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href="#modules_cycles">Cycles</a></li> 157<li><a href="#modules_file_modules">File modules</a></li> 158<li><a href="#modules_folders_as_modules">Folders as modules</a></li> 159<li><a href="#modules_loading_from_node_modules_folders">Loading from <code>node_modules</code> folders</a></li> 160<li><a href="#modules_loading_from_the_global_folders">Loading from the global folders</a></li> 161<li><a href="#modules_the_module_wrapper">The module wrapper</a></li> 162<li><a href="#modules_the_module_scope">The module scope</a> 163<ul> 164<li><a href="#modules_dirname"><code>__dirname</code></a></li> 165<li><a href="#modules_filename"><code>__filename</code></a></li> 166<li><a href="#modules_exports"><code>exports</code></a></li> 167<li><a href="#modules_module"><code>module</code></a></li> 168<li><a href="#modules_require_id"><code>require(id)</code></a> 169<ul> 170<li><a href="#modules_require_cache"><code>require.cache</code></a></li> 171<li><span class="stability_0"><a href="#modules_require_extensions"><code>require.extensions</code></a></span></li> 172<li><a href="#modules_require_main"><code>require.main</code></a></li> 173<li><a href="#modules_require_resolve_request_options"><code>require.resolve(request[, options])</code></a> 174<ul> 175<li><a href="#modules_require_resolve_paths_request"><code>require.resolve.paths(request)</code></a></li> 176</ul> 177</li> 178</ul> 179</li> 180</ul> 181</li> 182<li><a href="#modules_the_module_object">The <code>module</code> object</a> 183<ul> 184<li><a href="#modules_module_children"><code>module.children</code></a></li> 185<li><a href="#modules_module_exports"><code>module.exports</code></a> 186<ul> 187<li><a href="#modules_exports_shortcut"><code>exports</code> shortcut</a></li> 188</ul> 189</li> 190<li><a href="#modules_module_filename"><code>module.filename</code></a></li> 191<li><a href="#modules_module_id"><code>module.id</code></a></li> 192<li><a href="#modules_module_ispreloading"><code>module.isPreloading</code></a></li> 193<li><a href="#modules_module_loaded"><code>module.loaded</code></a></li> 194<li><span class="stability_0"><a href="#modules_module_parent"><code>module.parent</code></a></span></li> 195<li><a href="#modules_module_path"><code>module.path</code></a></li> 196<li><a href="#modules_module_paths"><code>module.paths</code></a></li> 197<li><a href="#modules_module_require_id"><code>module.require(id)</code></a></li> 198</ul> 199</li> 200<li><a href="#modules_the_module_object_1">The <code>Module</code> object</a></li> 201<li><a href="#modules_source_map_v3_support">Source map v3 support</a></li> 202</ul> 203</li> 204</ul></details> 205 206 <div id="apicontent"> 207 <h2>Modules: CommonJS modules<span><a class="mark" href="#modules_modules_commonjs_modules" id="modules_modules_commonjs_modules">#</a></span></h2> 208 209<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 210 211<p>In the Node.js module system, each file is treated as a separate module. For 212example, consider a file named <code>foo.js</code>:</p> 213<pre><code class="language-js"><span class="hljs-keyword">const</span> circle = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./circle.js'</span>); 214<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`The area of a circle of radius 4 is <span class="hljs-subst">${circle.area(<span class="hljs-number">4</span>)}</span>`</span>);</code></pre> 215<p>On the first line, <code>foo.js</code> loads the module <code>circle.js</code> that is in the same 216directory as <code>foo.js</code>.</p> 217<p>Here are the contents of <code>circle.js</code>:</p> 218<pre><code class="language-js"><span class="hljs-keyword">const</span> { <span class="hljs-variable constant_">PI</span> } = <span class="hljs-title class_">Math</span>; 219 220<span class="hljs-built_in">exports</span>.<span class="hljs-property">area</span> = <span class="hljs-function">(<span class="hljs-params">r</span>) =></span> <span class="hljs-variable constant_">PI</span> * r ** <span class="hljs-number">2</span>; 221 222<span class="hljs-built_in">exports</span>.<span class="hljs-property">circumference</span> = <span class="hljs-function">(<span class="hljs-params">r</span>) =></span> <span class="hljs-number">2</span> * <span class="hljs-variable constant_">PI</span> * r;</code></pre> 223<p>The module <code>circle.js</code> has exported the functions <code>area()</code> and 224<code>circumference()</code>. Functions and objects are added to the root of a module 225by specifying additional properties on the special <code>exports</code> object.</p> 226<p>Variables local to the module will be private, because the module is wrapped 227in a function by Node.js (see <a href="#modules_the_module_wrapper">module wrapper</a>). 228In this example, the variable <code>PI</code> is private to <code>circle.js</code>.</p> 229<p>The <code>module.exports</code> property can be assigned a new value (such as a function 230or object).</p> 231<p>Below, <code>bar.js</code> makes use of the <code>square</code> module, which exports a Square class:</p> 232<pre><code class="language-js"><span class="hljs-keyword">const</span> <span class="hljs-title class_">Square</span> = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./square.js'</span>); 233<span class="hljs-keyword">const</span> mySquare = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Square</span>(<span class="hljs-number">2</span>); 234<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`The area of mySquare is <span class="hljs-subst">${mySquare.area()}</span>`</span>);</code></pre> 235<p>The <code>square</code> module is defined in <code>square.js</code>:</p> 236<pre><code class="language-js"><span class="hljs-comment">// Assigning to exports will not modify module, must use module.exports</span> 237<span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span> = <span class="hljs-keyword">class</span> <span class="hljs-title class_">Square</span> { 238 <span class="hljs-title function_">constructor</span>(<span class="hljs-params">width</span>) { 239 <span class="hljs-variable language_">this</span>.<span class="hljs-property">width</span> = width; 240 } 241 242 <span class="hljs-title function_">area</span>(<span class="hljs-params"></span>) { 243 <span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">width</span> ** <span class="hljs-number">2</span>; 244 } 245};</code></pre> 246<p>The module system is implemented in the <code>require('module')</code> module.</p> 247<section><h3>Accessing the main module<span><a class="mark" href="#modules_accessing_the_main_module" id="modules_accessing_the_main_module">#</a></span></h3> 248 249<p>When a file is run directly from Node.js, <code>require.main</code> is set to its 250<code>module</code>. That means that it is possible to determine whether a file has been 251run directly by testing <code>require.main === module</code>.</p> 252<p>For a file <code>foo.js</code>, this will be <code>true</code> if run via <code>node foo.js</code>, but 253<code>false</code> if run by <code>require('./foo')</code>.</p> 254<p>Because <code>module</code> provides a <code>filename</code> property (normally equivalent to 255<code>__filename</code>), the entry point of the current application can be obtained 256by checking <code>require.main.filename</code>.</p> 257</section><section><h3>Package manager tips<span><a class="mark" href="#modules_package_manager_tips" id="modules_package_manager_tips">#</a></span></h3> 258 259<p>The semantics of the Node.js <code>require()</code> function were designed to be general 260enough to support reasonable directory structures. Package manager programs 261such as <code>dpkg</code>, <code>rpm</code>, and <code>npm</code> will hopefully find it possible to build 262native packages from Node.js modules without modification.</p> 263<p>Below we give a suggested directory structure that could work:</p> 264<p>Let's say that we wanted to have the folder at 265<code>/usr/lib/node/<some-package>/<some-version></code> hold the contents of a 266specific version of a package.</p> 267<p>Packages can depend on one another. In order to install package <code>foo</code>, it 268may be necessary to install a specific version of package <code>bar</code>. The <code>bar</code> 269package may itself have dependencies, and in some cases, these may even collide 270or form cyclic dependencies.</p> 271<p>Because Node.js looks up the <code>realpath</code> of any modules it loads (that is, it 272resolves symlinks) and then <a href="#modules_loading_from_node_modules_folders">looks for their dependencies in <code>node_modules</code> folders</a>, 273this situation can be resolved with the following architecture:</p> 274<ul> 275<li><code>/usr/lib/node/foo/1.2.3/</code>: Contents of the <code>foo</code> package, version 1.2.3.</li> 276<li><code>/usr/lib/node/bar/4.3.2/</code>: Contents of the <code>bar</code> package that <code>foo</code> depends 277on.</li> 278<li><code>/usr/lib/node/foo/1.2.3/node_modules/bar</code>: Symbolic link to 279<code>/usr/lib/node/bar/4.3.2/</code>.</li> 280<li><code>/usr/lib/node/bar/4.3.2/node_modules/*</code>: Symbolic links to the packages that 281<code>bar</code> depends on.</li> 282</ul> 283<p>Thus, even if a cycle is encountered, or if there are dependency 284conflicts, every module will be able to get a version of its dependency 285that it can use.</p> 286<p>When the code in the <code>foo</code> package does <code>require('bar')</code>, it will get the 287version that is symlinked into <code>/usr/lib/node/foo/1.2.3/node_modules/bar</code>. 288Then, when the code in the <code>bar</code> package calls <code>require('quux')</code>, it'll get 289the version that is symlinked into 290<code>/usr/lib/node/bar/4.3.2/node_modules/quux</code>.</p> 291<p>Furthermore, to make the module lookup process even more optimal, rather 292than putting packages directly in <code>/usr/lib/node</code>, we could put them in 293<code>/usr/lib/node_modules/<name>/<version></code>. Then Node.js will not bother 294looking for missing dependencies in <code>/usr/node_modules</code> or <code>/node_modules</code>.</p> 295<p>In order to make modules available to the Node.js REPL, it might be useful to 296also add the <code>/usr/lib/node_modules</code> folder to the <code>$NODE_PATH</code> environment 297variable. Since the module lookups using <code>node_modules</code> folders are all 298relative, and based on the real path of the files making the calls to 299<code>require()</code>, the packages themselves can be anywhere.</p> 300</section><section><h3>The <code>.mjs</code> extension<span><a class="mark" href="#modules_the_mjs_extension" id="modules_the_mjs_extension">#</a></span></h3> 301<p>It is not possible to <code>require()</code> files that have the <code>.mjs</code> extension. 302Attempting to do so will throw <a href="errors.html#errors_err_require_esm">an error</a>. The <code>.mjs</code> extension is 303reserved for <a href="esm.html">ECMAScript Modules</a> which cannot be loaded via <code>require()</code>. 304See <a href="esm.html">ECMAScript Modules</a> for more details.</p> 305</section><section><h3>All together...<span><a class="mark" href="#modules_all_together" id="modules_all_together">#</a></span></h3> 306 307<p>To get the exact filename that will be loaded when <code>require()</code> is called, use 308the <code>require.resolve()</code> function.</p> 309<p>Putting together all of the above, here is the high-level algorithm 310in pseudocode of what <code>require()</code> does:</p> 311<pre>require(X) from module at path Y 3121. If X is a core module, 313 a. return the core module 314 b. STOP 3152. If X begins with '/' 316 a. set Y to be the filesystem root 3173. If X begins with './' or '/' or '../' 318 a. LOAD_AS_FILE(Y + X) 319 b. LOAD_AS_DIRECTORY(Y + X) 320 c. THROW "not found" 3214. If X begins with '#' 322 a. LOAD_PACKAGE_IMPORTS(X, dirname(Y)) 3235. LOAD_PACKAGE_SELF(X, dirname(Y)) 3246. LOAD_NODE_MODULES(X, dirname(Y)) 3257. THROW "not found" 326 327LOAD_AS_FILE(X) 3281. If X is a file, load X as its file extension format. STOP 3292. If X.js is a file, load X.js as JavaScript text. STOP 3303. If X.json is a file, parse X.json to a JavaScript Object. STOP 3314. If X.node is a file, load X.node as binary addon. STOP 332 333LOAD_INDEX(X) 3341. If X/index.js is a file, load X/index.js as JavaScript text. STOP 3352. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP 3363. If X/index.node is a file, load X/index.node as binary addon. STOP 337 338LOAD_AS_DIRECTORY(X) 3391. If X/package.json is a file, 340 a. Parse X/package.json, and look for "main" field. 341 b. If "main" is a falsy value, GOTO 2. 342 c. let M = X + (json main field) 343 d. LOAD_AS_FILE(M) 344 e. LOAD_INDEX(M) 345 f. LOAD_INDEX(X) DEPRECATED 346 g. THROW "not found" 3472. LOAD_INDEX(X) 348 349LOAD_NODE_MODULES(X, START) 3501. let DIRS = NODE_MODULES_PATHS(START) 3512. for each DIR in DIRS: 352 a. LOAD_PACKAGE_EXPORTS(X, DIR) 353 b. LOAD_AS_FILE(DIR/X) 354 c. LOAD_AS_DIRECTORY(DIR/X) 355 356NODE_MODULES_PATHS(START) 3571. let PARTS = path split(START) 3582. let I = count of PARTS - 1 3593. let DIRS = [GLOBAL_FOLDERS] 3604. while I >= 0, 361 a. if PARTS[I] = "node_modules" CONTINUE 362 b. DIR = path join(PARTS[0 .. I] + "node_modules") 363 c. DIRS = DIRS + DIR 364 d. let I = I - 1 3655. return DIRS 366 367LOAD_PACKAGE_IMPORTS(X, DIR) 3681. Find the closest package scope SCOPE to DIR. 3692. If no scope was found, return. 3703. If the SCOPE/package.json "imports" is null or undefined, return. 3714. let MATCH = PACKAGE_IMPORTS_RESOLVE(X, pathToFileURL(SCOPE), 372 ["node", "require"]) <a href="esm.md#resolver-algorithm-specification">defined in the ESM resolver</a>. 3735. RESOLVE_ESM_MATCH(MATCH). 374 375LOAD_PACKAGE_EXPORTS(X, DIR) 3761. Try to interpret X as a combination of NAME and SUBPATH where the name 377 may have a @scope/ prefix and the subpath begins with a slash (`/`). 3782. If X does not match this pattern or DIR/NAME/package.json is not a file, 379 return. 3803. Parse DIR/NAME/package.json, and look for "exports" field. 3814. If "exports" is null or undefined, return. 3825. let MATCH = PACKAGE_EXPORTS_RESOLVE(pathToFileURL(DIR/NAME), "." + SUBPATH, 383 `package.json` "exports", ["node", "require"]) <a href="esm.md#resolver-algorithm-specification">defined in the ESM resolver</a>. 3846. RESOLVE_ESM_MATCH(MATCH) 385 386LOAD_PACKAGE_SELF(X, DIR) 3871. Find the closest package scope SCOPE to DIR. 3882. If no scope was found, return. 3893. If the SCOPE/package.json "exports" is null or undefined, return. 3904. If the SCOPE/package.json "name" is not the first segment of X, return. 3915. let MATCH = PACKAGE_EXPORTS_RESOLVE(pathToFileURL(SCOPE), 392 "." + X.slice("name".length), `package.json` "exports", ["node", "require"]) 393 <a href="esm.md#resolver-algorithm-specification">defined in the ESM resolver</a>. 3946. RESOLVE_ESM_MATCH(MATCH) 395 396RESOLVE_ESM_MATCH(MATCH) 3971. let { RESOLVED, EXACT } = MATCH 3982. let RESOLVED_PATH = fileURLToPath(RESOLVED) 3993. If EXACT is true, 400 a. If the file at RESOLVED_PATH exists, load RESOLVED_PATH as its extension 401 format. STOP 4024. Otherwise, if EXACT is false, 403 a. LOAD_AS_FILE(RESOLVED_PATH) 404 b. LOAD_AS_DIRECTORY(RESOLVED_PATH) 4055. THROW "not found" 406</pre> 407</section><section><h3>Caching<span><a class="mark" href="#modules_caching" id="modules_caching">#</a></span></h3> 408 409<p>Modules are cached after the first time they are loaded. This means (among other 410things) that every call to <code>require('foo')</code> will get exactly the same object 411returned, if it would resolve to the same file.</p> 412<p>Provided <code>require.cache</code> is not modified, multiple calls to <code>require('foo')</code> 413will not cause the module code to be executed multiple times. This is an 414important feature. With it, "partially done" objects can be returned, thus 415allowing transitive dependencies to be loaded even when they would cause cycles.</p> 416<p>To have a module execute code multiple times, export a function, and call that 417function.</p> 418<h4>Module caching caveats<span><a class="mark" href="#modules_module_caching_caveats" id="modules_module_caching_caveats">#</a></span></h4> 419 420<p>Modules are cached based on their resolved filename. Since modules may resolve 421to a different filename based on the location of the calling module (loading 422from <code>node_modules</code> folders), it is not a <em>guarantee</em> that <code>require('foo')</code> will 423always return the exact same object, if it would resolve to different files.</p> 424<p>Additionally, on case-insensitive file systems or operating systems, different 425resolved filenames can point to the same file, but the cache will still treat 426them as different modules and will reload the file multiple times. For example, 427<code>require('./foo')</code> and <code>require('./FOO')</code> return two different objects, 428irrespective of whether or not <code>./foo</code> and <code>./FOO</code> are the same file.</p> 429</section><section><h3>Core modules<span><a class="mark" href="#modules_core_modules" id="modules_core_modules">#</a></span></h3> 430 431<div class="api_metadata"> 432<details class="changelog"><summary>History</summary> 433<table> 434<tbody><tr><th>Version</th><th>Changes</th></tr> 435<tr><td>v14.18.0</td> 436<td><p>Added <code>node:</code> import support to <code>require(...)</code>.</p></td></tr> 437</tbody></table> 438</details> 439</div> 440<p>Node.js has several modules compiled into the binary. These modules are 441described in greater detail elsewhere in this documentation.</p> 442<p>The core modules are defined within the Node.js source and are located in the 443<code>lib/</code> folder.</p> 444<p>Core modules are always preferentially loaded if their identifier is 445passed to <code>require()</code>. For instance, <code>require('http')</code> will always 446return the built in HTTP module, even if there is a file by that name.</p> 447<p>Core modules can also be identified using the <code>node:</code> prefix, in which case 448it bypasses the <code>require</code> cache. For instance, <code>require('node:http')</code> will 449always return the built in HTTP module, even if there is <code>require.cache</code> entry 450by that name.</p> 451</section><section><h3>Cycles<span><a class="mark" href="#modules_cycles" id="modules_cycles">#</a></span></h3> 452 453<p>When there are circular <code>require()</code> calls, a module might not have finished 454executing when it is returned.</p> 455<p>Consider this situation:</p> 456<p><code>a.js</code>:</p> 457<pre><code class="language-js"><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'a starting'</span>); 458<span class="hljs-built_in">exports</span>.<span class="hljs-property">done</span> = <span class="hljs-literal">false</span>; 459<span class="hljs-keyword">const</span> b = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./b.js'</span>); 460<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'in a, b.done = %j'</span>, b.<span class="hljs-property">done</span>); 461<span class="hljs-built_in">exports</span>.<span class="hljs-property">done</span> = <span class="hljs-literal">true</span>; 462<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'a done'</span>);</code></pre> 463<p><code>b.js</code>:</p> 464<pre><code class="language-js"><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'b starting'</span>); 465<span class="hljs-built_in">exports</span>.<span class="hljs-property">done</span> = <span class="hljs-literal">false</span>; 466<span class="hljs-keyword">const</span> a = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./a.js'</span>); 467<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'in b, a.done = %j'</span>, a.<span class="hljs-property">done</span>); 468<span class="hljs-built_in">exports</span>.<span class="hljs-property">done</span> = <span class="hljs-literal">true</span>; 469<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'b done'</span>);</code></pre> 470<p><code>main.js</code>:</p> 471<pre><code class="language-js"><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'main starting'</span>); 472<span class="hljs-keyword">const</span> a = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./a.js'</span>); 473<span class="hljs-keyword">const</span> b = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./b.js'</span>); 474<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'in main, a.done = %j, b.done = %j'</span>, a.<span class="hljs-property">done</span>, b.<span class="hljs-property">done</span>);</code></pre> 475<p>When <code>main.js</code> loads <code>a.js</code>, then <code>a.js</code> in turn loads <code>b.js</code>. At that 476point, <code>b.js</code> tries to load <code>a.js</code>. In order to prevent an infinite 477loop, an <strong>unfinished copy</strong> of the <code>a.js</code> exports object is returned to the 478<code>b.js</code> module. <code>b.js</code> then finishes loading, and its <code>exports</code> object is 479provided to the <code>a.js</code> module.</p> 480<p>By the time <code>main.js</code> has loaded both modules, they're both finished. 481The output of this program would thus be:</p> 482<pre><code class="language-console"><span class="hljs-meta">$ </span><span class="language-bash">node main.js</span> 483main starting 484a starting 485b starting 486in b, a.done = false 487b done 488in a, b.done = true 489a done 490in main, a.done = true, b.done = true</code></pre> 491<p>Careful planning is required to allow cyclic module dependencies to work 492correctly within an application.</p> 493</section><section><h3>File modules<span><a class="mark" href="#modules_file_modules" id="modules_file_modules">#</a></span></h3> 494 495<p>If the exact filename is not found, then Node.js will attempt to load the 496required filename with the added extensions: <code>.js</code>, <code>.json</code>, and finally 497<code>.node</code>.</p> 498<p><code>.js</code> files are interpreted as JavaScript text files, and <code>.json</code> files are 499parsed as JSON text files. <code>.node</code> files are interpreted as compiled addon 500modules loaded with <code>process.dlopen()</code>.</p> 501<p>A required module prefixed with <code>'/'</code> is an absolute path to the file. For 502example, <code>require('/home/marco/foo.js')</code> will load the file at 503<code>/home/marco/foo.js</code>.</p> 504<p>A required module prefixed with <code>'./'</code> is relative to the file calling 505<code>require()</code>. That is, <code>circle.js</code> must be in the same directory as <code>foo.js</code> for 506<code>require('./circle')</code> to find it.</p> 507<p>Without a leading <code>'/'</code>, <code>'./'</code>, or <code>'../'</code> to indicate a file, the module must 508either be a core module or is loaded from a <code>node_modules</code> folder.</p> 509<p>If the given path does not exist, <code>require()</code> will throw an <a href="errors.html#errors_class_error"><code>Error</code></a> with its 510<code>code</code> property set to <code>'MODULE_NOT_FOUND'</code>.</p> 511</section><section><h3>Folders as modules<span><a class="mark" href="#modules_folders_as_modules" id="modules_folders_as_modules">#</a></span></h3> 512 513<p>It is convenient to organize programs and libraries into self-contained 514directories, and then provide a single entry point to those directories. 515There are three ways in which a folder may be passed to <code>require()</code> as 516an argument.</p> 517<p>The first is to create a <a href="packages.html#packages_node_js_package_json_field_definitions"><code>package.json</code></a> file in the root of the folder, 518which specifies a <code>main</code> module. An example <a href="packages.html#packages_node_js_package_json_field_definitions"><code>package.json</code></a> file might 519look like this:</p> 520<pre><code class="language-json"><span class="hljs-punctuation">{</span> <span class="hljs-attr">"name"</span> <span class="hljs-punctuation">:</span> <span class="hljs-string">"some-library"</span><span class="hljs-punctuation">,</span> 521 <span class="hljs-attr">"main"</span> <span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/some-library.js"</span> <span class="hljs-punctuation">}</span></code></pre> 522<p>If this was in a folder at <code>./some-library</code>, then 523<code>require('./some-library')</code> would attempt to load 524<code>./some-library/lib/some-library.js</code>.</p> 525<p>This is the extent of the awareness of <code>package.json</code> files within Node.js.</p> 526<p>If there is no <a href="packages.html#packages_node_js_package_json_field_definitions"><code>package.json</code></a> file present in the directory, or if the 527<a href="packages.html#packages_main"><code>"main"</code></a> entry is missing or cannot be resolved, then Node.js 528will attempt to load an <code>index.js</code> or <code>index.node</code> file out of that 529directory. For example, if there was no <a href="packages.html#packages_node_js_package_json_field_definitions"><code>package.json</code></a> file in the previous 530example, then <code>require('./some-library')</code> would attempt to load:</p> 531<ul> 532<li><code>./some-library/index.js</code></li> 533<li><code>./some-library/index.node</code></li> 534</ul> 535<p>If these attempts fail, then Node.js will report the entire module as missing 536with the default error:</p> 537<pre><code class="language-console">Error: Cannot find module 'some-library'</code></pre> 538</section><section><h3>Loading from <code>node_modules</code> folders<span><a class="mark" href="#modules_loading_from_node_modules_folders" id="modules_loading_from_node_modules_folders">#</a></span></h3> 539 540<p>If the module identifier passed to <code>require()</code> is not a 541<a href="#modules_core_modules">core</a> module, and does not begin with <code>'/'</code>, <code>'../'</code>, or 542<code>'./'</code>, then Node.js starts at the parent directory of the current module, and 543adds <code>/node_modules</code>, and attempts to load the module from that location. 544Node.js will not append <code>node_modules</code> to a path already ending in 545<code>node_modules</code>.</p> 546<p>If it is not found there, then it moves to the parent directory, and so 547on, until the root of the file system is reached.</p> 548<p>For example, if the file at <code>'/home/ry/projects/foo.js'</code> called 549<code>require('bar.js')</code>, then Node.js would look in the following locations, in 550this order:</p> 551<ul> 552<li><code>/home/ry/projects/node_modules/bar.js</code></li> 553<li><code>/home/ry/node_modules/bar.js</code></li> 554<li><code>/home/node_modules/bar.js</code></li> 555<li><code>/node_modules/bar.js</code></li> 556</ul> 557<p>This allows programs to localize their dependencies, so that they do not 558clash.</p> 559<p>It is possible to require specific files or sub modules distributed with a 560module by including a path suffix after the module name. For instance 561<code>require('example-module/path/to/file')</code> would resolve <code>path/to/file</code> 562relative to where <code>example-module</code> is located. The suffixed path follows the 563same module resolution semantics.</p> 564</section><section><h3>Loading from the global folders<span><a class="mark" href="#modules_loading_from_the_global_folders" id="modules_loading_from_the_global_folders">#</a></span></h3> 565 566<p>If the <code>NODE_PATH</code> environment variable is set to a colon-delimited list 567of absolute paths, then Node.js will search those paths for modules if they 568are not found elsewhere.</p> 569<p>On Windows, <code>NODE_PATH</code> is delimited by semicolons (<code>;</code>) instead of colons.</p> 570<p><code>NODE_PATH</code> was originally created to support loading modules from 571varying paths before the current <a href="#modules_all_together">module resolution</a> algorithm was defined.</p> 572<p><code>NODE_PATH</code> is still supported, but is less necessary now that the Node.js 573ecosystem has settled on a convention for locating dependent modules. 574Sometimes deployments that rely on <code>NODE_PATH</code> show surprising behavior 575when people are unaware that <code>NODE_PATH</code> must be set. Sometimes a 576module's dependencies change, causing a different version (or even a 577different module) to be loaded as the <code>NODE_PATH</code> is searched.</p> 578<p>Additionally, Node.js will search in the following list of GLOBAL_FOLDERS:</p> 579<ul> 580<li>1: <code>$HOME/.node_modules</code></li> 581<li>2: <code>$HOME/.node_libraries</code></li> 582<li>3: <code>$PREFIX/lib/node</code></li> 583</ul> 584<p>Where <code>$HOME</code> is the user's home directory, and <code>$PREFIX</code> is the Node.js 585configured <code>node_prefix</code>.</p> 586<p>These are mostly for historic reasons.</p> 587<p>It is strongly encouraged to place dependencies in the local <code>node_modules</code> 588folder. These will be loaded faster, and more reliably.</p> 589</section><section><h3>The module wrapper<span><a class="mark" href="#modules_the_module_wrapper" id="modules_the_module_wrapper">#</a></span></h3> 590 591<p>Before a module's code is executed, Node.js will wrap it with a function 592wrapper that looks like the following:</p> 593<pre><code class="language-js">(<span class="hljs-keyword">function</span>(<span class="hljs-params"><span class="hljs-built_in">exports</span>, <span class="hljs-built_in">require</span>, <span class="hljs-variable language_">module</span>, __filename, __dirname</span>) { 594<span class="hljs-comment">// Module code actually lives in here</span> 595});</code></pre> 596<p>By doing this, Node.js achieves a few things:</p> 597<ul> 598<li>It keeps top-level variables (defined with <code>var</code>, <code>const</code> or <code>let</code>) scoped to 599the module rather than the global object.</li> 600<li>It helps to provide some global-looking variables that are actually specific 601to the module, such as: 602<ul> 603<li>The <code>module</code> and <code>exports</code> objects that the implementor can use to export 604values from the module.</li> 605<li>The convenience variables <code>__filename</code> and <code>__dirname</code>, containing the 606module's absolute filename and directory path.</li> 607</ul> 608</li> 609</ul> 610</section><section><h3>The module scope<span><a class="mark" href="#modules_the_module_scope" id="modules_the_module_scope">#</a></span></h3> 611<h4><code>__dirname</code><span><a class="mark" href="#modules_dirname" id="modules_dirname">#</a></span></h4> 612<div class="api_metadata"> 613<span>Added in: v0.1.27</span> 614</div> 615 616<ul> 617<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 618</ul> 619<p>The directory name of the current module. This is the same as the 620<a href="path.html#path_path_dirname_path"><code>path.dirname()</code></a> of the <a href="#modules_filename"><code>__filename</code></a>.</p> 621<p>Example: running <code>node example.js</code> from <code>/Users/mjr</code></p> 622<pre><code class="language-js"><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(__dirname); 623<span class="hljs-comment">// Prints: /Users/mjr</span> 624<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(path.<span class="hljs-title function_">dirname</span>(__filename)); 625<span class="hljs-comment">// Prints: /Users/mjr</span></code></pre> 626<h4><code>__filename</code><span><a class="mark" href="#modules_filename" id="modules_filename">#</a></span></h4> 627<div class="api_metadata"> 628<span>Added in: v0.0.1</span> 629</div> 630 631<ul> 632<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 633</ul> 634<p>The file name of the current module. This is the current module file's absolute 635path with symlinks resolved.</p> 636<p>For a main program this is not necessarily the same as the file name used in the 637command line.</p> 638<p>See <a href="#modules_dirname"><code>__dirname</code></a> for the directory name of the current module.</p> 639<p>Examples:</p> 640<p>Running <code>node example.js</code> from <code>/Users/mjr</code></p> 641<pre><code class="language-js"><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(__filename); 642<span class="hljs-comment">// Prints: /Users/mjr/example.js</span> 643<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(__dirname); 644<span class="hljs-comment">// Prints: /Users/mjr</span></code></pre> 645<p>Given two modules: <code>a</code> and <code>b</code>, where <code>b</code> is a dependency of 646<code>a</code> and there is a directory structure of:</p> 647<ul> 648<li><code>/Users/mjr/app/a.js</code></li> 649<li><code>/Users/mjr/app/node_modules/b/b.js</code></li> 650</ul> 651<p>References to <code>__filename</code> within <code>b.js</code> will return 652<code>/Users/mjr/app/node_modules/b/b.js</code> while references to <code>__filename</code> within 653<code>a.js</code> will return <code>/Users/mjr/app/a.js</code>.</p> 654<h4><code>exports</code><span><a class="mark" href="#modules_exports" id="modules_exports">#</a></span></h4> 655<div class="api_metadata"> 656<span>Added in: v0.1.12</span> 657</div> 658 659<ul> 660<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 661</ul> 662<p>A reference to the <code>module.exports</code> that is shorter to type. 663See the section about the <a href="#modules_exports_shortcut">exports shortcut</a> for details on when to use 664<code>exports</code> and when to use <code>module.exports</code>.</p> 665<h4><code>module</code><span><a class="mark" href="#modules_module" id="modules_module">#</a></span></h4> 666<div class="api_metadata"> 667<span>Added in: v0.1.16</span> 668</div> 669 670<ul> 671<li><a href="modules.html#modules_the_module_object" class="type"><module></a></li> 672</ul> 673<p>A reference to the current module, see the section about the 674<a href="#modules_the_module_object"><code>module</code> object</a>. In particular, <code>module.exports</code> is used for defining what 675a module exports and makes available through <code>require()</code>.</p> 676<h4><code>require(id)</code><span><a class="mark" href="#modules_require_id" id="modules_require_id">#</a></span></h4> 677<div class="api_metadata"> 678<span>Added in: v0.1.13</span> 679</div> 680 681<ul> 682<li><code>id</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> module name or path</li> 683<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> exported module content</li> 684</ul> 685<p>Used to import modules, <code>JSON</code>, and local files. Modules can be imported 686from <code>node_modules</code>. Local modules and JSON files can be imported using 687a relative path (e.g. <code>./</code>, <code>./foo</code>, <code>./bar/baz</code>, <code>../foo</code>) that will be 688resolved against the directory named by <a href="#modules_dirname"><code>__dirname</code></a> (if defined) or 689the current working directory. The relative paths of POSIX style are resolved 690in an OS independent fashion, meaning that the examples above will work on 691Windows in the same way they would on Unix systems.</p> 692<pre><code class="language-js"><span class="hljs-comment">// Importing a local module with a path relative to the `__dirname` or current</span> 693<span class="hljs-comment">// working directory. (On Windows, this would resolve to .\path\myLocalModule.)</span> 694<span class="hljs-keyword">const</span> myLocalModule = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./path/myLocalModule'</span>); 695 696<span class="hljs-comment">// Importing a JSON file:</span> 697<span class="hljs-keyword">const</span> jsonData = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./path/filename.json'</span>); 698 699<span class="hljs-comment">// Importing a module from node_modules or Node.js built-in module:</span> 700<span class="hljs-keyword">const</span> crypto = <span class="hljs-built_in">require</span>(<span class="hljs-string">'crypto'</span>);</code></pre> 701<h5><code>require.cache</code><span><a class="mark" href="#modules_require_cache" id="modules_require_cache">#</a></span></h5> 702<div class="api_metadata"> 703<span>Added in: v0.3.0</span> 704</div> 705<ul> 706<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 707</ul> 708<p>Modules are cached in this object when they are required. By deleting a key 709value from this object, the next <code>require</code> will reload the module. 710This does not apply to <a href="addons.html">native addons</a>, for which reloading will result in an 711error.</p> 712<p>Adding or replacing entries is also possible. This cache is checked before 713native modules and if a name matching a native module is added to the cache, 714only <code>node:</code>-prefixed require calls are going to receive the native module. 715Use with care!</p> 716<!-- eslint-disable node-core/no-duplicate-requires --> 717<pre><code class="language-js"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'assert'</span>); 718<span class="hljs-keyword">const</span> realFs = <span class="hljs-built_in">require</span>(<span class="hljs-string">'fs'</span>); 719 720<span class="hljs-keyword">const</span> fakeFs = {}; 721<span class="hljs-built_in">require</span>.<span class="hljs-property">cache</span>.<span class="hljs-property">fs</span> = { <span class="hljs-attr">exports</span>: fakeFs }; 722 723assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-built_in">require</span>(<span class="hljs-string">'fs'</span>), fakeFs); 724assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-built_in">require</span>(<span class="hljs-string">'node:fs'</span>), realFs);</code></pre> 725<h5><code>require.extensions</code><span><a class="mark" href="#modules_require_extensions" id="modules_require_extensions">#</a></span></h5> 726<div class="api_metadata"> 727<span>Added in: v0.3.0</span><span>Deprecated since: v0.10.6</span> 728</div> 729<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated</div><p></p> 730<ul> 731<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 732</ul> 733<p>Instruct <code>require</code> on how to handle certain file extensions.</p> 734<p>Process files with the extension <code>.sjs</code> as <code>.js</code>:</p> 735<pre><code class="language-js"><span class="hljs-built_in">require</span>.<span class="hljs-property">extensions</span>[<span class="hljs-string">'.sjs'</span>] = <span class="hljs-built_in">require</span>.<span class="hljs-property">extensions</span>[<span class="hljs-string">'.js'</span>];</code></pre> 736<p><strong>Deprecated.</strong> In the past, this list has been used to load non-JavaScript 737modules into Node.js by compiling them on-demand. However, in practice, there 738are much better ways to do this, such as loading modules via some other Node.js 739program, or compiling them to JavaScript ahead of time.</p> 740<p>Avoid using <code>require.extensions</code>. Use could cause subtle bugs and resolving the 741extensions gets slower with each registered extension.</p> 742<h5><code>require.main</code><span><a class="mark" href="#modules_require_main" id="modules_require_main">#</a></span></h5> 743<div class="api_metadata"> 744<span>Added in: v0.1.17</span> 745</div> 746<ul> 747<li><a href="modules.html#modules_the_module_object" class="type"><module></a></li> 748</ul> 749<p>The <code>Module</code> object representing the entry script loaded when the Node.js 750process launched. 751See <a href="#modules_accessing_the_main_module">"Accessing the main module"</a>.</p> 752<p>In <code>entry.js</code> script:</p> 753<pre><code class="language-js"><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-built_in">require</span>.<span class="hljs-property">main</span>);</code></pre> 754<pre><code class="language-bash">node entry.js</code></pre> 755<!-- eslint-skip --> 756<pre><code class="language-js"><span class="hljs-title class_">Module</span> { 757 <span class="hljs-attr">id</span>: <span class="hljs-string">'.'</span>, 758 <span class="hljs-attr">path</span>: <span class="hljs-string">'/absolute/path/to'</span>, 759 <span class="hljs-attr">exports</span>: {}, 760 <span class="hljs-attr">parent</span>: <span class="hljs-literal">null</span>, 761 <span class="hljs-attr">filename</span>: <span class="hljs-string">'/absolute/path/to/entry.js'</span>, 762 <span class="hljs-attr">loaded</span>: <span class="hljs-literal">false</span>, 763 <span class="hljs-attr">children</span>: [], 764 <span class="hljs-attr">paths</span>: 765 [ <span class="hljs-string">'/absolute/path/to/node_modules'</span>, 766 <span class="hljs-string">'/absolute/path/node_modules'</span>, 767 <span class="hljs-string">'/absolute/node_modules'</span>, 768 <span class="hljs-string">'/node_modules'</span> ] }</code></pre> 769<h5><code>require.resolve(request[, options])</code><span><a class="mark" href="#modules_require_resolve_request_options" id="modules_require_resolve_request_options">#</a></span></h5> 770<div class="api_metadata"> 771<details class="changelog"><summary>History</summary> 772<table> 773<tbody><tr><th>Version</th><th>Changes</th></tr> 774<tr><td>v8.9.0</td> 775<td><p>The <code>paths</code> option is now supported.</p></td></tr> 776<tr><td>v0.3.0</td> 777<td><p><span>Added in: v0.3.0</span></p></td></tr> 778</tbody></table> 779</details> 780</div> 781<ul> 782<li><code>request</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The module path to resolve.</li> 783<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 784<ul> 785<li><code>paths</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> Paths to resolve module location from. If present, these 786paths are used instead of the default resolution paths, with the exception 787of <a href="#modules_loading_from_the_global_folders">GLOBAL_FOLDERS</a> like <code>$HOME/.node_modules</code>, which are always 788included. Each of these paths is used as a starting point for 789the module resolution algorithm, meaning that the <code>node_modules</code> hierarchy 790is checked from this location.</li> 791</ul> 792</li> 793<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 794</ul> 795<p>Use the internal <code>require()</code> machinery to look up the location of a module, 796but rather than loading the module, just return the resolved filename.</p> 797<p>If the module can not be found, a <code>MODULE_NOT_FOUND</code> error is thrown.</p> 798<h6><code>require.resolve.paths(request)</code><span><a class="mark" href="#modules_require_resolve_paths_request" id="modules_require_resolve_paths_request">#</a></span></h6> 799<div class="api_metadata"> 800<span>Added in: v8.9.0</span> 801</div> 802<ul> 803<li><code>request</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The module path whose lookup paths are being retrieved.</li> 804<li>Returns: <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/Web/JavaScript/Data_structures#Null_type" class="type"><null></a></li> 805</ul> 806<p>Returns an array containing the paths searched during resolution of <code>request</code> or 807<code>null</code> if the <code>request</code> string references a core module, for example <code>http</code> or 808<code>fs</code>.</p> 809</section><section><h3>The <code>module</code> object<span><a class="mark" href="#modules_the_module_object" id="modules_the_module_object">#</a></span></h3> 810<div class="api_metadata"> 811<span>Added in: v0.1.16</span> 812</div> 813 814 815<ul> 816<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 817</ul> 818<p>In each module, the <code>module</code> free variable is a reference to the object 819representing the current module. For convenience, <code>module.exports</code> is 820also accessible via the <code>exports</code> module-global. <code>module</code> is not actually 821a global but rather local to each module.</p> 822<h4><code>module.children</code><span><a class="mark" href="#modules_module_children" id="modules_module_children">#</a></span></h4> 823<div class="api_metadata"> 824<span>Added in: v0.1.16</span> 825</div> 826<ul> 827<li><a href="modules.html#modules_the_module_object" class="type"><module[]></a></li> 828</ul> 829<p>The module objects required for the first time by this one.</p> 830<h4><code>module.exports</code><span><a class="mark" href="#modules_module_exports" id="modules_module_exports">#</a></span></h4> 831<div class="api_metadata"> 832<span>Added in: v0.1.16</span> 833</div> 834<ul> 835<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 836</ul> 837<p>The <code>module.exports</code> object is created by the <code>Module</code> system. Sometimes this is 838not acceptable; many want their module to be an instance of some class. To do 839this, assign the desired export object to <code>module.exports</code>. Assigning 840the desired object to <code>exports</code> will simply rebind the local <code>exports</code> variable, 841which is probably not what is desired.</p> 842<p>For example, suppose we were making a module called <code>a.js</code>:</p> 843<pre><code class="language-js"><span class="hljs-keyword">const</span> <span class="hljs-title class_">EventEmitter</span> = <span class="hljs-built_in">require</span>(<span class="hljs-string">'events'</span>); 844 845<span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span> = <span class="hljs-keyword">new</span> <span class="hljs-title class_">EventEmitter</span>(); 846 847<span class="hljs-comment">// Do some work, and after some time emit</span> 848<span class="hljs-comment">// the 'ready' event from the module itself.</span> 849<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 850 <span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span>.<span class="hljs-title function_">emit</span>(<span class="hljs-string">'ready'</span>); 851}, <span class="hljs-number">1000</span>);</code></pre> 852<p>Then in another file we could do:</p> 853<pre><code class="language-js"><span class="hljs-keyword">const</span> a = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./a'</span>); 854a.<span class="hljs-title function_">on</span>(<span class="hljs-string">'ready'</span>, <span class="hljs-function">() =></span> { 855 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'module "a" is ready'</span>); 856});</code></pre> 857<p>Assignment to <code>module.exports</code> must be done immediately. It cannot be 858done in any callbacks. This does not work:</p> 859<p><code>x.js</code>:</p> 860<pre><code class="language-js"><span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> { 861 <span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span> = { <span class="hljs-attr">a</span>: <span class="hljs-string">'hello'</span> }; 862}, <span class="hljs-number">0</span>);</code></pre> 863<p><code>y.js</code>:</p> 864<pre><code class="language-js"><span class="hljs-keyword">const</span> x = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./x'</span>); 865<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(x.<span class="hljs-property">a</span>);</code></pre> 866<h5><code>exports</code> shortcut<span><a class="mark" href="#modules_exports_shortcut" id="modules_exports_shortcut">#</a></span></h5> 867<div class="api_metadata"> 868<span>Added in: v0.1.16</span> 869</div> 870<p>The <code>exports</code> variable is available within a module's file-level scope, and is 871assigned the value of <code>module.exports</code> before the module is evaluated.</p> 872<p>It allows a shortcut, so that <code>module.exports.f = ...</code> can be written more 873succinctly as <code>exports.f = ...</code>. However, be aware that like any variable, if a 874new value is assigned to <code>exports</code>, it is no longer bound to <code>module.exports</code>:</p> 875<pre><code class="language-js"><span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span>.<span class="hljs-property">hello</span> = <span class="hljs-literal">true</span>; <span class="hljs-comment">// Exported from require of module</span> 876<span class="hljs-built_in">exports</span> = { <span class="hljs-attr">hello</span>: <span class="hljs-literal">false</span> }; <span class="hljs-comment">// Not exported, only available in the module</span></code></pre> 877<p>When the <code>module.exports</code> property is being completely replaced by a new 878object, it is common to also reassign <code>exports</code>:</p> 879<!-- eslint-disable func-name-matching --> 880<pre><code class="language-js"><span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span> = <span class="hljs-built_in">exports</span> = <span class="hljs-keyword">function</span> <span class="hljs-title function_">Constructor</span>(<span class="hljs-params"></span>) { 881 <span class="hljs-comment">// ... etc.</span> 882};</code></pre> 883<p>To illustrate the behavior, imagine this hypothetical implementation of 884<code>require()</code>, which is quite similar to what is actually done by <code>require()</code>:</p> 885<pre><code class="language-js"><span class="hljs-keyword">function</span> <span class="hljs-title function_">require</span>(<span class="hljs-params"><span class="hljs-comment">/* ... */</span></span>) { 886 <span class="hljs-keyword">const</span> <span class="hljs-variable language_">module</span> = { <span class="hljs-attr">exports</span>: {} }; 887 (<span class="hljs-function">(<span class="hljs-params"><span class="hljs-variable language_">module</span>, <span class="hljs-built_in">exports</span></span>) =></span> { 888 <span class="hljs-comment">// Module code here. In this example, define a function.</span> 889 <span class="hljs-keyword">function</span> <span class="hljs-title function_">someFunc</span>(<span class="hljs-params"></span>) {} 890 <span class="hljs-built_in">exports</span> = someFunc; 891 <span class="hljs-comment">// At this point, exports is no longer a shortcut to module.exports, and</span> 892 <span class="hljs-comment">// this module will still export an empty default object.</span> 893 <span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span> = someFunc; 894 <span class="hljs-comment">// At this point, the module will now export someFunc, instead of the</span> 895 <span class="hljs-comment">// default object.</span> 896 })(<span class="hljs-variable language_">module</span>, <span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span>); 897 <span class="hljs-keyword">return</span> <span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span>; 898}</code></pre> 899<h4><code>module.filename</code><span><a class="mark" href="#modules_module_filename" id="modules_module_filename">#</a></span></h4> 900<div class="api_metadata"> 901<span>Added in: v0.1.16</span> 902</div> 903<ul> 904<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 905</ul> 906<p>The fully resolved filename of the module.</p> 907<h4><code>module.id</code><span><a class="mark" href="#modules_module_id" id="modules_module_id">#</a></span></h4> 908<div class="api_metadata"> 909<span>Added in: v0.1.16</span> 910</div> 911<ul> 912<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 913</ul> 914<p>The identifier for the module. Typically this is the fully resolved 915filename.</p> 916<h4><code>module.isPreloading</code><span><a class="mark" href="#modules_module_ispreloading" id="modules_module_ispreloading">#</a></span></h4> 917<div class="api_metadata"> 918<span>Added in: v14.17.0</span> 919</div> 920<ul> 921<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if the module is running during the Node.js preload 922phase.</li> 923</ul> 924<h4><code>module.loaded</code><span><a class="mark" href="#modules_module_loaded" id="modules_module_loaded">#</a></span></h4> 925<div class="api_metadata"> 926<span>Added in: v0.1.16</span> 927</div> 928<ul> 929<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 930</ul> 931<p>Whether or not the module is done loading, or is in the process of 932loading.</p> 933<h4><code>module.parent</code><span><a class="mark" href="#modules_module_parent" id="modules_module_parent">#</a></span></h4> 934<div class="api_metadata"> 935<span>Added in: v0.1.16</span><span>Deprecated since: v14.6.0, v12.19.0</span> 936</div> 937<p></p><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Please use <a href="#modules_require_main"><code>require.main</code></a> and 938<a href="#modules_module_children"><code>module.children</code></a> instead.</div><p></p> 939<ul> 940<li><a href="modules.html#modules_the_module_object" class="type"><module></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Null_type" class="type"><null></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Undefined_type" class="type"><undefined></a></li> 941</ul> 942<p>The module that first required this one, or <code>null</code> if the current module is the 943entry point of the current process, or <code>undefined</code> if the module was loaded by 944something that is not a CommonJS module (E.G.: REPL or <code>import</code>).</p> 945<h4><code>module.path</code><span><a class="mark" href="#modules_module_path" id="modules_module_path">#</a></span></h4> 946<div class="api_metadata"> 947<span>Added in: v11.14.0</span> 948</div> 949<ul> 950<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 951</ul> 952<p>The directory name of the module. This is usually the same as the 953<a href="path.html#path_path_dirname_path"><code>path.dirname()</code></a> of the <a href="#modules_module_id"><code>module.id</code></a>.</p> 954<h4><code>module.paths</code><span><a class="mark" href="#modules_module_paths" id="modules_module_paths">#</a></span></h4> 955<div class="api_metadata"> 956<span>Added in: v0.4.0</span> 957</div> 958<ul> 959<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 960</ul> 961<p>The search paths for the module.</p> 962<h4><code>module.require(id)</code><span><a class="mark" href="#modules_module_require_id" id="modules_module_require_id">#</a></span></h4> 963<div class="api_metadata"> 964<span>Added in: v0.5.1</span> 965</div> 966<ul> 967<li><code>id</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 968<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> exported module content</li> 969</ul> 970<p>The <code>module.require()</code> method provides a way to load a module as if 971<code>require()</code> was called from the original module.</p> 972<p>In order to do this, it is necessary to get a reference to the <code>module</code> object. 973Since <code>require()</code> returns the <code>module.exports</code>, and the <code>module</code> is typically 974<em>only</em> available within a specific module's code, it must be explicitly exported 975in order to be used.</p> 976</section><section><h3>The <code>Module</code> object<span><a class="mark" href="#modules_the_module_object_1" id="modules_the_module_object_1">#</a></span></h3> 977<p>This section was moved to 978<a href="module.html#module_the_module_object">Modules: <code>module</code> core module</a>.</p> 979<!-- Anchors to make sure old links find a target --> 980<ul> 981<li><a id="modules_module_builtinmodules" href="module.html#module_module_builtinmodules"><code>module.builtinModules</code></a></li> 982<li><a id="modules_module_createrequire_filename" href="module.html#module_module_createrequire_filename"><code>module.createRequire(filename)</code></a></li> 983<li><a id="modules_module_createrequirefrompath_filename" href="module.html#module_module_createrequirefrompath_filename"><code>module.createRequireFromPath(filename)</code></a></li> 984<li><a id="modules_module_syncbuiltinesmexports" href="module.html#module_module_syncbuiltinesmexports"><code>module.syncBuiltinESMExports()</code></a></li> 985</ul> 986</section><section><h3>Source map v3 support<span><a class="mark" href="#modules_source_map_v3_support" id="modules_source_map_v3_support">#</a></span></h3> 987<p>This section was moved to 988<a href="module.html#module_source_map_v3_support">Modules: <code>module</code> core module</a>.</p> 989<!-- Anchors to make sure old links find a target --> 990<ul> 991<li><a id="modules_module_findsourcemap_path_error" href="module.html#module_module_findsourcemap_path"><code>module.findSourceMap(path)</code></a></li> 992<li><a id="modules_class_module_sourcemap" href="module.html#module_class_module_sourcemap">Class: <code>module.SourceMap</code></a> 993<ul> 994<li><a id="modules_new_sourcemap_payload" href="module.html#module_new_sourcemap_payload"><code>new SourceMap(payload)</code></a></li> 995<li><a id="modules_sourcemap_payload" href="module.html#module_sourcemap_payload"><code>sourceMap.payload</code></a></li> 996<li><a id="modules_sourcemap_findentry_linenumber_columnnumber" href="module.html#module_sourcemap_findentry_linenumber_columnnumber"><code>sourceMap.findEntry(lineNumber, columnNumber)</code></a></li> 997</ul> 998</li> 999</ul></section> 1000 <!-- API END --> 1001 </div> 1002 </div> 1003 </div> 1004 <script> 1005 'use strict'; 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