1<!DOCTYPE html> 2<html lang="en"> 3<head> 4 <meta charset="utf-8"> 5 <meta name="viewport" content="width=device-width"> 6 <meta name="nodejs.org:node-version" content="v14.20.1"> 7 <title>VM (executing JavaScript) | Node.js v14.20.1 Documentation</title> 8 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> 9 <link rel="stylesheet" href="assets/style.css"> 10 <link rel="stylesheet" href="assets/hljs.css"> 11 <link rel="canonical" href="https://nodejs.org/api/vm.html"> 12</head> 13<body class="alt apidoc" id="api-section-vm"> 14 <div id="content" class="clearfix"> 15 <div id="column2" class="interior"> 16 <div id="intro" class="interior"> 17 <a href="/" title="Go back to the home page"> 18 Node.js 19 </a> 20 </div> 21 <ul> 22<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 23<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 24</ul> 25<hr class="line"> 26<ul> 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data-id="vm" class="interior"> 90 <header> 91 <div class="header-container"> 92 <h1>Node.js v14.20.1 documentation</h1> 93 <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 94 <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 95 <path fill="none" d="M0 0h24v24H0z" /> 96 <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 97 <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 98 </svg> 99 <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 100 <path d="M0 0h24v24H0z" fill="none" /> 101 <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 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href="https://nodejs.org/docs/latest-v14.x/api/vm.html">14.x <b>LTS</b></a></li> 124<li><a href="https://nodejs.org/docs/latest-v13.x/api/vm.html">13.x</a></li> 125<li><a href="https://nodejs.org/docs/latest-v12.x/api/vm.html">12.x <b>LTS</b></a></li> 126<li><a href="https://nodejs.org/docs/latest-v11.x/api/vm.html">11.x</a></li> 127<li><a href="https://nodejs.org/docs/latest-v10.x/api/vm.html">10.x</a></li> 128<li><a href="https://nodejs.org/docs/latest-v9.x/api/vm.html">9.x</a></li> 129<li><a href="https://nodejs.org/docs/latest-v8.x/api/vm.html">8.x</a></li> 130<li><a href="https://nodejs.org/docs/latest-v7.x/api/vm.html">7.x</a></li> 131<li><a href="https://nodejs.org/docs/latest-v6.x/api/vm.html">6.x</a></li> 132<li><a href="https://nodejs.org/docs/latest-v5.x/api/vm.html">5.x</a></li> 133<li><a href="https://nodejs.org/docs/latest-v4.x/api/vm.html">4.x</a></li> 134<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/vm.html">0.12.x</a></li> 135<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/vm.html">0.10.x</a></li></ol> 136 </li> 137 138 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/vm.md">Edit on GitHub</a></li> 139 </ul> 140 </div> 141 <hr> 142 </header> 143 144 <details id="toc" open><summary>Table of contents</summary><ul> 145<li><span class="stability_2"><a href="#vm_vm_executing_javascript">VM (executing JavaScript)</a></span> 146<ul> 147<li><a href="#vm_class_vm_script">Class: <code>vm.Script</code></a> 148<ul> 149<li><a href="#vm_new_vm_script_code_options"><code>new vm.Script(code[, options])</code></a></li> 150<li><a href="#vm_script_createcacheddata"><code>script.createCachedData()</code></a></li> 151<li><a href="#vm_script_runincontext_contextifiedobject_options"><code>script.runInContext(contextifiedObject[, options])</code></a></li> 152<li><a href="#vm_script_runinnewcontext_contextobject_options"><code>script.runInNewContext([contextObject[, options]])</code></a></li> 153<li><a href="#vm_script_runinthiscontext_options"><code>script.runInThisContext([options])</code></a></li> 154</ul> 155</li> 156<li><span class="stability_1"><a href="#vm_class_vm_module">Class: <code>vm.Module</code></a></span> 157<ul> 158<li><a href="#vm_module_dependencyspecifiers"><code>module.dependencySpecifiers</code></a></li> 159<li><a href="#vm_module_error"><code>module.error</code></a></li> 160<li><a href="#vm_module_evaluate_options"><code>module.evaluate([options])</code></a></li> 161<li><a href="#vm_module_identifier"><code>module.identifier</code></a></li> 162<li><a href="#vm_module_link_linker"><code>module.link(linker)</code></a></li> 163<li><a href="#vm_module_namespace"><code>module.namespace</code></a></li> 164<li><a href="#vm_module_status"><code>module.status</code></a></li> 165</ul> 166</li> 167<li><span class="stability_1"><a href="#vm_class_vm_sourcetextmodule">Class: <code>vm.SourceTextModule</code></a></span> 168<ul> 169<li><a href="#vm_new_vm_sourcetextmodule_code_options"><code>new vm.SourceTextModule(code[, options])</code></a></li> 170<li><a href="#vm_sourcetextmodule_createcacheddata"><code>sourceTextModule.createCachedData()</code></a></li> 171</ul> 172</li> 173<li><span class="stability_1"><a href="#vm_class_vm_syntheticmodule">Class: <code>vm.SyntheticModule</code></a></span> 174<ul> 175<li><a href="#vm_new_vm_syntheticmodule_exportnames_evaluatecallback_options"><code>new vm.SyntheticModule(exportNames, evaluateCallback[, options])</code></a></li> 176<li><a href="#vm_syntheticmodule_setexport_name_value"><code>syntheticModule.setExport(name, value)</code></a></li> 177</ul> 178</li> 179<li><a href="#vm_vm_compilefunction_code_params_options"><code>vm.compileFunction(code[, params[, options]])</code></a></li> 180<li><a href="#vm_vm_createcontext_contextobject_options"><code>vm.createContext([contextObject[, options]])</code></a></li> 181<li><a href="#vm_vm_iscontext_object"><code>vm.isContext(object)</code></a></li> 182<li><span class="stability_1"><a href="#vm_vm_measurememory_options"><code>vm.measureMemory([options])</code></a></span></li> 183<li><a href="#vm_vm_runincontext_code_contextifiedobject_options"><code>vm.runInContext(code, contextifiedObject[, options])</code></a></li> 184<li><a href="#vm_vm_runinnewcontext_code_contextobject_options"><code>vm.runInNewContext(code[, contextObject[, options]])</code></a></li> 185<li><a href="#vm_vm_runinthiscontext_code_options"><code>vm.runInThisContext(code[, options])</code></a></li> 186<li><a href="#vm_example_running_an_http_server_within_a_vm">Example: Running an HTTP server within a VM</a></li> 187<li><a href="#vm_what_does_it_mean_to_contextify_an_object">What does it mean to "contextify" an object?</a></li> 188<li><a href="#vm_timeout_interactions_with_asynchronous_tasks_and_promises">Timeout interactions with asynchronous tasks and Promises</a></li> 189</ul> 190</li> 191</ul></details> 192 193 <div id="apicontent"> 194 <h2>VM (executing JavaScript)<span><a class="mark" href="#vm_vm_executing_javascript" id="vm_vm_executing_javascript">#</a></span></h2> 195 196<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 197 198<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v14.20.1/lib/vm.js">lib/vm.js</a></p> 199<p>The <code>vm</code> module enables compiling and running code within V8 Virtual 200Machine contexts. <strong>The <code>vm</code> module is not a security mechanism. Do 201not use it to run untrusted code</strong>.</p> 202<p>JavaScript code can be compiled and run immediately or 203compiled, saved, and run later.</p> 204<p>A common use case is to run the code in a different V8 Context. This means 205invoked code has a different global object than the invoking code.</p> 206<p>One can provide the context by <a href="#vm_what_does_it_mean_to_contextify_an_object"><em>contextifying</em></a> an 207object. The invoked code treats any property in the context like a 208global variable. Any changes to global variables caused by the invoked 209code are reflected in the context object.</p> 210<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 211 212<span class="hljs-keyword">const</span> x = <span class="hljs-number">1</span>; 213 214<span class="hljs-keyword">const</span> context = { <span class="hljs-attr">x</span>: <span class="hljs-number">2</span> }; 215vm.<span class="hljs-title function_">createContext</span>(context); <span class="hljs-comment">// Contextify the object.</span> 216 217<span class="hljs-keyword">const</span> code = <span class="hljs-string">'x += 40; var y = 17;'</span>; 218<span class="hljs-comment">// `x` and `y` are global variables in the context.</span> 219<span class="hljs-comment">// Initially, x has the value 2 because that is the value of context.x.</span> 220vm.<span class="hljs-title function_">runInContext</span>(code, context); 221 222<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(context.<span class="hljs-property">x</span>); <span class="hljs-comment">// 42</span> 223<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(context.<span class="hljs-property">y</span>); <span class="hljs-comment">// 17</span> 224 225<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(x); <span class="hljs-comment">// 1; y is not defined.</span></code></pre> 226<section><h3>Class: <code>vm.Script</code><span><a class="mark" href="#vm_class_vm_script" id="vm_class_vm_script">#</a></span></h3> 227<div class="api_metadata"> 228<span>Added in: v0.3.1</span> 229</div> 230<p>Instances of the <code>vm.Script</code> class contain precompiled scripts that can be 231executed in specific contexts.</p> 232<h4><code>new vm.Script(code[, options])</code><span><a class="mark" href="#vm_new_vm_script_code_options" id="vm_new_vm_script_code_options">#</a></span></h4> 233<div class="api_metadata"> 234<details class="changelog"><summary>History</summary> 235<table> 236<tbody><tr><th>Version</th><th>Changes</th></tr> 237<tr><td>v10.6.0</td> 238<td><p>The <code>produceCachedData</code> is deprecated in favour of <code>script.createCachedData()</code>.</p></td></tr> 239<tr><td>v5.7.0</td> 240<td><p>The <code>cachedData</code> and <code>produceCachedData</code> options are supported now.</p></td></tr> 241<tr><td>v0.3.1</td> 242<td><p><span>Added in: v0.3.1</span></p></td></tr> 243</tbody></table> 244</details> 245</div> 246<ul> 247<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The JavaScript code to compile.</li> 248<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> 249<ul> 250<li><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Specifies the filename used in stack traces produced 251by this script. <strong>Default:</strong> <code>'evalmachine.<anonymous>'</code>.</li> 252<li><code>lineOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the line number offset that is displayed 253in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 254<li><code>columnOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the first-line column number offset that 255is displayed in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 256<li><code>cachedData</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> Provides an optional <code>Buffer</code> or 257<code>TypedArray</code>, or <code>DataView</code> with V8's code cache data for the supplied 258source. When supplied, the <code>cachedDataRejected</code> value will be set to 259either <code>true</code> or <code>false</code> depending on acceptance of the data by V8.</li> 260<li><code>produceCachedData</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code> and no <code>cachedData</code> is present, V8 261will attempt to produce code cache data for <code>code</code>. Upon success, a 262<code>Buffer</code> with V8's code cache data will be produced and stored in the 263<code>cachedData</code> property of the returned <code>vm.Script</code> instance. 264The <code>cachedDataProduced</code> value will be set to either <code>true</code> or <code>false</code> 265depending on whether code cache data is produced successfully. 266This option is <strong>deprecated</strong> in favor of <code>script.createCachedData()</code>. 267<strong>Default:</strong> <code>false</code>.</li> 268<li><code>importModuleDynamically</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called during evaluation of this module 269when <code>import()</code> is called. If this option is not specified, calls to 270<code>import()</code> will reject with <a href="errors.html#ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING"><code>ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING</code></a>. 271This option is part of the experimental modules API. We do not recommend 272using it in a production environment. 273<ul> 274<li><code>specifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> specifier passed to <code>import()</code></li> 275<li><code>script</code> <a href="vm.html#vm_class_vm_script" class="type"><vm.Script></a></li> 276<li>Returns: <a href="https://tc39.github.io/ecma262/#sec-module-namespace-exotic-objects" class="type"><Module Namespace Object></a> | <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a> Returning a <code>vm.Module</code> is 277recommended in order to take advantage of error tracking, and to avoid 278issues with namespaces that contain <code>then</code> function exports.</li> 279</ul> 280</li> 281</ul> 282</li> 283</ul> 284<p>If <code>options</code> is a string, then it specifies the filename.</p> 285<p>Creating a new <code>vm.Script</code> object compiles <code>code</code> but does not run it. The 286compiled <code>vm.Script</code> can be run later multiple times. The <code>code</code> is not bound to 287any global object; rather, it is bound before each run, just for that run.</p> 288<h4><code>script.createCachedData()</code><span><a class="mark" href="#vm_script_createcacheddata" id="vm_script_createcacheddata">#</a></span></h4> 289<div class="api_metadata"> 290<span>Added in: v10.6.0</span> 291</div> 292<ul> 293<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> 294</ul> 295<p>Creates a code cache that can be used with the <code>Script</code> constructor's 296<code>cachedData</code> option. Returns a <code>Buffer</code>. This method may be called at any 297time and any number of times.</p> 298<pre><code class="language-js"><span class="hljs-keyword">const</span> script = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">Script</span>(<span class="hljs-string">` 299function add(a, b) { 300 return a + b; 301} 302 303const x = add(1, 2); 304`</span>); 305 306<span class="hljs-keyword">const</span> cacheWithoutX = script.<span class="hljs-title function_">createCachedData</span>(); 307 308script.<span class="hljs-title function_">runInThisContext</span>(); 309 310<span class="hljs-keyword">const</span> cacheWithX = script.<span class="hljs-title function_">createCachedData</span>();</code></pre> 311<h4><code>script.runInContext(contextifiedObject[, options])</code><span><a class="mark" href="#vm_script_runincontext_contextifiedobject_options" id="vm_script_runincontext_contextifiedobject_options">#</a></span></h4> 312<div class="api_metadata"> 313<details class="changelog"><summary>History</summary> 314<table> 315<tbody><tr><th>Version</th><th>Changes</th></tr> 316<tr><td>v6.3.0</td> 317<td><p>The <code>breakOnSigint</code> option is supported now.</p></td></tr> 318<tr><td>v0.3.1</td> 319<td><p><span>Added in: v0.3.1</span></p></td></tr> 320</tbody></table> 321</details> 322</div> 323<ul> 324<li><code>contextifiedObject</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> A <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> object as returned by the 325<code>vm.createContext()</code> method.</li> 326<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 327<ul> 328<li><code>displayErrors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, if an <a href="errors.html#errors_class_error"><code>Error</code></a> occurs 329while compiling the <code>code</code>, the line of code causing the error is attached 330to the stack trace. <strong>Default:</strong> <code>true</code>.</li> 331<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the number of milliseconds to execute <code>code</code> 332before terminating execution. If execution is terminated, an <a href="errors.html#errors_class_error"><code>Error</code></a> 333will be thrown. This value must be a strictly positive integer.</li> 334<li><code>breakOnSigint</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, receiving <code>SIGINT</code> 335(<kbd>Ctrl</kbd>+<kbd>C</kbd>) will terminate execution and throw an 336<a href="errors.html#errors_class_error"><code>Error</code></a>. Existing handlers for the event that have been attached via 337<code>process.on('SIGINT')</code> are disabled during script execution, but continue to 338work after that. <strong>Default:</strong> <code>false</code>.</li> 339</ul> 340</li> 341<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the result of the very last statement executed in the script.</li> 342</ul> 343<p>Runs the compiled code contained by the <code>vm.Script</code> object within the given 344<code>contextifiedObject</code> and returns the result. Running code does not have access 345to local scope.</p> 346<p>The following example compiles code that increments a global variable, sets 347the value of another global variable, then execute the code multiple times. 348The globals are contained in the <code>context</code> object.</p> 349<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 350 351<span class="hljs-keyword">const</span> context = { 352 <span class="hljs-attr">animal</span>: <span class="hljs-string">'cat'</span>, 353 <span class="hljs-attr">count</span>: <span class="hljs-number">2</span> 354}; 355 356<span class="hljs-keyword">const</span> script = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">Script</span>(<span class="hljs-string">'count += 1; name = "kitty";'</span>); 357 358vm.<span class="hljs-title function_">createContext</span>(context); 359<span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> i = <span class="hljs-number">0</span>; i < <span class="hljs-number">10</span>; ++i) { 360 script.<span class="hljs-title function_">runInContext</span>(context); 361} 362 363<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(context); 364<span class="hljs-comment">// Prints: { animal: 'cat', count: 12, name: 'kitty' }</span></code></pre> 365<p>Using the <code>timeout</code> or <code>breakOnSigint</code> options will result in new event loops 366and corresponding threads being started, which have a non-zero performance 367overhead.</p> 368<h4><code>script.runInNewContext([contextObject[, options]])</code><span><a class="mark" href="#vm_script_runinnewcontext_contextobject_options" id="vm_script_runinnewcontext_contextobject_options">#</a></span></h4> 369<div class="api_metadata"> 370<details class="changelog"><summary>History</summary> 371<table> 372<tbody><tr><th>Version</th><th>Changes</th></tr> 373<tr><td>v14.6.0</td> 374<td><p>The <code>microtaskMode</code> option is supported now.</p></td></tr> 375<tr><td>v10.0.0</td> 376<td><p>The <code>contextCodeGeneration</code> option is supported now.</p></td></tr> 377<tr><td>v6.3.0</td> 378<td><p>The <code>breakOnSigint</code> option is supported now.</p></td></tr> 379<tr><td>v0.3.1</td> 380<td><p><span>Added in: v0.3.1</span></p></td></tr> 381</tbody></table> 382</details> 383</div> 384<ul> 385<li><code>contextObject</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> An object that will be <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a>. If 386<code>undefined</code>, a new object will be created.</li> 387<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 388<ul> 389<li><code>displayErrors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, if an <a href="errors.html#errors_class_error"><code>Error</code></a> occurs 390while compiling the <code>code</code>, the line of code causing the error is attached 391to the stack trace. <strong>Default:</strong> <code>true</code>.</li> 392<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the number of milliseconds to execute <code>code</code> 393before terminating execution. If execution is terminated, an <a href="errors.html#errors_class_error"><code>Error</code></a> 394will be thrown. This value must be a strictly positive integer.</li> 395<li><code>breakOnSigint</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, receiving <code>SIGINT</code> 396(<kbd>Ctrl</kbd>+<kbd>C</kbd>) will terminate execution and throw an 397<a href="errors.html#errors_class_error"><code>Error</code></a>. Existing handlers for the event that have been attached via 398<code>process.on('SIGINT')</code> are disabled during script execution, but continue to 399work after that. <strong>Default:</strong> <code>false</code>.</li> 400<li><code>contextName</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Human-readable name of the newly created context. 401<strong>Default:</strong> <code>'VM Context i'</code>, where <code>i</code> is an ascending numerical index of 402the created context.</li> 403<li><code>contextOrigin</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <a href="https://developer.mozilla.org/en-US/docs/Glossary/Origin">Origin</a> corresponding to the newly 404created context for display purposes. The origin should be formatted like a 405URL, but with only the scheme, host, and port (if necessary), like the 406value of the <a href="url.html#url_url_origin"><code>url.origin</code></a> property of a <a href="url.html#url_class_url"><code>URL</code></a> object. Most notably, 407this string should omit the trailing slash, as that denotes a path. 408<strong>Default:</strong> <code>''</code>.</li> 409<li><code>contextCodeGeneration</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 410<ul> 411<li><code>strings</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to false any calls to <code>eval</code> or function 412constructors (<code>Function</code>, <code>GeneratorFunction</code>, etc) will throw an 413<code>EvalError</code>. <strong>Default:</strong> <code>true</code>.</li> 414<li><code>wasm</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to false any attempt to compile a WebAssembly 415module will throw a <code>WebAssembly.CompileError</code>. <strong>Default:</strong> <code>true</code>.</li> 416</ul> 417</li> 418<li><code>microtaskMode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If set to <code>afterEvaluate</code>, microtasks (tasks 419scheduled through <code>Promise</code>s and <code>async function</code>s) will be run immediately 420after the script has run. They are included in the <code>timeout</code> and 421<code>breakOnSigint</code> scopes in that case.</li> 422</ul> 423</li> 424<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the result of the very last statement executed in the script.</li> 425</ul> 426<p>First contextifies the given <code>contextObject</code>, runs the compiled code contained 427by the <code>vm.Script</code> object within the created context, and returns the result. 428Running code does not have access to local scope.</p> 429<p>The following example compiles code that sets a global variable, then executes 430the code multiple times in different contexts. The globals are set on and 431contained within each individual <code>context</code>.</p> 432<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 433 434<span class="hljs-keyword">const</span> script = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">Script</span>(<span class="hljs-string">'globalVar = "set"'</span>); 435 436<span class="hljs-keyword">const</span> contexts = [{}, {}, {}]; 437contexts.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">context</span>) =></span> { 438 script.<span class="hljs-title function_">runInNewContext</span>(context); 439}); 440 441<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(contexts); 442<span class="hljs-comment">// Prints: [{ globalVar: 'set' }, { globalVar: 'set' }, { globalVar: 'set' }]</span></code></pre> 443<h4><code>script.runInThisContext([options])</code><span><a class="mark" href="#vm_script_runinthiscontext_options" id="vm_script_runinthiscontext_options">#</a></span></h4> 444<div class="api_metadata"> 445<details class="changelog"><summary>History</summary> 446<table> 447<tbody><tr><th>Version</th><th>Changes</th></tr> 448<tr><td>v6.3.0</td> 449<td><p>The <code>breakOnSigint</code> option is supported now.</p></td></tr> 450<tr><td>v0.3.1</td> 451<td><p><span>Added in: v0.3.1</span></p></td></tr> 452</tbody></table> 453</details> 454</div> 455<ul> 456<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 457<ul> 458<li><code>displayErrors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, if an <a href="errors.html#errors_class_error"><code>Error</code></a> occurs 459while compiling the <code>code</code>, the line of code causing the error is attached 460to the stack trace. <strong>Default:</strong> <code>true</code>.</li> 461<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the number of milliseconds to execute <code>code</code> 462before terminating execution. If execution is terminated, an <a href="errors.html#errors_class_error"><code>Error</code></a> 463will be thrown. This value must be a strictly positive integer.</li> 464<li><code>breakOnSigint</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, receiving <code>SIGINT</code> 465(<kbd>Ctrl</kbd>+<kbd>C</kbd>) will terminate execution and throw an 466<a href="errors.html#errors_class_error"><code>Error</code></a>. Existing handlers for the event that have been attached via 467<code>process.on('SIGINT')</code> are disabled during script execution, but continue to 468work after that. <strong>Default:</strong> <code>false</code>.</li> 469</ul> 470</li> 471<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the result of the very last statement executed in the script.</li> 472</ul> 473<p>Runs the compiled code contained by the <code>vm.Script</code> within the context of the 474current <code>global</code> object. Running code does not have access to local scope, but 475<em>does</em> have access to the current <code>global</code> object.</p> 476<p>The following example compiles code that increments a <code>global</code> variable then 477executes that code multiple times:</p> 478<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 479 480<span class="hljs-variable language_">global</span>.<span class="hljs-property">globalVar</span> = <span class="hljs-number">0</span>; 481 482<span class="hljs-keyword">const</span> script = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">Script</span>(<span class="hljs-string">'globalVar += 1'</span>, { <span class="hljs-attr">filename</span>: <span class="hljs-string">'myfile.vm'</span> }); 483 484<span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> i = <span class="hljs-number">0</span>; i < <span class="hljs-number">1000</span>; ++i) { 485 script.<span class="hljs-title function_">runInThisContext</span>(); 486} 487 488<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(globalVar); 489 490<span class="hljs-comment">// 1000</span></code></pre> 491</section><section><h3>Class: <code>vm.Module</code><span><a class="mark" href="#vm_class_vm_module" id="vm_class_vm_module">#</a></span></h3> 492<div class="api_metadata"> 493<span>Added in: v13.0.0, v12.16.0</span> 494</div> 495<p></p><div class="api_stability api_stability_1"><a href="documentation.html#documentation_stability_index">Stability: 1</a> - Experimental</div><p></p> 496<p>This feature is only available with the <code>--experimental-vm-modules</code> command 497flag enabled.</p> 498<p>The <code>vm.Module</code> class provides a low-level interface for using 499ECMAScript modules in VM contexts. It is the counterpart of the <code>vm.Script</code> 500class that closely mirrors <a href="https://www.ecma-international.org/ecma-262/#sec-abstract-module-records">Module Record</a>s as defined in the ECMAScript 501specification.</p> 502<p>Unlike <code>vm.Script</code> however, every <code>vm.Module</code> object is bound to a context from 503its creation. Operations on <code>vm.Module</code> objects are intrinsically asynchronous, 504in contrast with the synchronous nature of <code>vm.Script</code> objects. The use of 505'async' functions can help with manipulating <code>vm.Module</code> objects.</p> 506<p>Using a <code>vm.Module</code> object requires three distinct steps: creation/parsing, 507linking, and evaluation. These three steps are illustrated in the following 508example.</p> 509<p>This implementation lies at a lower level than the <a href="esm.html#esm_modules_ecmascript_modules">ECMAScript Module 510loader</a>. There is also no way to interact with the Loader yet, though 511support is planned.</p> 512 513<pre><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> vm <span class="hljs-keyword">from</span> <span class="hljs-string">'vm'</span>; 514 515<span class="hljs-keyword">const</span> contextifiedObject = vm.<span class="hljs-title function_">createContext</span>({ 516 <span class="hljs-attr">secret</span>: <span class="hljs-number">42</span>, 517 <span class="hljs-attr">print</span>: <span class="hljs-variable language_">console</span>.<span class="hljs-property">log</span>, 518}); 519 520<span class="hljs-comment">// Step 1</span> 521<span class="hljs-comment">//</span> 522<span class="hljs-comment">// Create a Module by constructing a new `vm.SourceTextModule` object. This</span> 523<span class="hljs-comment">// parses the provided source text, throwing a `SyntaxError` if anything goes</span> 524<span class="hljs-comment">// wrong. By default, a Module is created in the top context. But here, we</span> 525<span class="hljs-comment">// specify `contextifiedObject` as the context this Module belongs to.</span> 526<span class="hljs-comment">//</span> 527<span class="hljs-comment">// Here, we attempt to obtain the default export from the module "foo", and</span> 528<span class="hljs-comment">// put it into local binding "secret".</span> 529 530<span class="hljs-keyword">const</span> bar = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>(<span class="hljs-string">` 531 import s from 'foo'; 532 s; 533 print(s); 534`</span>, { <span class="hljs-attr">context</span>: contextifiedObject }); 535 536<span class="hljs-comment">// Step 2</span> 537<span class="hljs-comment">//</span> 538<span class="hljs-comment">// "Link" the imported dependencies of this Module to it.</span> 539<span class="hljs-comment">//</span> 540<span class="hljs-comment">// The provided linking callback (the "linker") accepts two arguments: the</span> 541<span class="hljs-comment">// parent module (`bar` in this case) and the string that is the specifier of</span> 542<span class="hljs-comment">// the imported module. The callback is expected to return a Module that</span> 543<span class="hljs-comment">// corresponds to the provided specifier, with certain requirements documented</span> 544<span class="hljs-comment">// in `module.link()`.</span> 545<span class="hljs-comment">//</span> 546<span class="hljs-comment">// If linking has not started for the returned Module, the same linker</span> 547<span class="hljs-comment">// callback will be called on the returned Module.</span> 548<span class="hljs-comment">//</span> 549<span class="hljs-comment">// Even top-level Modules without dependencies must be explicitly linked. The</span> 550<span class="hljs-comment">// callback provided would never be called, however.</span> 551<span class="hljs-comment">//</span> 552<span class="hljs-comment">// The link() method returns a Promise that will be resolved when all the</span> 553<span class="hljs-comment">// Promises returned by the linker resolve.</span> 554<span class="hljs-comment">//</span> 555<span class="hljs-comment">// Note: This is a contrived example in that the linker function creates a new</span> 556<span class="hljs-comment">// "foo" module every time it is called. In a full-fledged module system, a</span> 557<span class="hljs-comment">// cache would probably be used to avoid duplicated modules.</span> 558 559<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">linker</span>(<span class="hljs-params">specifier, referencingModule</span>) { 560 <span class="hljs-keyword">if</span> (specifier === <span class="hljs-string">'foo'</span>) { 561 <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>(<span class="hljs-string">` 562 // The "secret" variable refers to the global variable we added to 563 // "contextifiedObject" when creating the context. 564 export default secret; 565 `</span>, { <span class="hljs-attr">context</span>: referencingModule.<span class="hljs-property">context</span> }); 566 567 <span class="hljs-comment">// Using `contextifiedObject` instead of `referencingModule.context`</span> 568 <span class="hljs-comment">// here would work as well.</span> 569 } 570 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">`Unable to resolve dependency: <span class="hljs-subst">${specifier}</span>`</span>); 571} 572<span class="hljs-keyword">await</span> bar.<span class="hljs-title function_">link</span>(linker); 573 574<span class="hljs-comment">// Step 3</span> 575<span class="hljs-comment">//</span> 576<span class="hljs-comment">// Evaluate the Module. The evaluate() method returns a promise which will</span> 577<span class="hljs-comment">// resolve after the module has finished evaluating.</span> 578 579<span class="hljs-comment">// Prints 42.</span> 580<span class="hljs-keyword">await</span> bar.evaluate();</code><code class="language-js cjs"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 581 582<span class="hljs-keyword">const</span> contextifiedObject = vm.<span class="hljs-title function_">createContext</span>({ 583 <span class="hljs-attr">secret</span>: <span class="hljs-number">42</span>, 584 <span class="hljs-attr">print</span>: <span class="hljs-variable language_">console</span>.<span class="hljs-property">log</span>, 585}); 586 587(<span class="hljs-keyword">async</span> () => { 588 <span class="hljs-comment">// Step 1</span> 589 <span class="hljs-comment">//</span> 590 <span class="hljs-comment">// Create a Module by constructing a new `vm.SourceTextModule` object. This</span> 591 <span class="hljs-comment">// parses the provided source text, throwing a `SyntaxError` if anything goes</span> 592 <span class="hljs-comment">// wrong. By default, a Module is created in the top context. But here, we</span> 593 <span class="hljs-comment">// specify `contextifiedObject` as the context this Module belongs to.</span> 594 <span class="hljs-comment">//</span> 595 <span class="hljs-comment">// Here, we attempt to obtain the default export from the module "foo", and</span> 596 <span class="hljs-comment">// put it into local binding "secret".</span> 597 598 <span class="hljs-keyword">const</span> bar = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>(<span class="hljs-string">` 599 import s from 'foo'; 600 s; 601 print(s); 602 `</span>, { <span class="hljs-attr">context</span>: contextifiedObject }); 603 604 <span class="hljs-comment">// Step 2</span> 605 <span class="hljs-comment">//</span> 606 <span class="hljs-comment">// "Link" the imported dependencies of this Module to it.</span> 607 <span class="hljs-comment">//</span> 608 <span class="hljs-comment">// The provided linking callback (the "linker") accepts two arguments: the</span> 609 <span class="hljs-comment">// parent module (`bar` in this case) and the string that is the specifier of</span> 610 <span class="hljs-comment">// the imported module. The callback is expected to return a Module that</span> 611 <span class="hljs-comment">// corresponds to the provided specifier, with certain requirements documented</span> 612 <span class="hljs-comment">// in `module.link()`.</span> 613 <span class="hljs-comment">//</span> 614 <span class="hljs-comment">// If linking has not started for the returned Module, the same linker</span> 615 <span class="hljs-comment">// callback will be called on the returned Module.</span> 616 <span class="hljs-comment">//</span> 617 <span class="hljs-comment">// Even top-level Modules without dependencies must be explicitly linked. The</span> 618 <span class="hljs-comment">// callback provided would never be called, however.</span> 619 <span class="hljs-comment">//</span> 620 <span class="hljs-comment">// The link() method returns a Promise that will be resolved when all the</span> 621 <span class="hljs-comment">// Promises returned by the linker resolve.</span> 622 <span class="hljs-comment">//</span> 623 <span class="hljs-comment">// Note: This is a contrived example in that the linker function creates a new</span> 624 <span class="hljs-comment">// "foo" module every time it is called. In a full-fledged module system, a</span> 625 <span class="hljs-comment">// cache would probably be used to avoid duplicated modules.</span> 626 627 <span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">linker</span>(<span class="hljs-params">specifier, referencingModule</span>) { 628 <span class="hljs-keyword">if</span> (specifier === <span class="hljs-string">'foo'</span>) { 629 <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>(<span class="hljs-string">` 630 // The "secret" variable refers to the global variable we added to 631 // "contextifiedObject" when creating the context. 632 export default secret; 633 `</span>, { <span class="hljs-attr">context</span>: referencingModule.<span class="hljs-property">context</span> }); 634 635 <span class="hljs-comment">// Using `contextifiedObject` instead of `referencingModule.context`</span> 636 <span class="hljs-comment">// here would work as well.</span> 637 } 638 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">`Unable to resolve dependency: <span class="hljs-subst">${specifier}</span>`</span>); 639 } 640 <span class="hljs-keyword">await</span> bar.<span class="hljs-title function_">link</span>(linker); 641 642 <span class="hljs-comment">// Step 3</span> 643 <span class="hljs-comment">//</span> 644 <span class="hljs-comment">// Evaluate the Module. The evaluate() method returns a promise which will</span> 645 <span class="hljs-comment">// resolve after the module has finished evaluating.</span> 646 647 <span class="hljs-comment">// Prints 42.</span> 648 <span class="hljs-keyword">await</span> bar.evaluate(); 649})();</code></pre> 650<h4><code>module.dependencySpecifiers</code><span><a class="mark" href="#vm_module_dependencyspecifiers" id="vm_module_dependencyspecifiers">#</a></span></h4> 651<ul> 652<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 653</ul> 654<p>The specifiers of all dependencies of this module. The returned array is frozen 655to disallow any changes to it.</p> 656<p>Corresponds to the <code>[[RequestedModules]]</code> field of <a href="https://tc39.es/ecma262/#sec-cyclic-module-records">Cyclic Module Record</a>s in 657the ECMAScript specification.</p> 658<h4><code>module.error</code><span><a class="mark" href="#vm_module_error" id="vm_module_error">#</a></span></h4> 659<ul> 660<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 661</ul> 662<p>If the <code>module.status</code> is <code>'errored'</code>, this property contains the exception 663thrown by the module during evaluation. If the status is anything else, 664accessing this property will result in a thrown exception.</p> 665<p>The value <code>undefined</code> cannot be used for cases where there is not a thrown 666exception due to possible ambiguity with <code>throw undefined;</code>.</p> 667<p>Corresponds to the <code>[[EvaluationError]]</code> field of <a href="https://tc39.es/ecma262/#sec-cyclic-module-records">Cyclic Module Record</a>s 668in the ECMAScript specification.</p> 669<h4><code>module.evaluate([options])</code><span><a class="mark" href="#vm_module_evaluate_options" id="vm_module_evaluate_options">#</a></span></h4> 670<ul> 671<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 672<ul> 673<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the number of milliseconds to evaluate 674before terminating execution. If execution is interrupted, an <a href="errors.html#errors_class_error"><code>Error</code></a> 675will be thrown. This value must be a strictly positive integer.</li> 676<li><code>breakOnSigint</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, receiving <code>SIGINT</code> 677(<kbd>Ctrl</kbd>+<kbd>C</kbd>) will terminate execution and throw an 678<a href="errors.html#errors_class_error"><code>Error</code></a>. Existing handlers for the event that have been attached via 679<code>process.on('SIGINT')</code> are disabled during script execution, but continue to 680work after that. <strong>Default:</strong> <code>false</code>.</li> 681</ul> 682</li> 683<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with <code>undefined</code> upon success.</li> 684</ul> 685<p>Evaluate the module.</p> 686<p>This must be called after the module has been linked; otherwise it will reject. 687It could be called also when the module has already been evaluated, in which 688case it will either do nothing if the initial evaluation ended in success 689(<code>module.status</code> is <code>'evaluated'</code>) or it will re-throw the exception that the 690initial evaluation resulted in (<code>module.status</code> is <code>'errored'</code>).</p> 691<p>This method cannot be called while the module is being evaluated 692(<code>module.status</code> is <code>'evaluating'</code>).</p> 693<p>Corresponds to the <a href="https://tc39.es/ecma262/#sec-moduleevaluation">Evaluate() concrete method</a> field of <a href="https://tc39.es/ecma262/#sec-cyclic-module-records">Cyclic Module 694Record</a>s in the ECMAScript specification.</p> 695<h4><code>module.identifier</code><span><a class="mark" href="#vm_module_identifier" id="vm_module_identifier">#</a></span></h4> 696<ul> 697<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 698</ul> 699<p>The identifier of the current module, as set in the constructor.</p> 700<h4><code>module.link(linker)</code><span><a class="mark" href="#vm_module_link_linker" id="vm_module_link_linker">#</a></span></h4> 701<ul> 702<li><code>linker</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 703<ul> 704<li> 705<p><code>specifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The specifier of the requested module:</p> 706<pre><code class="language-js mjs"><span class="hljs-keyword">import</span> foo <span class="hljs-keyword">from</span> <span class="hljs-string">'foo'</span>; 707<span class="hljs-comment">// ^^^^^ the module specifier</span></code></pre> 708</li> 709<li> 710<p><code>referencingModule</code> <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a> The <code>Module</code> object <code>link()</code> is called on.</p> 711</li> 712<li> 713<p>Returns: <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a></p> 714</li> 715</ul> 716</li> 717<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a></li> 718</ul> 719<p>Link module dependencies. This method must be called before evaluation, and 720can only be called once per module.</p> 721<p>The function is expected to return a <code>Module</code> object or a <code>Promise</code> that 722eventually resolves to a <code>Module</code> object. The returned <code>Module</code> must satisfy the 723following two invariants:</p> 724<ul> 725<li>It must belong to the same context as the parent <code>Module</code>.</li> 726<li>Its <code>status</code> must not be <code>'errored'</code>.</li> 727</ul> 728<p>If the returned <code>Module</code>'s <code>status</code> is <code>'unlinked'</code>, this method will be 729recursively called on the returned <code>Module</code> with the same provided <code>linker</code> 730function.</p> 731<p><code>link()</code> returns a <code>Promise</code> that will either get resolved when all linking 732instances resolve to a valid <code>Module</code>, or rejected if the linker function either 733throws an exception or returns an invalid <code>Module</code>.</p> 734<p>The linker function roughly corresponds to the implementation-defined 735<a href="https://tc39.es/ecma262/#sec-hostresolveimportedmodule">HostResolveImportedModule</a> abstract operation in the ECMAScript 736specification, with a few key differences:</p> 737<ul> 738<li>The linker function is allowed to be asynchronous while 739<a href="https://tc39.es/ecma262/#sec-hostresolveimportedmodule">HostResolveImportedModule</a> is synchronous.</li> 740</ul> 741<p>The actual <a href="https://tc39.es/ecma262/#sec-hostresolveimportedmodule">HostResolveImportedModule</a> implementation used during module 742linking is one that returns the modules linked during linking. Since at 743that point all modules would have been fully linked already, the 744<a href="https://tc39.es/ecma262/#sec-hostresolveimportedmodule">HostResolveImportedModule</a> implementation is fully synchronous per 745specification.</p> 746<p>Corresponds to the <a href="https://tc39.es/ecma262/#sec-moduledeclarationlinking">Link() concrete method</a> field of <a href="https://tc39.es/ecma262/#sec-cyclic-module-records">Cyclic Module 747Record</a>s in the ECMAScript specification.</p> 748<h4><code>module.namespace</code><span><a class="mark" href="#vm_module_namespace" id="vm_module_namespace">#</a></span></h4> 749<ul> 750<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 751</ul> 752<p>The namespace object of the module. This is only available after linking 753(<code>module.link()</code>) has completed.</p> 754<p>Corresponds to the <a href="https://tc39.es/ecma262/#sec-getmodulenamespace">GetModuleNamespace</a> abstract operation in the ECMAScript 755specification.</p> 756<h4><code>module.status</code><span><a class="mark" href="#vm_module_status" id="vm_module_status">#</a></span></h4> 757<ul> 758<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 759</ul> 760<p>The current status of the module. Will be one of:</p> 761<ul> 762<li> 763<p><code>'unlinked'</code>: <code>module.link()</code> has not yet been called.</p> 764</li> 765<li> 766<p><code>'linking'</code>: <code>module.link()</code> has been called, but not all Promises returned 767by the linker function have been resolved yet.</p> 768</li> 769<li> 770<p><code>'linked'</code>: The module has been linked successfully, and all of its 771dependencies are linked, but <code>module.evaluate()</code> has not yet been called.</p> 772</li> 773<li> 774<p><code>'evaluating'</code>: The module is being evaluated through a <code>module.evaluate()</code> on 775itself or a parent module.</p> 776</li> 777<li> 778<p><code>'evaluated'</code>: The module has been successfully evaluated.</p> 779</li> 780<li> 781<p><code>'errored'</code>: The module has been evaluated, but an exception was thrown.</p> 782</li> 783</ul> 784<p>Other than <code>'errored'</code>, this status string corresponds to the specification's 785<a href="https://tc39.es/ecma262/#sec-cyclic-module-records">Cyclic Module Record</a>'s <code>[[Status]]</code> field. <code>'errored'</code> corresponds to 786<code>'evaluated'</code> in the specification, but with <code>[[EvaluationError]]</code> set to a 787value that is not <code>undefined</code>.</p> 788</section><section><h3>Class: <code>vm.SourceTextModule</code><span><a class="mark" href="#vm_class_vm_sourcetextmodule" id="vm_class_vm_sourcetextmodule">#</a></span></h3> 789<div class="api_metadata"> 790<span>Added in: v9.6.0</span> 791</div> 792<p></p><div class="api_stability api_stability_1"><a href="documentation.html#documentation_stability_index">Stability: 1</a> - Experimental</div><p></p> 793<p>This feature is only available with the <code>--experimental-vm-modules</code> command 794flag enabled.</p> 795<ul> 796<li>Extends: <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a></li> 797</ul> 798<p>The <code>vm.SourceTextModule</code> class provides the <a href="https://tc39.es/ecma262/#sec-source-text-module-records">Source Text Module Record</a> as 799defined in the ECMAScript specification.</p> 800<h4><code>new vm.SourceTextModule(code[, options])</code><span><a class="mark" href="#vm_new_vm_sourcetextmodule_code_options" id="vm_new_vm_sourcetextmodule_code_options">#</a></span></h4> 801<ul> 802<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> JavaScript Module code to parse</li> 803<li><code>options</code> 804<ul> 805<li><code>identifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> String used in stack traces. 806<strong>Default:</strong> <code>'vm:module(i)'</code> where <code>i</code> is a context-specific ascending 807index.</li> 808<li><code>cachedData</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> Provides an optional <code>Buffer</code> or 809<code>TypedArray</code>, or <code>DataView</code> with V8's code cache data for the supplied 810source. The <code>code</code> must be the same as the module from which this 811<code>cachedData</code> was created.</li> 812<li><code>context</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> object as returned by the 813<code>vm.createContext()</code> method, to compile and evaluate this <code>Module</code> in.</li> 814<li><code>lineOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the line number offset that is displayed 815in stack traces produced by this <code>Module</code>. <strong>Default:</strong> <code>0</code>.</li> 816<li><code>columnOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the first-line column number offset that 817is displayed in stack traces produced by this <code>Module</code>. <strong>Default:</strong> <code>0</code>.</li> 818<li><code>initializeImportMeta</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called during evaluation of this <code>Module</code> 819to initialize the <code>import.meta</code>. 820<ul> 821<li><code>meta</code> <a href="esm.html#esm_import_meta" class="type"><import.meta></a></li> 822<li><code>module</code> <a href="vm.html#vm_class_vm_sourcetextmodule" class="type"><vm.SourceTextModule></a></li> 823</ul> 824</li> 825<li><code>importModuleDynamically</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called during evaluation of this module 826when <code>import()</code> is called. If this option is not specified, calls to 827<code>import()</code> will reject with <a href="errors.html#ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING"><code>ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING</code></a>. 828<ul> 829<li><code>specifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> specifier passed to <code>import()</code></li> 830<li><code>module</code> <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a></li> 831<li>Returns: <a href="https://tc39.github.io/ecma262/#sec-module-namespace-exotic-objects" class="type"><Module Namespace Object></a> | <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a> Returning a <code>vm.Module</code> is 832recommended in order to take advantage of error tracking, and to avoid 833issues with namespaces that contain <code>then</code> function exports.</li> 834</ul> 835</li> 836</ul> 837</li> 838</ul> 839<p>Creates a new <code>SourceTextModule</code> instance.</p> 840<p>Properties assigned to the <code>import.meta</code> object that are objects may 841allow the module to access information outside the specified <code>context</code>. Use 842<code>vm.runInContext()</code> to create objects in a specific context.</p> 843 844<pre><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> vm <span class="hljs-keyword">from</span> <span class="hljs-string">'vm'</span>; 845 846<span class="hljs-keyword">const</span> contextifiedObject = vm.<span class="hljs-title function_">createContext</span>({ <span class="hljs-attr">secret</span>: <span class="hljs-number">42</span> }); 847 848<span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>( 849 <span class="hljs-string">'Object.getPrototypeOf(import.meta.prop).secret = secret;'</span>, 850 { 851 <span class="hljs-title function_">initializeImportMeta</span>(<span class="hljs-params">meta</span>) { 852 <span class="hljs-comment">// Note: this object is created in the top context. As such,</span> 853 <span class="hljs-comment">// Object.getPrototypeOf(import.meta.prop) points to the</span> 854 <span class="hljs-comment">// Object.prototype in the top context rather than that in</span> 855 <span class="hljs-comment">// the contextified object.</span> 856 meta.<span class="hljs-property">prop</span> = {}; 857 } 858 }); 859<span class="hljs-comment">// Since module has no dependencies, the linker function will never be called.</span> 860<span class="hljs-keyword">await</span> <span class="hljs-variable language_">module</span>.<span class="hljs-title function_">link</span>(<span class="hljs-function">() =></span> {}); 861<span class="hljs-keyword">await</span> <span class="hljs-variable language_">module</span>.evaluate(); 862 863<span class="hljs-comment">// Now, Object.prototype.secret will be equal to 42.</span> 864<span class="hljs-comment">//</span> 865<span class="hljs-comment">// To fix this problem, replace</span> 866<span class="hljs-comment">// meta.prop = {};</span> 867<span class="hljs-comment">// above with</span> 868<span class="hljs-comment">// meta.prop = vm.runInContext('{}', contextifiedObject);</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 869<span class="hljs-keyword">const</span> contextifiedObject = vm.<span class="hljs-title function_">createContext</span>({ <span class="hljs-attr">secret</span>: <span class="hljs-number">42</span> }); 870(<span class="hljs-keyword">async</span> () => { 871 <span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>( 872 <span class="hljs-string">'Object.getPrototypeOf(import.meta.prop).secret = secret;'</span>, 873 { 874 <span class="hljs-title function_">initializeImportMeta</span>(<span class="hljs-params">meta</span>) { 875 <span class="hljs-comment">// Note: this object is created in the top context. As such,</span> 876 <span class="hljs-comment">// Object.getPrototypeOf(import.meta.prop) points to the</span> 877 <span class="hljs-comment">// Object.prototype in the top context rather than that in</span> 878 <span class="hljs-comment">// the contextified object.</span> 879 meta.<span class="hljs-property">prop</span> = {}; 880 } 881 }); 882 <span class="hljs-comment">// Since module has no dependencies, the linker function will never be called.</span> 883 <span class="hljs-keyword">await</span> <span class="hljs-variable language_">module</span>.<span class="hljs-title function_">link</span>(<span class="hljs-function">() =></span> {}); 884 <span class="hljs-keyword">await</span> <span class="hljs-variable language_">module</span>.evaluate(); 885 <span class="hljs-comment">// Now, Object.prototype.secret will be equal to 42.</span> 886 <span class="hljs-comment">//</span> 887 <span class="hljs-comment">// To fix this problem, replace</span> 888 <span class="hljs-comment">// meta.prop = {};</span> 889 <span class="hljs-comment">// above with</span> 890 <span class="hljs-comment">// meta.prop = vm.runInContext('{}', contextifiedObject);</span> 891})();</code></pre> 892<h4><code>sourceTextModule.createCachedData()</code><span><a class="mark" href="#vm_sourcetextmodule_createcacheddata" id="vm_sourcetextmodule_createcacheddata">#</a></span></h4> 893<div class="api_metadata"> 894<span>Added in: v13.7.0</span> 895</div> 896<ul> 897<li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> 898</ul> 899<p>Creates a code cache that can be used with the <code>SourceTextModule</code> constructor's 900<code>cachedData</code> option. Returns a <code>Buffer</code>. This method may be called any number 901of times before the module has been evaluated.</p> 902<pre><code class="language-js"><span class="hljs-comment">// Create an initial module</span> 903<span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>(<span class="hljs-string">'const a = 1;'</span>); 904 905<span class="hljs-comment">// Create cached data from this module</span> 906<span class="hljs-keyword">const</span> cachedData = <span class="hljs-variable language_">module</span>.<span class="hljs-title function_">createCachedData</span>(); 907 908<span class="hljs-comment">// Create a new module using the cached data. The code must be the same.</span> 909<span class="hljs-keyword">const</span> module2 = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SourceTextModule</span>(<span class="hljs-string">'const a = 1;'</span>, { cachedData });</code></pre> 910</section><section><h3>Class: <code>vm.SyntheticModule</code><span><a class="mark" href="#vm_class_vm_syntheticmodule" id="vm_class_vm_syntheticmodule">#</a></span></h3> 911<div class="api_metadata"> 912<span>Added in: v13.0.0, v12.16.0</span> 913</div> 914<p></p><div class="api_stability api_stability_1"><a href="documentation.html#documentation_stability_index">Stability: 1</a> - Experimental</div><p></p> 915<p>This feature is only available with the <code>--experimental-vm-modules</code> command 916flag enabled.</p> 917<ul> 918<li>Extends: <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a></li> 919</ul> 920<p>The <code>vm.SyntheticModule</code> class provides the <a href="https://heycam.github.io/webidl/#synthetic-module-records">Synthetic Module Record</a> as 921defined in the WebIDL specification. The purpose of synthetic modules is to 922provide a generic interface for exposing non-JavaScript sources to ECMAScript 923module graphs.</p> 924<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 925 926<span class="hljs-keyword">const</span> source = <span class="hljs-string">'{ "a": 1 }'</span>; 927<span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SyntheticModule</span>([<span class="hljs-string">'default'</span>], <span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) { 928 <span class="hljs-keyword">const</span> obj = <span class="hljs-variable constant_">JSON</span>.<span class="hljs-title function_">parse</span>(source); 929 <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setExport</span>(<span class="hljs-string">'default'</span>, obj); 930}); 931 932<span class="hljs-comment">// Use `module` in linking...</span></code></pre> 933<h4><code>new vm.SyntheticModule(exportNames, evaluateCallback[, options])</code><span><a class="mark" href="#vm_new_vm_syntheticmodule_exportnames_evaluatecallback_options" id="vm_new_vm_syntheticmodule_exportnames_evaluatecallback_options">#</a></span></h4> 934<div class="api_metadata"> 935<span>Added in: v13.0.0, v12.16.0</span> 936</div> 937<ul> 938<li><code>exportNames</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> Array of names that will be exported from the module.</li> 939<li><code>evaluateCallback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called when the module is evaluated.</li> 940<li><code>options</code> 941<ul> 942<li><code>identifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> String used in stack traces.</li> 943</ul> 944<strong>Default:</strong> <code>'vm:module(i)'</code> where <code>i</code> is a context-specific ascending 945index. 946<ul> 947<li><code>context</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> object as returned by the 948<code>vm.createContext()</code> method, to compile and evaluate this <code>Module</code> in.</li> 949</ul> 950</li> 951</ul> 952<p>Creates a new <code>SyntheticModule</code> instance.</p> 953<p>Objects assigned to the exports of this instance may allow importers of 954the module to access information outside the specified <code>context</code>. Use 955<code>vm.runInContext()</code> to create objects in a specific context.</p> 956<h4><code>syntheticModule.setExport(name, value)</code><span><a class="mark" href="#vm_syntheticmodule_setexport_name_value" id="vm_syntheticmodule_setexport_name_value">#</a></span></h4> 957<div class="api_metadata"> 958<span>Added in: v13.0.0, v12.16.0</span> 959</div> 960<ul> 961<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Name of the export to set.</li> 962<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The value to set the export to.</li> 963</ul> 964<p>This method is used after the module is linked to set the values of exports. If 965it is called before the module is linked, an <a href="errors.html#ERR_VM_MODULE_STATUS"><code>ERR_VM_MODULE_STATUS</code></a> error 966will be thrown.</p> 967 968<pre><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> vm <span class="hljs-keyword">from</span> <span class="hljs-string">'vm'</span>; 969 970<span class="hljs-keyword">const</span> m = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SyntheticModule</span>([<span class="hljs-string">'x'</span>], <span class="hljs-function">() =></span> { 971 m.<span class="hljs-title function_">setExport</span>(<span class="hljs-string">'x'</span>, <span class="hljs-number">1</span>); 972}); 973 974<span class="hljs-keyword">await</span> m.<span class="hljs-title function_">link</span>(<span class="hljs-function">() =></span> {}); 975<span class="hljs-keyword">await</span> m.evaluate(); 976 977assert.<span class="hljs-title function_">strictEqual</span>(m.<span class="hljs-property">namespace</span>.<span class="hljs-property">x</span>, <span class="hljs-number">1</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 978(<span class="hljs-keyword">async</span> () => { 979 <span class="hljs-keyword">const</span> m = <span class="hljs-keyword">new</span> vm.<span class="hljs-title class_">SyntheticModule</span>([<span class="hljs-string">'x'</span>], <span class="hljs-function">() =></span> { 980 m.<span class="hljs-title function_">setExport</span>(<span class="hljs-string">'x'</span>, <span class="hljs-number">1</span>); 981 }); 982 <span class="hljs-keyword">await</span> m.<span class="hljs-title function_">link</span>(<span class="hljs-function">() =></span> {}); 983 <span class="hljs-keyword">await</span> m.evaluate(); 984 assert.<span class="hljs-title function_">strictEqual</span>(m.<span class="hljs-property">namespace</span>.<span class="hljs-property">x</span>, <span class="hljs-number">1</span>); 985})();</code></pre> 986</section><section><h3><code>vm.compileFunction(code[, params[, options]])</code><span><a class="mark" href="#vm_vm_compilefunction_code_params_options" id="vm_vm_compilefunction_code_params_options">#</a></span></h3> 987<div class="api_metadata"> 988<details class="changelog"><summary>History</summary> 989<table> 990<tbody><tr><th>Version</th><th>Changes</th></tr> 991<tr><td>v14.3.0</td> 992<td><p>Removal of <code>importModuleDynamically</code> due to compatibility issues.</p></td></tr> 993<tr><td>v14.1.0, v13.14.0</td> 994<td><p>The <code>importModuleDynamically</code> option is now supported.</p></td></tr> 995<tr><td>v10.10.0</td> 996<td><p><span>Added in: v10.10.0</span></p></td></tr> 997</tbody></table> 998</details> 999</div> 1000<ul> 1001<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The body of the function to compile.</li> 1002<li><code>params</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> An array of strings containing all parameters for the 1003function.</li> 1004<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1005<ul> 1006<li><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Specifies the filename used in stack traces produced 1007by this script. <strong>Default:</strong> <code>''</code>.</li> 1008<li><code>lineOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the line number offset that is displayed 1009in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1010<li><code>columnOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the first-line column number offset that 1011is displayed in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1012<li><code>cachedData</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> Provides an optional <code>Buffer</code> or 1013<code>TypedArray</code>, or <code>DataView</code> with V8's code cache data for the supplied 1014source.</li> 1015<li><code>produceCachedData</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Specifies whether to produce new cache data. 1016<strong>Default:</strong> <code>false</code>.</li> 1017<li><code>parsingContext</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> object in which the said 1018function should be compiled in.</li> 1019<li><code>contextExtensions</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a> An array containing a collection of context 1020extensions (objects wrapping the current scope) to be applied while 1021compiling. <strong>Default:</strong> <code>[]</code>.</li> 1022</ul> 1023</li> 1024<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1025</ul> 1026<p>Compiles the given code into the provided context (if no context is 1027supplied, the current context is used), and returns it wrapped inside a 1028function with the given <code>params</code>.</p> 1029</section><section><h3><code>vm.createContext([contextObject[, options]])</code><span><a class="mark" href="#vm_vm_createcontext_contextobject_options" id="vm_vm_createcontext_contextobject_options">#</a></span></h3> 1030<div class="api_metadata"> 1031<details class="changelog"><summary>History</summary> 1032<table> 1033<tbody><tr><th>Version</th><th>Changes</th></tr> 1034<tr><td>v14.6.0</td> 1035<td><p>The <code>microtaskMode</code> option is supported now.</p></td></tr> 1036<tr><td>v10.0.0</td> 1037<td><p>The first argument can no longer be a function.</p></td></tr> 1038<tr><td>v10.0.0</td> 1039<td><p>The <code>codeGeneration</code> option is supported now.</p></td></tr> 1040<tr><td>v0.3.1</td> 1041<td><p><span>Added in: v0.3.1</span></p></td></tr> 1042</tbody></table> 1043</details> 1044</div> 1045<ul> 1046<li><code>contextObject</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1047<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1048<ul> 1049<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Human-readable name of the newly created context. 1050<strong>Default:</strong> <code>'VM Context i'</code>, where <code>i</code> is an ascending numerical index of 1051the created context.</li> 1052<li><code>origin</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <a href="https://developer.mozilla.org/en-US/docs/Glossary/Origin">Origin</a> corresponding to the newly created 1053context for display purposes. The origin should be formatted like a URL, 1054but with only the scheme, host, and port (if necessary), like the value of 1055the <a href="url.html#url_url_origin"><code>url.origin</code></a> property of a <a href="url.html#url_class_url"><code>URL</code></a> object. Most notably, this 1056string should omit the trailing slash, as that denotes a path. 1057<strong>Default:</strong> <code>''</code>.</li> 1058<li><code>codeGeneration</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1059<ul> 1060<li><code>strings</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to false any calls to <code>eval</code> or function 1061constructors (<code>Function</code>, <code>GeneratorFunction</code>, etc) will throw an 1062<code>EvalError</code>. <strong>Default:</strong> <code>true</code>.</li> 1063<li><code>wasm</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to false any attempt to compile a WebAssembly 1064module will throw a <code>WebAssembly.CompileError</code>. <strong>Default:</strong> <code>true</code>.</li> 1065</ul> 1066</li> 1067<li><code>microtaskMode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If set to <code>afterEvaluate</code>, microtasks (tasks 1068scheduled through <code>Promise</code>s and <code>async function</code>s) will be run immediately 1069after a script has run through <a href="#vm_script_runincontext_contextifiedobject_options"><code>script.runInContext()</code></a>. 1070They are included in the <code>timeout</code> and <code>breakOnSigint</code> scopes in that case.</li> 1071</ul> 1072</li> 1073<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> contextified object.</li> 1074</ul> 1075<p>If given a <code>contextObject</code>, the <code>vm.createContext()</code> method will <a href="#vm_what_does_it_mean_to_contextify_an_object">prepare 1076that object</a> so that it can be used in calls to 1077<a href="#vm_vm_runincontext_code_contextifiedobject_options"><code>vm.runInContext()</code></a> or <a href="#vm_script_runincontext_contextifiedobject_options"><code>script.runInContext()</code></a>. Inside such scripts, 1078the <code>contextObject</code> will be the global object, retaining all of its existing 1079properties but also having the built-in objects and functions any standard 1080<a href="https://es5.github.io/#x15.1">global object</a> has. Outside of scripts run by the vm module, global variables 1081will remain unchanged.</p> 1082<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1083 1084<span class="hljs-variable language_">global</span>.<span class="hljs-property">globalVar</span> = <span class="hljs-number">3</span>; 1085 1086<span class="hljs-keyword">const</span> context = { <span class="hljs-attr">globalVar</span>: <span class="hljs-number">1</span> }; 1087vm.<span class="hljs-title function_">createContext</span>(context); 1088 1089vm.<span class="hljs-title function_">runInContext</span>(<span class="hljs-string">'globalVar *= 2;'</span>, context); 1090 1091<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(context); 1092<span class="hljs-comment">// Prints: { globalVar: 2 }</span> 1093 1094<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-variable language_">global</span>.<span class="hljs-property">globalVar</span>); 1095<span class="hljs-comment">// Prints: 3</span></code></pre> 1096<p>If <code>contextObject</code> is omitted (or passed explicitly as <code>undefined</code>), a new, 1097empty <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> object will be returned.</p> 1098<p>The <code>vm.createContext()</code> method is primarily useful for creating a single 1099context that can be used to run multiple scripts. For instance, if emulating a 1100web browser, the method can be used to create a single context representing a 1101window's global object, then run all <code><script></code> tags together within that 1102context.</p> 1103<p>The provided <code>name</code> and <code>origin</code> of the context are made visible through the 1104Inspector API.</p> 1105</section><section><h3><code>vm.isContext(object)</code><span><a class="mark" href="#vm_vm_iscontext_object" id="vm_vm_iscontext_object">#</a></span></h3> 1106<div class="api_metadata"> 1107<span>Added in: v0.11.7</span> 1108</div> 1109<ul> 1110<li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1111<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1112</ul> 1113<p>Returns <code>true</code> if the given <code>object</code> object has been <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> using 1114<a href="#vm_vm_createcontext_contextobject_options"><code>vm.createContext()</code></a>.</p> 1115</section><section><h3><code>vm.measureMemory([options])</code><span><a class="mark" href="#vm_vm_measurememory_options" id="vm_vm_measurememory_options">#</a></span></h3> 1116<div class="api_metadata"> 1117<span>Added in: v13.10.0</span> 1118</div> 1119<p></p><div class="api_stability api_stability_1"><a href="documentation.html#documentation_stability_index">Stability: 1</a> - Experimental</div><p></p> 1120<p>Measure the memory known to V8 and used by all contexts known to the 1121current V8 isolate, or the main context.</p> 1122<ul> 1123<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Optional. 1124<ul> 1125<li><code>mode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'summary'</code> or <code>'detailed'</code>. In summary mode, 1126only the memory measured for the main context will be returned. In 1127detailed mode, the measure measured for all contexts known to the 1128current V8 isolate will be returned. 1129<strong>Default:</strong> <code>'summary'</code></li> 1130<li><code>execution</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'default'</code> or <code>'eager'</code>. With default 1131execution, the promise will not resolve until after the next scheduled 1132garbage collection starts, which may take a while (or never if the program 1133exits before the next GC). With eager execution, the GC will be started 1134right away to measure the memory. 1135<strong>Default:</strong> <code>'default'</code></li> 1136</ul> 1137</li> 1138<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> If the memory is successfully measured the promise will 1139resolve with an object containing information about the memory usage.</li> 1140</ul> 1141<p>The format of the object that the returned Promise may resolve with is 1142specific to the V8 engine and may change from one version of V8 to the next.</p> 1143<p>The returned result is different from the statistics returned by 1144<code>v8.getHeapSpaceStatistics()</code> in that <code>vm.measureMemory()</code> measure the 1145memory reachable by each V8 specific contexts in the current instance of 1146the V8 engine, while the result of <code>v8.getHeapSpaceStatistics()</code> measure 1147the memory occupied by each heap space in the current V8 instance.</p> 1148<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1149<span class="hljs-comment">// Measure the memory used by the main context.</span> 1150vm.<span class="hljs-title function_">measureMemory</span>({ <span class="hljs-attr">mode</span>: <span class="hljs-string">'summary'</span> }) 1151 <span class="hljs-comment">// This is the same as vm.measureMemory()</span> 1152 .<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1153 <span class="hljs-comment">// The current format is:</span> 1154 <span class="hljs-comment">// {</span> 1155 <span class="hljs-comment">// total: {</span> 1156 <span class="hljs-comment">// jsMemoryEstimate: 2418479, jsMemoryRange: [ 2418479, 2745799 ]</span> 1157 <span class="hljs-comment">// }</span> 1158 <span class="hljs-comment">// }</span> 1159 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(result); 1160 }); 1161 1162<span class="hljs-keyword">const</span> context = vm.<span class="hljs-title function_">createContext</span>({ <span class="hljs-attr">a</span>: <span class="hljs-number">1</span> }); 1163vm.<span class="hljs-title function_">measureMemory</span>({ <span class="hljs-attr">mode</span>: <span class="hljs-string">'detailed'</span>, <span class="hljs-attr">execution</span>: <span class="hljs-string">'eager'</span> }) 1164 .<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1165 <span class="hljs-comment">// Reference the context here so that it won't be GC'ed</span> 1166 <span class="hljs-comment">// until the measurement is complete.</span> 1167 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(context.<span class="hljs-property">a</span>); 1168 <span class="hljs-comment">// {</span> 1169 <span class="hljs-comment">// total: {</span> 1170 <span class="hljs-comment">// jsMemoryEstimate: 2574732,</span> 1171 <span class="hljs-comment">// jsMemoryRange: [ 2574732, 2904372 ]</span> 1172 <span class="hljs-comment">// },</span> 1173 <span class="hljs-comment">// current: {</span> 1174 <span class="hljs-comment">// jsMemoryEstimate: 2438996,</span> 1175 <span class="hljs-comment">// jsMemoryRange: [ 2438996, 2768636 ]</span> 1176 <span class="hljs-comment">// },</span> 1177 <span class="hljs-comment">// other: [</span> 1178 <span class="hljs-comment">// {</span> 1179 <span class="hljs-comment">// jsMemoryEstimate: 135736,</span> 1180 <span class="hljs-comment">// jsMemoryRange: [ 135736, 465376 ]</span> 1181 <span class="hljs-comment">// }</span> 1182 <span class="hljs-comment">// ]</span> 1183 <span class="hljs-comment">// }</span> 1184 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(result); 1185 });</code></pre> 1186</section><section><h3><code>vm.runInContext(code, contextifiedObject[, options])</code><span><a class="mark" href="#vm_vm_runincontext_code_contextifiedobject_options" id="vm_vm_runincontext_code_contextifiedobject_options">#</a></span></h3> 1187<div class="api_metadata"> 1188<details class="changelog"><summary>History</summary> 1189<table> 1190<tbody><tr><th>Version</th><th>Changes</th></tr> 1191<tr><td>v6.3.0</td> 1192<td><p>The <code>breakOnSigint</code> option is supported now.</p></td></tr> 1193<tr><td>v0.3.1</td> 1194<td><p><span>Added in: v0.3.1</span></p></td></tr> 1195</tbody></table> 1196</details> 1197</div> 1198<ul> 1199<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The JavaScript code to compile and run.</li> 1200<li><code>contextifiedObject</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> object that will be used 1201as the <code>global</code> when the <code>code</code> is compiled and run.</li> 1202<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> 1203<ul> 1204<li><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Specifies the filename used in stack traces produced 1205by this script. <strong>Default:</strong> <code>'evalmachine.<anonymous>'</code>.</li> 1206<li><code>lineOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the line number offset that is displayed 1207in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1208<li><code>columnOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the first-line column number offset that 1209is displayed in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1210<li><code>displayErrors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, if an <a href="errors.html#errors_class_error"><code>Error</code></a> occurs 1211while compiling the <code>code</code>, the line of code causing the error is attached 1212to the stack trace. <strong>Default:</strong> <code>true</code>.</li> 1213<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the number of milliseconds to execute <code>code</code> 1214before terminating execution. If execution is terminated, an <a href="errors.html#errors_class_error"><code>Error</code></a> 1215will be thrown. This value must be a strictly positive integer.</li> 1216<li><code>breakOnSigint</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, receiving <code>SIGINT</code> 1217(<kbd>Ctrl</kbd>+<kbd>C</kbd>) will terminate execution and throw an 1218<a href="errors.html#errors_class_error"><code>Error</code></a>. Existing handlers for the event that have been attached via 1219<code>process.on('SIGINT')</code> are disabled during script execution, but continue to 1220work after that. <strong>Default:</strong> <code>false</code>.</li> 1221<li><code>cachedData</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> Provides an optional <code>Buffer</code> or 1222<code>TypedArray</code>, or <code>DataView</code> with V8's code cache data for the supplied 1223source. When supplied, the <code>cachedDataRejected</code> value will be set to 1224either <code>true</code> or <code>false</code> depending on acceptance of the data by V8.</li> 1225<li><code>produceCachedData</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code> and no <code>cachedData</code> is present, V8 1226will attempt to produce code cache data for <code>code</code>. Upon success, a 1227<code>Buffer</code> with V8's code cache data will be produced and stored in the 1228<code>cachedData</code> property of the returned <code>vm.Script</code> instance. 1229The <code>cachedDataProduced</code> value will be set to either <code>true</code> or <code>false</code> 1230depending on whether code cache data is produced successfully. 1231This option is <strong>deprecated</strong> in favor of <code>script.createCachedData()</code>. 1232<strong>Default:</strong> <code>false</code>.</li> 1233<li><code>importModuleDynamically</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called during evaluation of this module 1234when <code>import()</code> is called. If this option is not specified, calls to 1235<code>import()</code> will reject with <a href="errors.html#ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING"><code>ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING</code></a>. 1236This option is part of the experimental modules API. We do not recommend 1237using it in a production environment. 1238<ul> 1239<li><code>specifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> specifier passed to <code>import()</code></li> 1240<li><code>script</code> <a href="vm.html#vm_class_vm_script" class="type"><vm.Script></a></li> 1241<li>Returns: <a href="https://tc39.github.io/ecma262/#sec-module-namespace-exotic-objects" class="type"><Module Namespace Object></a> | <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a> Returning a <code>vm.Module</code> is 1242recommended in order to take advantage of error tracking, and to avoid 1243issues with namespaces that contain <code>then</code> function exports.</li> 1244</ul> 1245</li> 1246</ul> 1247</li> 1248<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the result of the very last statement executed in the script.</li> 1249</ul> 1250<p>The <code>vm.runInContext()</code> method compiles <code>code</code>, runs it within the context of 1251the <code>contextifiedObject</code>, then returns the result. Running code does not have 1252access to the local scope. The <code>contextifiedObject</code> object <em>must</em> have been 1253previously <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> using the <a href="#vm_vm_createcontext_contextobject_options"><code>vm.createContext()</code></a> method.</p> 1254<p>If <code>options</code> is a string, then it specifies the filename.</p> 1255<p>The following example compiles and executes different scripts using a single 1256<a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a> object:</p> 1257<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1258 1259<span class="hljs-keyword">const</span> contextObject = { <span class="hljs-attr">globalVar</span>: <span class="hljs-number">1</span> }; 1260vm.<span class="hljs-title function_">createContext</span>(contextObject); 1261 1262<span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> i = <span class="hljs-number">0</span>; i < <span class="hljs-number">10</span>; ++i) { 1263 vm.<span class="hljs-title function_">runInContext</span>(<span class="hljs-string">'globalVar *= 2;'</span>, contextObject); 1264} 1265<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(contextObject); 1266<span class="hljs-comment">// Prints: { globalVar: 1024 }</span></code></pre> 1267</section><section><h3><code>vm.runInNewContext(code[, contextObject[, options]])</code><span><a class="mark" href="#vm_vm_runinnewcontext_code_contextobject_options" id="vm_vm_runinnewcontext_code_contextobject_options">#</a></span></h3> 1268<div class="api_metadata"> 1269<details class="changelog"><summary>History</summary> 1270<table> 1271<tbody><tr><th>Version</th><th>Changes</th></tr> 1272<tr><td>v14.6.0</td> 1273<td><p>The <code>microtaskMode</code> option is supported now.</p></td></tr> 1274<tr><td>v10.0.0</td> 1275<td><p>The <code>contextCodeGeneration</code> option is supported now.</p></td></tr> 1276<tr><td>v6.3.0</td> 1277<td><p>The <code>breakOnSigint</code> option is supported now.</p></td></tr> 1278<tr><td>v0.3.1</td> 1279<td><p><span>Added in: v0.3.1</span></p></td></tr> 1280</tbody></table> 1281</details> 1282</div> 1283<ul> 1284<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The JavaScript code to compile and run.</li> 1285<li><code>contextObject</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> An object that will be <a href="#vm_what_does_it_mean_to_contextify_an_object">contextified</a>. If 1286<code>undefined</code>, a new object will be created.</li> 1287<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> 1288<ul> 1289<li><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Specifies the filename used in stack traces produced 1290by this script. <strong>Default:</strong> <code>'evalmachine.<anonymous>'</code>.</li> 1291<li><code>lineOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the line number offset that is displayed 1292in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1293<li><code>columnOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the first-line column number offset that 1294is displayed in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1295<li><code>displayErrors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, if an <a href="errors.html#errors_class_error"><code>Error</code></a> occurs 1296while compiling the <code>code</code>, the line of code causing the error is attached 1297to the stack trace. <strong>Default:</strong> <code>true</code>.</li> 1298<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the number of milliseconds to execute <code>code</code> 1299before terminating execution. If execution is terminated, an <a href="errors.html#errors_class_error"><code>Error</code></a> 1300will be thrown. This value must be a strictly positive integer.</li> 1301<li><code>breakOnSigint</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, receiving <code>SIGINT</code> 1302(<kbd>Ctrl</kbd>+<kbd>C</kbd>) will terminate execution and throw an 1303<a href="errors.html#errors_class_error"><code>Error</code></a>. Existing handlers for the event that have been attached via 1304<code>process.on('SIGINT')</code> are disabled during script execution, but continue to 1305work after that. <strong>Default:</strong> <code>false</code>.</li> 1306<li><code>contextName</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Human-readable name of the newly created context. 1307<strong>Default:</strong> <code>'VM Context i'</code>, where <code>i</code> is an ascending numerical index of 1308the created context.</li> 1309<li><code>contextOrigin</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <a href="https://developer.mozilla.org/en-US/docs/Glossary/Origin">Origin</a> corresponding to the newly 1310created context for display purposes. The origin should be formatted like a 1311URL, but with only the scheme, host, and port (if necessary), like the 1312value of the <a href="url.html#url_url_origin"><code>url.origin</code></a> property of a <a href="url.html#url_class_url"><code>URL</code></a> object. Most notably, 1313this string should omit the trailing slash, as that denotes a path. 1314<strong>Default:</strong> <code>''</code>.</li> 1315<li><code>contextCodeGeneration</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1316<ul> 1317<li><code>strings</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to false any calls to <code>eval</code> or function 1318constructors (<code>Function</code>, <code>GeneratorFunction</code>, etc) will throw an 1319<code>EvalError</code>. <strong>Default:</strong> <code>true</code>.</li> 1320<li><code>wasm</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If set to false any attempt to compile a WebAssembly 1321module will throw a <code>WebAssembly.CompileError</code>. <strong>Default:</strong> <code>true</code>.</li> 1322</ul> 1323</li> 1324<li><code>cachedData</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> Provides an optional <code>Buffer</code> or 1325<code>TypedArray</code>, or <code>DataView</code> with V8's code cache data for the supplied 1326source. When supplied, the <code>cachedDataRejected</code> value will be set to 1327either <code>true</code> or <code>false</code> depending on acceptance of the data by V8.</li> 1328<li><code>produceCachedData</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code> and no <code>cachedData</code> is present, V8 1329will attempt to produce code cache data for <code>code</code>. Upon success, a 1330<code>Buffer</code> with V8's code cache data will be produced and stored in the 1331<code>cachedData</code> property of the returned <code>vm.Script</code> instance. 1332The <code>cachedDataProduced</code> value will be set to either <code>true</code> or <code>false</code> 1333depending on whether code cache data is produced successfully. 1334This option is <strong>deprecated</strong> in favor of <code>script.createCachedData()</code>. 1335<strong>Default:</strong> <code>false</code>.</li> 1336<li><code>importModuleDynamically</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called during evaluation of this module 1337when <code>import()</code> is called. If this option is not specified, calls to 1338<code>import()</code> will reject with <a href="errors.html#ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING"><code>ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING</code></a>. 1339This option is part of the experimental modules API. We do not recommend 1340using it in a production environment. 1341<ul> 1342<li><code>specifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> specifier passed to <code>import()</code></li> 1343<li><code>script</code> <a href="vm.html#vm_class_vm_script" class="type"><vm.Script></a></li> 1344<li>Returns: <a href="https://tc39.github.io/ecma262/#sec-module-namespace-exotic-objects" class="type"><Module Namespace Object></a> | <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a> Returning a <code>vm.Module</code> is 1345recommended in order to take advantage of error tracking, and to avoid 1346issues with namespaces that contain <code>then</code> function exports.</li> 1347</ul> 1348</li> 1349<li><code>microtaskMode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If set to <code>afterEvaluate</code>, microtasks (tasks 1350scheduled through <code>Promise</code>s and <code>async function</code>s) will be run immediately 1351after the script has run. They are included in the <code>timeout</code> and 1352<code>breakOnSigint</code> scopes in that case.</li> 1353</ul> 1354</li> 1355<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the result of the very last statement executed in the script.</li> 1356</ul> 1357<p>The <code>vm.runInNewContext()</code> first contextifies the given <code>contextObject</code> (or 1358creates a new <code>contextObject</code> if passed as <code>undefined</code>), compiles the <code>code</code>, 1359runs it within the created context, then returns the result. Running code 1360does not have access to the local scope.</p> 1361<p>If <code>options</code> is a string, then it specifies the filename.</p> 1362<p>The following example compiles and executes code that increments a global 1363variable and sets a new one. These globals are contained in the <code>contextObject</code>.</p> 1364<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1365 1366<span class="hljs-keyword">const</span> contextObject = { 1367 <span class="hljs-attr">animal</span>: <span class="hljs-string">'cat'</span>, 1368 <span class="hljs-attr">count</span>: <span class="hljs-number">2</span> 1369}; 1370 1371vm.<span class="hljs-title function_">runInNewContext</span>(<span class="hljs-string">'count += 1; name = "kitty"'</span>, contextObject); 1372<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(contextObject); 1373<span class="hljs-comment">// Prints: { animal: 'cat', count: 3, name: 'kitty' }</span></code></pre> 1374</section><section><h3><code>vm.runInThisContext(code[, options])</code><span><a class="mark" href="#vm_vm_runinthiscontext_code_options" id="vm_vm_runinthiscontext_code_options">#</a></span></h3> 1375<div class="api_metadata"> 1376<details class="changelog"><summary>History</summary> 1377<table> 1378<tbody><tr><th>Version</th><th>Changes</th></tr> 1379<tr><td>v6.3.0</td> 1380<td><p>The <code>breakOnSigint</code> option is supported now.</p></td></tr> 1381<tr><td>v0.3.1</td> 1382<td><p><span>Added in: v0.3.1</span></p></td></tr> 1383</tbody></table> 1384</details> 1385</div> 1386<ul> 1387<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The JavaScript code to compile and run.</li> 1388<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> 1389<ul> 1390<li><code>filename</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Specifies the filename used in stack traces produced 1391by this script. <strong>Default:</strong> <code>'evalmachine.<anonymous>'</code>.</li> 1392<li><code>lineOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the line number offset that is displayed 1393in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1394<li><code>columnOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Specifies the first-line column number offset that 1395is displayed in stack traces produced by this script. <strong>Default:</strong> <code>0</code>.</li> 1396<li><code>displayErrors</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, if an <a href="errors.html#errors_class_error"><code>Error</code></a> occurs 1397while compiling the <code>code</code>, the line of code causing the error is attached 1398to the stack trace. <strong>Default:</strong> <code>true</code>.</li> 1399<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Specifies the number of milliseconds to execute <code>code</code> 1400before terminating execution. If execution is terminated, an <a href="errors.html#errors_class_error"><code>Error</code></a> 1401will be thrown. This value must be a strictly positive integer.</li> 1402<li><code>breakOnSigint</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If <code>true</code>, receiving <code>SIGINT</code> 1403(<kbd>Ctrl</kbd>+<kbd>C</kbd>) will terminate execution and throw an 1404<a href="errors.html#errors_class_error"><code>Error</code></a>. Existing handlers for the event that have been attached via 1405<code>process.on('SIGINT')</code> are disabled during script execution, but continue to 1406work after that. <strong>Default:</strong> <code>false</code>.</li> 1407<li><code>cachedData</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> Provides an optional <code>Buffer</code> or 1408<code>TypedArray</code>, or <code>DataView</code> with V8's code cache data for the supplied 1409source. When supplied, the <code>cachedDataRejected</code> value will be set to 1410either <code>true</code> or <code>false</code> depending on acceptance of the data by V8.</li> 1411<li><code>produceCachedData</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code> and no <code>cachedData</code> is present, V8 1412will attempt to produce code cache data for <code>code</code>. Upon success, a 1413<code>Buffer</code> with V8's code cache data will be produced and stored in the 1414<code>cachedData</code> property of the returned <code>vm.Script</code> instance. 1415The <code>cachedDataProduced</code> value will be set to either <code>true</code> or <code>false</code> 1416depending on whether code cache data is produced successfully. 1417This option is <strong>deprecated</strong> in favor of <code>script.createCachedData()</code>. 1418<strong>Default:</strong> <code>false</code>.</li> 1419<li><code>importModuleDynamically</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called during evaluation of this module 1420when <code>import()</code> is called. If this option is not specified, calls to 1421<code>import()</code> will reject with <a href="errors.html#ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING"><code>ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING</code></a>. 1422This option is part of the experimental modules API. We do not recommend 1423using it in a production environment. 1424<ul> 1425<li><code>specifier</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> specifier passed to <code>import()</code></li> 1426<li><code>script</code> <a href="vm.html#vm_class_vm_script" class="type"><vm.Script></a></li> 1427<li>Returns: <a href="https://tc39.github.io/ecma262/#sec-module-namespace-exotic-objects" class="type"><Module Namespace Object></a> | <a href="vm.html#vm_class_vm_module" class="type"><vm.Module></a> Returning a <code>vm.Module</code> is 1428recommended in order to take advantage of error tracking, and to avoid 1429issues with namespaces that contain <code>then</code> function exports.</li> 1430</ul> 1431</li> 1432</ul> 1433</li> 1434<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the result of the very last statement executed in the script.</li> 1435</ul> 1436<p><code>vm.runInThisContext()</code> compiles <code>code</code>, runs it within the context of the 1437current <code>global</code> and returns the result. Running code does not have access to 1438local scope, but does have access to the current <code>global</code> object.</p> 1439<p>If <code>options</code> is a string, then it specifies the filename.</p> 1440<p>The following example illustrates using both <code>vm.runInThisContext()</code> and 1441the JavaScript <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval"><code>eval()</code></a> function to run the same code:</p> 1442<!-- eslint-disable prefer-const --> 1443<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1444<span class="hljs-keyword">let</span> localVar = <span class="hljs-string">'initial value'</span>; 1445 1446<span class="hljs-keyword">const</span> vmResult = vm.<span class="hljs-title function_">runInThisContext</span>(<span class="hljs-string">'localVar = "vm";'</span>); 1447<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`vmResult: '<span class="hljs-subst">${vmResult}</span>', localVar: '<span class="hljs-subst">${localVar}</span>'`</span>); 1448<span class="hljs-comment">// Prints: vmResult: 'vm', localVar: 'initial value'</span> 1449 1450<span class="hljs-keyword">const</span> evalResult = <span class="hljs-built_in">eval</span>(<span class="hljs-string">'localVar = "eval";'</span>); 1451<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`evalResult: '<span class="hljs-subst">${evalResult}</span>', localVar: '<span class="hljs-subst">${localVar}</span>'`</span>); 1452<span class="hljs-comment">// Prints: evalResult: 'eval', localVar: 'eval'</span></code></pre> 1453<p>Because <code>vm.runInThisContext()</code> does not have access to the local scope, 1454<code>localVar</code> is unchanged. In contrast, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval"><code>eval()</code></a> <em>does</em> have access to the 1455local scope, so the value <code>localVar</code> is changed. In this way 1456<code>vm.runInThisContext()</code> is much like an <a href="https://es5.github.io/#x10.4.2">indirect <code>eval()</code> call</a>, e.g. 1457<code>(0,eval)('code')</code>.</p> 1458</section><section><h3>Example: Running an HTTP server within a VM<span><a class="mark" href="#vm_example_running_an_http_server_within_a_vm" id="vm_example_running_an_http_server_within_a_vm">#</a></span></h3> 1459<p>When using either <a href="#vm_script_runinthiscontext_options"><code>script.runInThisContext()</code></a> or 1460<a href="#vm_vm_runinthiscontext_code_options"><code>vm.runInThisContext()</code></a>, the code is executed within the current V8 global 1461context. The code passed to this VM context will have its own isolated scope.</p> 1462<p>In order to run a simple web server using the <code>http</code> module the code passed to 1463the context must either call <code>require('http')</code> on its own, or have a reference 1464to the <code>http</code> module passed to it. For instance:</p> 1465<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 1466<span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1467 1468<span class="hljs-keyword">const</span> code = <span class="hljs-string">` 1469((require) => { 1470 const http = require('http'); 1471 1472 http.createServer((request, response) => { 1473 response.writeHead(200, { 'Content-Type': 'text/plain' }); 1474 response.end('Hello World\\n'); 1475 }).listen(8124); 1476 1477 console.log('Server running at http://127.0.0.1:8124/'); 1478})`</span>; 1479 1480vm.<span class="hljs-title function_">runInThisContext</span>(code)(<span class="hljs-built_in">require</span>);</code></pre> 1481<p>The <code>require()</code> in the above case shares the state with the context it is 1482passed from. This may introduce risks when untrusted code is executed, e.g. 1483altering objects in the context in unwanted ways.</p> 1484</section><section><h3>What does it mean to "contextify" an object?<span><a class="mark" href="#vm_what_does_it_mean_to_contextify_an_object" id="vm_what_does_it_mean_to_contextify_an_object">#</a></span></h3> 1485<p>All JavaScript executed within Node.js runs within the scope of a "context". 1486According to the <a href="https://v8.dev/docs/embed#contexts">V8 Embedder's Guide</a>:</p> 1487<blockquote> 1488<p>In V8, a context is an execution environment that allows separate, unrelated, 1489JavaScript applications to run in a single instance of V8. You must explicitly 1490specify the context in which you want any JavaScript code to be run.</p> 1491</blockquote> 1492<p>When the method <code>vm.createContext()</code> is called, the <code>contextObject</code> argument 1493(or a newly-created object if <code>contextObject</code> is <code>undefined</code>) is associated 1494internally with a new instance of a V8 Context. This V8 Context provides the 1495<code>code</code> run using the <code>vm</code> module's methods with an isolated global environment 1496within which it can operate. The process of creating the V8 Context and 1497associating it with the <code>contextObject</code> is what this document refers to as 1498"contextifying" the object.</p> 1499</section><section><h3>Timeout interactions with asynchronous tasks and Promises<span><a class="mark" href="#vm_timeout_interactions_with_asynchronous_tasks_and_promises" id="vm_timeout_interactions_with_asynchronous_tasks_and_promises">#</a></span></h3> 1500<p><code>Promise</code>s and <code>async function</code>s can schedule tasks run by the JavaScript 1501engine asynchronously. By default, these tasks are run after all JavaScript 1502functions on the current stack are done executing. 1503This allows escaping the functionality of the <code>timeout</code> and 1504<code>breakOnSigint</code> options.</p> 1505<p>For example, the following code executed by <code>vm.runInNewContext()</code> with a 1506timeout of 5 milliseconds schedules an infinite loop to run after a promise 1507resolves. The scheduled loop is never interrupted by the timeout:</p> 1508<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1509 1510<span class="hljs-keyword">function</span> <span class="hljs-title function_">loop</span>(<span class="hljs-params"></span>) { 1511 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'entering loop'</span>); 1512 <span class="hljs-keyword">while</span> (<span class="hljs-number">1</span>) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>()); 1513} 1514 1515vm.<span class="hljs-title function_">runInNewContext</span>( 1516 <span class="hljs-string">'Promise.resolve().then(() => loop());'</span>, 1517 { loop, <span class="hljs-variable language_">console</span> }, 1518 { <span class="hljs-attr">timeout</span>: <span class="hljs-number">5</span> } 1519); 1520<span class="hljs-comment">// This is printed *before* 'entering loop' (!)</span> 1521<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'done executing'</span>);</code></pre> 1522<p>This can be addressed by passing <code>microtaskMode: 'afterEvaluate'</code> to the code 1523that creates the <code>Context</code>:</p> 1524<pre><code class="language-js"><span class="hljs-keyword">const</span> vm = <span class="hljs-built_in">require</span>(<span class="hljs-string">'vm'</span>); 1525 1526<span class="hljs-keyword">function</span> <span class="hljs-title function_">loop</span>(<span class="hljs-params"></span>) { 1527 <span class="hljs-keyword">while</span> (<span class="hljs-number">1</span>) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title class_">Date</span>.<span class="hljs-title function_">now</span>()); 1528} 1529 1530vm.<span class="hljs-title function_">runInNewContext</span>( 1531 <span class="hljs-string">'Promise.resolve().then(() => loop());'</span>, 1532 { loop, <span class="hljs-variable language_">console</span> }, 1533 { <span class="hljs-attr">timeout</span>: <span class="hljs-number">5</span>, <span class="hljs-attr">microtaskMode</span>: <span class="hljs-string">'afterEvaluate'</span> } 1534);</code></pre> 1535<p>In this case, the microtask scheduled through <code>promise.then()</code> will be run 1536before returning from <code>vm.runInNewContext()</code>, and will be interrupted 1537by the <code>timeout</code> functionality. This applies only to code running in a 1538<code>vm.Context</code>, so e.g. <a href="#vm_vm_runinthiscontext_code_options"><code>vm.runInThisContext()</code></a> does not take this option.</p> 1539<p>Promise callbacks are entered into the microtask queue of the context in which 1540they were created. For example, if <code>() => loop()</code> is replaced with just <code>loop</code> 1541in the above example, then <code>loop</code> will be pushed into the global microtask 1542queue, because it is a function from the outer (main) context, and thus will 1543also be able to escape the timeout.</p> 1544<p>If asynchronous scheduling functions such as <code>process.nextTick()</code>, 1545<code>queueMicrotask()</code>, <code>setTimeout()</code>, <code>setImmediate()</code>, etc. are made available 1546inside a <code>vm.Context</code>, functions passed to them will be added to global queues, 1547which are shared by all contexts. Therefore, callbacks passed to those functions 1548are not controllable through the timeout either.</p></section> 1549 <!-- API END --> 1550 </div> 1551 </div> 1552 </div> 1553 <script> 1554 'use strict'; 1555 { 1556 const kCustomPreference = 'customDarkTheme'; 1557 const userSettings = sessionStorage.getItem(kCustomPreference); 1558 const themeToggleButton = document.getElementById('theme-toggle-btn'); 1559 if (userSettings === null && window.matchMedia) { 1560 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 1561 if ('onchange' in mq) { 1562 function mqChangeListener(e) { 1563 document.body.classList.toggle('dark-mode', e.matches); 1564 } 1565 mq.addEventListener('change', mqChangeListener); 1566 if (themeToggleButton) { 1567 themeToggleButton.addEventListener('click', function() { 1568 mq.removeEventListener('change', mqChangeListener); 1569 }, { once: true }); 1570 } 1571 } 1572 if (mq.matches) { 1573 document.body.classList.add('dark-mode'); 1574 } 1575 } else if (userSettings === 'true') { 1576 document.body.classList.add('dark-mode'); 1577 } 1578 if (themeToggleButton) { 1579 themeToggleButton.hidden = false; 1580 themeToggleButton.addEventListener('click', function() { 1581 sessionStorage.setItem( 1582 kCustomPreference, 1583 document.body.classList.toggle('dark-mode') 1584 ); 1585 }); 1586 } 1587 } 1588 </script> 1589</body> 1590</html> 1591