JavaScript engine is seeing; 1749in particular, the return value may not match the original source code if 1750a transpilation tool was used.</p> 1751<pre><code class="language-js"><span class="hljs-keyword">function</span>* <span class="hljs-title function_">foo</span>(<span class="hljs-params"></span>) {} 1752<span class="hljs-keyword">const</span> generator = <span class="hljs-title function_">foo</span>(); 1753util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isGeneratorObject</span>(generator); <span class="hljs-comment">// Returns true</span></code></pre> 1754<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> 1755<div class="api_metadata"> 1756<span>Added in: v10.0.0</span> 1757</div> 1758<ul> 1759<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1760<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1761</ul> 1762<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> 1763<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> 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_">Int</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1765util.<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> 1766<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> 1767<div class="api_metadata"> 1768<span>Added in: v10.0.0</span> 1769</div> 1770<ul> 1771<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1772<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1773</ul> 1774<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> 1775<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> 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_">Int</span>16<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1777util.<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> 1778<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> 1779<div class="api_metadata"> 1780<span>Added in: v10.0.0</span> 1781</div> 1782<ul> 1783<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1784<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1785</ul> 1786<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> 1787<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> 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_">Int</span>32<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1789util.<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> 1790<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> 1791<div class="api_metadata"> 1792<span>Added in: v10.0.0</span> 1793</div> 1794<ul> 1795<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1796<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1797</ul> 1798<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> 1799<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> 1800<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> 1801<div class="api_metadata"> 1802<span>Added in: v10.0.0</span> 1803</div> 1804<ul> 1805<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1806<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1807</ul> 1808<p>Returns <code>true</code> if the value is an iterator returned for a built-in 1809<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map"><code>Map</code></a> instance.</p> 1810<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>(); 1811util.<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> 1812util.<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> 1813util.<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> 1814util.<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> 1815<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> 1816<div class="api_metadata"> 1817<span>Added in: v10.0.0</span> 1818</div> 1819<ul> 1820<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1821<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1822</ul> 1823<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> 1824<!-- eslint-skip --> 1825<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>; 1826 1827util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isModuleNamespaceObject</span>(ns); <span class="hljs-comment">// Returns true</span></code></pre> 1828<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> 1829<div class="api_metadata"> 1830<span>Added in: v10.0.0</span> 1831</div> 1832<ul> 1833<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1834<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1835</ul> 1836<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> 1837<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> 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_">TypeError</span>()); <span class="hljs-comment">// Returns true</span> 1839util.<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> 1840<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> 1841<div class="api_metadata"> 1842<span>Added in: v10.0.0</span> 1843</div> 1844<ul> 1845<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1846<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1847</ul> 1848<p>Returns <code>true</code> if the value is a number object, e.g. created 1849by <code>new Number()</code>.</p> 1850<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> 1851util.<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> 1852<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> 1853<div class="api_metadata"> 1854<span>Added in: v10.0.0</span> 1855</div> 1856<ul> 1857<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1858<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1859</ul> 1860<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> 1861<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> 1862<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> 1863<div class="api_metadata"> 1864<span>Added in: v10.0.0</span> 1865</div> 1866<ul> 1867<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1868<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1869</ul> 1870<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> 1871<pre><code class="language-js"><span class="hljs-keyword">const</span> target = {}; 1872<span class="hljs-keyword">const</span> proxy = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Proxy</span>(target, {}); 1873util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isProxy</span>(target); <span class="hljs-comment">// Returns false</span> 1874util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isProxy</span>(proxy); <span class="hljs-comment">// Returns true</span></code></pre> 1875<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> 1876<div class="api_metadata"> 1877<span>Added in: v10.0.0</span> 1878</div> 1879<ul> 1880<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1881<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1882</ul> 1883<p>Returns <code>true</code> if the value is a regular expression object.</p> 1884<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> 1885util.<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> 1886<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> 1887<div class="api_metadata"> 1888<span>Added in: v10.0.0</span> 1889</div> 1890<ul> 1891<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1892<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1893</ul> 1894<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> 1895<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> 1896<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> 1897<div class="api_metadata"> 1898<span>Added in: v10.0.0</span> 1899</div> 1900<ul> 1901<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1902<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1903</ul> 1904<p>Returns <code>true</code> if the value is an iterator returned for a built-in 1905<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set"><code>Set</code></a> instance.</p> 1906<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>(); 1907util.<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> 1908util.<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> 1909util.<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> 1910util.<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> 1911<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> 1912<div class="api_metadata"> 1913<span>Added in: v10.0.0</span> 1914</div> 1915<ul> 1916<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1917<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1918</ul> 1919<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. 1920This 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 1921desirable to test for both; See <a href="#util_util_types_isanyarraybuffer_value"><code>util.types.isAnyArrayBuffer()</code></a> for that.</p> 1922<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> 1923util.<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> 1924<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> 1925<div class="api_metadata"> 1926<span>Added in: v10.0.0</span> 1927</div> 1928<ul> 1929<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1930<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1931</ul> 1932<p>Returns <code>true</code> if the value is a string object, e.g. created 1933by <code>new String()</code>.</p> 1934<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> 1935util.<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> 1936<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> 1937<div class="api_metadata"> 1938<span>Added in: v10.0.0</span> 1939</div> 1940<ul> 1941<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1942<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1943</ul> 1944<p>Returns <code>true</code> if the value is a symbol object, created 1945by calling <code>Object()</code> on a <code>Symbol</code> primitive.</p> 1946<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>); 1947util.<span class="hljs-property">types</span>.<span class="hljs-title function_">isSymbolObject</span>(symbol); <span class="hljs-comment">// Returns false</span> 1948util.<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> 1949<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> 1950<div class="api_metadata"> 1951<span>Added in: v10.0.0</span> 1952</div> 1953<ul> 1954<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1955<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1956</ul> 1957<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> 1958<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> 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_">Uint</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1960util.<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> 1961<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> 1962<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> 1963<div class="api_metadata"> 1964<span>Added in: v10.0.0</span> 1965</div> 1966<ul> 1967<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1968<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1969</ul> 1970<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> 1971<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> 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_">Uint</span>8<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1973util.<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> 1974<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> 1975<div class="api_metadata"> 1976<span>Added in: v10.0.0</span> 1977</div> 1978<ul> 1979<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1980<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1981</ul> 1982<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> 1983<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> 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_">Uint</span>8ClampedArray()); <span class="hljs-comment">// Returns true</span> 1985util.<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> 1986<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> 1987<div class="api_metadata"> 1988<span>Added in: v10.0.0</span> 1989</div> 1990<ul> 1991<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1992<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1993</ul> 1994<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> 1995<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> 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_">Uint</span>16<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 1997util.<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> 1998<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> 1999<div class="api_metadata"> 2000<span>Added in: v10.0.0</span> 2001</div> 2002<ul> 2003<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2004<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2005</ul> 2006<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> 2007<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> 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_">Uint</span>32<span class="hljs-built_in">Array</span>()); <span class="hljs-comment">// Returns true</span> 2009util.<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> 2010<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> 2011<div class="api_metadata"> 2012<span>Added in: v10.0.0</span> 2013</div> 2014<ul> 2015<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2016<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2017</ul> 2018<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> 2019<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> 2020<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> 2021<div class="api_metadata"> 2022<span>Added in: v10.0.0</span> 2023</div> 2024<ul> 2025<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2026<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2027</ul> 2028<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> 2029<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> 2030<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> 2031<div class="api_metadata"> 2032<span>Added in: v10.0.0</span><span>Deprecated since: v14.0.0</span> 2033</div> 2034<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> 2035<ul> 2036<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2037<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2038</ul> 2039<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> 2040<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); 2041util.<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> 2042</section><section><h3>Deprecated APIs<span><a class="mark" href="#util_deprecated_apis" id="util_deprecated_apis">#</a></span></h3> 2043<p>The following APIs are deprecated and should no longer be used. Existing 2044applications and modules should be updated to find alternative approaches.</p> 2045<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> 2046<div class="api_metadata"> 2047<span>Added in: v0.7.5</span><span>Deprecated since: v6.0.0</span> 2048</div> 2049<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> 2050<ul> 2051<li><code>target</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2052<li><code>source</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 2053</ul> 2054<p>The <code>util._extend()</code> method was never intended to be used outside of internal 2055Node.js modules. The community found and used it anyway.</p> 2056<p>It is deprecated and should not be used in new code. JavaScript comes with very 2057similar 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> 2058<h4><code>util.isArray(object)</code><span><a class="mark" href="#util_util_isarray_object" id="util_util_isarray_object">#</a></span></h4> 2059<div class="api_metadata"> 2060<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2061</div> 2062<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> 2063<ul> 2064<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2065<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2066</ul> 2067<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> 2068<p>Returns <code>true</code> if the given <code>object</code> is an <code>Array</code>. Otherwise, returns <code>false</code>.</p> 2069<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>); 2070 2071util.<span class="hljs-title function_">isArray</span>([]); 2072<span class="hljs-comment">// Returns: true</span> 2073util.<span class="hljs-title function_">isArray</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Array</span>()); 2074<span class="hljs-comment">// Returns: true</span> 2075util.<span class="hljs-title function_">isArray</span>({}); 2076<span class="hljs-comment">// Returns: false</span></code></pre> 2077<h4><code>util.isBoolean(object)</code><span><a class="mark" href="#util_util_isboolean_object" id="util_util_isboolean_object">#</a></span></h4> 2078<div class="api_metadata"> 2079<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2080</div> 2081<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> 2082<ul> 2083<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2084<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2085</ul> 2086<p>Returns <code>true</code> if the given <code>object</code> is a <code>Boolean</code>. Otherwise, returns <code>false</code>.</p> 2087<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>); 2088 2089util.<span class="hljs-title function_">isBoolean</span>(<span class="hljs-number">1</span>); 2090<span class="hljs-comment">// Returns: false</span> 2091util.<span class="hljs-title function_">isBoolean</span>(<span class="hljs-number">0</span>); 2092<span class="hljs-comment">// Returns: false</span> 2093util.<span class="hljs-title function_">isBoolean</span>(<span class="hljs-literal">false</span>); 2094<span class="hljs-comment">// Returns: true</span></code></pre> 2095<h4><code>util.isBuffer(object)</code><span><a class="mark" href="#util_util_isbuffer_object" id="util_util_isbuffer_object">#</a></span></h4> 2096<div class="api_metadata"> 2097<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2098</div> 2099<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> 2100<ul> 2101<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2102<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2103</ul> 2104<p>Returns <code>true</code> if the given <code>object</code> is a <code>Buffer</code>. Otherwise, returns <code>false</code>.</p> 2105<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>); 2106 2107util.<span class="hljs-title function_">isBuffer</span>({ <span class="hljs-attr">length</span>: <span class="hljs-number">0</span> }); 2108<span class="hljs-comment">// Returns: false</span> 2109util.<span class="hljs-title function_">isBuffer</span>([]); 2110<span class="hljs-comment">// Returns: false</span> 2111util.<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>)); 2112<span class="hljs-comment">// Returns: true</span></code></pre> 2113<h4><code>util.isDate(object)</code><span><a class="mark" href="#util_util_isdate_object" id="util_util_isdate_object">#</a></span></h4> 2114<div class="api_metadata"> 2115<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2116</div> 2117<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> 2118<ul> 2119<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2120<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2121</ul> 2122<p>Returns <code>true</code> if the given <code>object</code> is a <code>Date</code>. Otherwise, returns <code>false</code>.</p> 2123<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>); 2124 2125util.<span class="hljs-title function_">isDate</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>()); 2126<span class="hljs-comment">// Returns: true</span> 2127util.<span class="hljs-title function_">isDate</span>(<span class="hljs-title class_">Date</span>()); 2128<span class="hljs-comment">// false (without 'new' returns a String)</span> 2129util.<span class="hljs-title function_">isDate</span>({}); 2130<span class="hljs-comment">// Returns: false</span></code></pre> 2131<h4><code>util.isError(object)</code><span><a class="mark" href="#util_util_iserror_object" id="util_util_iserror_object">#</a></span></h4> 2132<div class="api_metadata"> 2133<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2134</div> 2135<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> 2136<ul> 2137<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2138<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2139</ul> 2140<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 2141<code>false</code>.</p> 2142<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>); 2143 2144util.<span class="hljs-title function_">isError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>()); 2145<span class="hljs-comment">// Returns: true</span> 2146util.<span class="hljs-title function_">isError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>()); 2147<span class="hljs-comment">// Returns: true</span> 2148util.<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> }); 2149<span class="hljs-comment">// Returns: false</span></code></pre> 2150<p>This method relies on <code>Object.prototype.toString()</code> behavior. It is 2151possible to obtain an incorrect result when the <code>object</code> argument manipulates 2152<code>@@toStringTag</code>.</p> 2153<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>); 2154<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> }; 2155 2156util.<span class="hljs-title function_">isError</span>(obj); 2157<span class="hljs-comment">// Returns: false</span> 2158obj[<span class="hljs-title class_">Symbol</span>.<span class="hljs-property">toStringTag</span>] = <span class="hljs-string">'Error'</span>; 2159util.<span class="hljs-title function_">isError</span>(obj); 2160<span class="hljs-comment">// Returns: true</span></code></pre> 2161<h4><code>util.isFunction(object)</code><span><a class="mark" href="#util_util_isfunction_object" id="util_util_isfunction_object">#</a></span></h4> 2162<div class="api_metadata"> 2163<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2164</div> 2165<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> 2166<ul> 2167<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2168<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2169</ul> 2170<p>Returns <code>true</code> if the given <code>object</code> is a <code>Function</code>. Otherwise, returns 2171<code>false</code>.</p> 2172<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>); 2173 2174<span class="hljs-keyword">function</span> <span class="hljs-title function_">Foo</span>(<span class="hljs-params"></span>) {} 2175<span class="hljs-keyword">const</span> <span class="hljs-title function_">Bar</span> = (<span class="hljs-params"></span>) => {}; 2176 2177util.<span class="hljs-title function_">isFunction</span>({}); 2178<span class="hljs-comment">// Returns: false</span> 2179util.<span class="hljs-title function_">isFunction</span>(<span class="hljs-title class_">Foo</span>); 2180<span class="hljs-comment">// Returns: true</span> 2181util.<span class="hljs-title function_">isFunction</span>(<span class="hljs-title class_">Bar</span>); 2182<span class="hljs-comment">// Returns: true</span></code></pre> 2183<h4><code>util.isNull(object)</code><span><a class="mark" href="#util_util_isnull_object" id="util_util_isnull_object">#</a></span></h4> 2184<div class="api_metadata"> 2185<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2186</div> 2187<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> 2188<ul> 2189<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2190<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2191</ul> 2192<p>Returns <code>true</code> if the given <code>object</code> is strictly <code>null</code>. Otherwise, returns 2193<code>false</code>.</p> 2194<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>); 2195 2196util.<span class="hljs-title function_">isNull</span>(<span class="hljs-number">0</span>); 2197<span class="hljs-comment">// Returns: false</span> 2198util.<span class="hljs-title function_">isNull</span>(<span class="hljs-literal">undefined</span>); 2199<span class="hljs-comment">// Returns: false</span> 2200util.<span class="hljs-title function_">isNull</span>(<span class="hljs-literal">null</span>); 2201<span class="hljs-comment">// Returns: true</span></code></pre> 2202<h4><code>util.isNullOrUndefined(object)</code><span><a class="mark" href="#util_util_isnullorundefined_object" id="util_util_isnullorundefined_object">#</a></span></h4> 2203<div class="api_metadata"> 2204<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2205</div> 2206<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use 2207<code>value === undefined || value === null</code> instead.</div><p></p> 2208<ul> 2209<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2210<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2211</ul> 2212<p>Returns <code>true</code> if the given <code>object</code> is <code>null</code> or <code>undefined</code>. Otherwise, 2213returns <code>false</code>.</p> 2214<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>); 2215 2216util.<span class="hljs-title function_">isNullOrUndefined</span>(<span class="hljs-number">0</span>); 2217<span class="hljs-comment">// Returns: false</span> 2218util.<span class="hljs-title function_">isNullOrUndefined</span>(<span class="hljs-literal">undefined</span>); 2219<span class="hljs-comment">// Returns: true</span> 2220util.<span class="hljs-title function_">isNullOrUndefined</span>(<span class="hljs-literal">null</span>); 2221<span class="hljs-comment">// Returns: true</span></code></pre> 2222<h4><code>util.isNumber(object)</code><span><a class="mark" href="#util_util_isnumber_object" id="util_util_isnumber_object">#</a></span></h4> 2223<div class="api_metadata"> 2224<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2225</div> 2226<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> 2227<ul> 2228<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2229<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2230</ul> 2231<p>Returns <code>true</code> if the given <code>object</code> is a <code>Number</code>. Otherwise, returns <code>false</code>.</p> 2232<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>); 2233 2234util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-literal">false</span>); 2235<span class="hljs-comment">// Returns: false</span> 2236util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-title class_">Infinity</span>); 2237<span class="hljs-comment">// Returns: true</span> 2238util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-number">0</span>); 2239<span class="hljs-comment">// Returns: true</span> 2240util.<span class="hljs-title function_">isNumber</span>(<span class="hljs-title class_">Na</span>N); 2241<span class="hljs-comment">// Returns: true</span></code></pre> 2242<h4><code>util.isObject(object)</code><span><a class="mark" href="#util_util_isobject_object" id="util_util_isobject_object">#</a></span></h4> 2243<div class="api_metadata"> 2244<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2245</div> 2246<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: 2247Use <code>value !== null && typeof value === 'object'</code> instead.</div><p></p> 2248<ul> 2249<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2250<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2251</ul> 2252<p>Returns <code>true</code> if the given <code>object</code> is strictly an <code>Object</code> <strong>and</strong> not a 2253<code>Function</code> (even though functions are objects in JavaScript). 2254Otherwise, returns <code>false</code>.</p> 2255<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>); 2256 2257util.<span class="hljs-title function_">isObject</span>(<span class="hljs-number">5</span>); 2258<span class="hljs-comment">// Returns: false</span> 2259util.<span class="hljs-title function_">isObject</span>(<span class="hljs-literal">null</span>); 2260<span class="hljs-comment">// Returns: false</span> 2261util.<span class="hljs-title function_">isObject</span>({}); 2262<span class="hljs-comment">// Returns: true</span> 2263util.<span class="hljs-title function_">isObject</span>(<span class="hljs-function">() =></span> {}); 2264<span class="hljs-comment">// Returns: false</span></code></pre> 2265<h4><code>util.isPrimitive(object)</code><span><a class="mark" href="#util_util_isprimitive_object" id="util_util_isprimitive_object">#</a></span></h4> 2266<div class="api_metadata"> 2267<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2268</div> 2269<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use 2270<code>(typeof value !== 'object' && typeof value !== 'function') || value === null</code> 2271instead.</div><p></p> 2272<ul> 2273<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2274<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2275</ul> 2276<p>Returns <code>true</code> if the given <code>object</code> is a primitive type. Otherwise, returns 2277<code>false</code>.</p> 2278<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>); 2279 2280util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-number">5</span>); 2281<span class="hljs-comment">// Returns: true</span> 2282util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-string">'foo'</span>); 2283<span class="hljs-comment">// Returns: true</span> 2284util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-literal">false</span>); 2285<span class="hljs-comment">// Returns: true</span> 2286util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-literal">null</span>); 2287<span class="hljs-comment">// Returns: true</span> 2288util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-literal">undefined</span>); 2289<span class="hljs-comment">// Returns: true</span> 2290util.<span class="hljs-title function_">isPrimitive</span>({}); 2291<span class="hljs-comment">// Returns: false</span> 2292util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-function">() =></span> {}); 2293<span class="hljs-comment">// Returns: false</span> 2294util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-regexp">/^$/</span>); 2295<span class="hljs-comment">// Returns: false</span> 2296util.<span class="hljs-title function_">isPrimitive</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>()); 2297<span class="hljs-comment">// Returns: false</span></code></pre> 2298<h4><code>util.isRegExp(object)</code><span><a class="mark" href="#util_util_isregexp_object" id="util_util_isregexp_object">#</a></span></h4> 2299<div class="api_metadata"> 2300<span>Added in: v0.6.0</span><span>Deprecated since: v4.0.0</span> 2301</div> 2302<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated</div><p></p> 2303<ul> 2304<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2305<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2306</ul> 2307<p>Returns <code>true</code> if the given <code>object</code> is a <code>RegExp</code>. Otherwise, returns <code>false</code>.</p> 2308<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>); 2309 2310util.<span class="hljs-title function_">isRegExp</span>(<span class="hljs-regexp">/some regexp/</span>); 2311<span class="hljs-comment">// Returns: true</span> 2312util.<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>)); 2313<span class="hljs-comment">// Returns: true</span> 2314util.<span class="hljs-title function_">isRegExp</span>({}); 2315<span class="hljs-comment">// Returns: false</span></code></pre> 2316<h4><code>util.isString(object)</code><span><a class="mark" href="#util_util_isstring_object" id="util_util_isstring_object">#</a></span></h4> 2317<div class="api_metadata"> 2318<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2319</div> 2320<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> 2321<ul> 2322<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2323<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2324</ul> 2325<p>Returns <code>true</code> if the given <code>object</code> is a <code>string</code>. Otherwise, returns <code>false</code>.</p> 2326<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>); 2327 2328util.<span class="hljs-title function_">isString</span>(<span class="hljs-string">''</span>); 2329<span class="hljs-comment">// Returns: true</span> 2330util.<span class="hljs-title function_">isString</span>(<span class="hljs-string">'foo'</span>); 2331<span class="hljs-comment">// Returns: true</span> 2332util.<span class="hljs-title function_">isString</span>(<span class="hljs-title class_">String</span>(<span class="hljs-string">'foo'</span>)); 2333<span class="hljs-comment">// Returns: true</span> 2334util.<span class="hljs-title function_">isString</span>(<span class="hljs-number">5</span>); 2335<span class="hljs-comment">// Returns: false</span></code></pre> 2336<h4><code>util.isSymbol(object)</code><span><a class="mark" href="#util_util_issymbol_object" id="util_util_issymbol_object">#</a></span></h4> 2337<div class="api_metadata"> 2338<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2339</div> 2340<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> 2341<ul> 2342<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2343<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2344</ul> 2345<p>Returns <code>true</code> if the given <code>object</code> is a <code>Symbol</code>. Otherwise, returns <code>false</code>.</p> 2346<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>); 2347 2348util.<span class="hljs-title function_">isSymbol</span>(<span class="hljs-number">5</span>); 2349<span class="hljs-comment">// Returns: false</span> 2350util.<span class="hljs-title function_">isSymbol</span>(<span class="hljs-string">'foo'</span>); 2351<span class="hljs-comment">// Returns: false</span> 2352util.<span class="hljs-title function_">isSymbol</span>(<span class="hljs-title class_">Symbol</span>(<span class="hljs-string">'foo'</span>)); 2353<span class="hljs-comment">// Returns: true</span></code></pre> 2354<h4><code>util.isUndefined(object)</code><span><a class="mark" href="#util_util_isundefined_object" id="util_util_isundefined_object">#</a></span></h4> 2355<div class="api_metadata"> 2356<span>Added in: v0.11.5</span><span>Deprecated since: v4.0.0</span> 2357</div> 2358<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> 2359<ul> 2360<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2361<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 2362</ul> 2363<p>Returns <code>true</code> if the given <code>object</code> is <code>undefined</code>. Otherwise, returns <code>false</code>.</p> 2364<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>); 2365 2366<span class="hljs-keyword">const</span> foo = <span class="hljs-literal">undefined</span>; 2367util.<span class="hljs-title function_">isUndefined</span>(<span class="hljs-number">5</span>); 2368<span class="hljs-comment">// Returns: false</span> 2369util.<span class="hljs-title function_">isUndefined</span>(foo); 2370<span class="hljs-comment">// Returns: true</span> 2371util.<span class="hljs-title function_">isUndefined</span>(<span class="hljs-literal">null</span>); 2372<span class="hljs-comment">// Returns: false</span></code></pre> 2373<h4><code>util.log(string)</code><span><a class="mark" href="#util_util_log_string" id="util_util_log_string">#</a></span></h4> 2374<div class="api_metadata"> 2375<span>Added in: v0.3.0</span><span>Deprecated since: v6.0.0</span> 2376</div> 2377<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> 2378<ul> 2379<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2380</ul> 2381<p>The <code>util.log()</code> method prints the given <code>string</code> to <code>stdout</code> with an included 2382timestamp.</p> 2383<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>); 2384 2385util.<span class="hljs-title function_">log</span>(<span class="hljs-string">'Timestamped message.'</span>);</code></pre></section> 2386 <!-- API END --> 2387 </div> 2388 </div> 2389 </div> 2390 <script> 2391 'use strict'; 2392 { 2393 const kCustomPreference = 'customDarkTheme'; 2394 const userSettings = sessionStorage.getItem(kCustomPreference); 2395 const themeToggleButton = document.getElementById('theme-toggle-btn'); 2396 if (userSettings === null && window.matchMedia) { 2397 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 2398 if ('onchange' in mq) { 2399 function mqChangeListener(e) { 2400 document.body.classList.toggle('dark-mode', e.matches); 2401 } 2402 mq.addEventListener('change', mqChangeListener); 2403 if (themeToggleButton) { 2404 themeToggleButton.addEventListener('click', function() { 2405 mq.removeEventListener('change', mqChangeListener); 2406 }, { once: true }); 2407 } 2408 } 2409 if (mq.matches) { 2410 document.body.classList.add('dark-mode'); 2411 } 2412 } else if (userSettings === 'true') { 2413 document.body.classList.add('dark-mode'); 2414 } 2415 if (themeToggleButton) { 2416 themeToggleButton.hidden = false; 2417 themeToggleButton.addEventListener('click', function() { 2418 sessionStorage.setItem( 2419 kCustomPreference, 2420 document.body.classList.toggle('dark-mode') 2421 ); 2422 }); 2423 } 2424 } 2425 </script> 2426</body> 2427</html> 2428