Modules: CommonJS modules | Node.js v22.8.0 Documentation (2024)

Enabling#

Node.js has two module systems: CommonJS modules and ECMAScript modules.

By default, Node.js will treat the following as CommonJS modules:

• Files with a .cjs extension;

• Files with a .js extension when the nearest parent package.json filecontains a top-level field "type" with a value of "commonjs".

• Files with a .js extension or without an extension, when the nearest parentpackage.json file doesn't contain a top-level field "type" or there isno package.json in any parent folder; unless the file contains syntax thaterrors unless it is evaluated as an ES module. Package authors should includethe "type" field, even in packages where all sources are CommonJS. Beingexplicit about the type of the package will make things easier for buildtools and loaders to determine how the files in the package should beinterpreted.

• Files with an extension that is not .mjs, .cjs, .json, .node, or .js(when the nearest parent package.json file contains a top-level field"type" with a value of "module", those files will be recognized asCommonJS modules only if they are being included via require(), not whenused as the command-line entry point of the program).

See Determining module system for more details.

Calling require() always use the CommonJS module loader. Calling import()always use the ECMAScript module loader.

Accessing the main module#

When a file is run directly from Node.js, require.main is set to itsmodule. That means that it is possible to determine whether a file has beenrun directly by testing require.main === module.

For a file foo.js, this will be true if run via node foo.js, butfalse if run by require('./foo').

When the entry point is not a CommonJS module, require.main is undefined,and the main module is out of reach.

Package manager tips#

The semantics of the Node.js require() function were designed to be generalenough to support reasonable directory structures. Package manager programssuch as dpkg, rpm, and npm will hopefully find it possible to buildnative packages from Node.js modules without modification.

In the following, we give a suggested directory structure that could work:

Let's say that we wanted to have the folder at/usr/lib/node/<some-package>/<some-version> hold the contents of aspecific version of a package.

Packages can depend on one another. In order to install package foo, itmay be necessary to install a specific version of package bar. The barpackage may itself have dependencies, and in some cases, these may even collideor form cyclic dependencies.

Because Node.js looks up the realpath of any modules it loads (that is, itresolves symlinks) and then looks for their dependencies in node_modules folders,this situation can be resolved with the following architecture:

• /usr/lib/node/foo/1.2.3/: Contents of the foo package, version 1.2.3.
• /usr/lib/node/bar/4.3.2/: Contents of the bar package that foo dependson.
• /usr/lib/node/foo/1.2.3/node_modules/bar: Symbolic link to/usr/lib/node/bar/4.3.2/.
• /usr/lib/node/bar/4.3.2/node_modules/*: Symbolic links to the packages thatbar depends on.

Thus, even if a cycle is encountered, or if there are dependencyconflicts, every module will be able to get a version of its dependencythat it can use.

When the code in the foo package does require('bar'), it will get theversion that is symlinked into /usr/lib/node/foo/1.2.3/node_modules/bar.Then, when the code in the bar package calls require('quux'), it'll getthe version that is symlinked into/usr/lib/node/bar/4.3.2/node_modules/quux.

Furthermore, to make the module lookup process even more optimal, ratherthan putting packages directly in /usr/lib/node, we could put them in/usr/lib/node_modules/<name>/<version>. Then Node.js will not botherlooking for missing dependencies in /usr/node_modules or /node_modules.

In order to make modules available to the Node.js REPL, it might be useful toalso add the /usr/lib/node_modules folder to the $NODE_PATH environmentvariable. Since the module lookups using node_modules folders are allrelative, and based on the real path of the files making the calls torequire(), the packages themselves can be anywhere.

Loading ECMAScript modules using require()#

The .mjs extension is reserved for ECMAScript Modules.Currently, if the flag --experimental-require-module is not used, loadingan ECMAScript module using require() will throw a ERR_REQUIRE_ESMerror, and users need to use import() instead. SeeDetermining module system section for more inforegarding which files are parsed as ECMAScript modules.

If --experimental-require-module is enabled, and the ECMAScript module beingloaded by require() meets the following requirements:

• The module is fully synchronous (contains no top-level await); and
• One of these conditions are met:
  1. The file has a .mjs extension.
  2. The file has a .js extension, and the closest package.json contains "type": "module"
  3. The file has a .js extension, the closest package.json does not contain"type": "commonjs", and the module contains ES module syntax.

require() will load the requested module as an ES Module, and returnthe module namespace object. In this case it is similar to dynamicimport() but is run synchronously and returns the name space objectdirectly.

With the following ES Modules:

// distance.mjsexport function distance(a, b) { return (b.x - a.x) ** 2 + (b.y - a.y) ** 2; } 

// point.mjsclass Point { constructor(x, y) { this.x = x; this.y = y; }}export default Point; 

A CommonJS module can load them with require() under --experimental-detect-module:

const distance = require('./distance.mjs');console.log(distance);// [Module: null prototype] {// distance: [Function: distance]// }const point = require('./point.mjs');console.log(point);// [Module: null prototype] {// default: [class Point],// __esModule: true,// } 

For interoperability with existing tools that convert ES Modules into CommonJS,which could then load real ES Modules through require(), the returned namespacewould contain a __esModule: true property if it has a default export so thatconsuming code generated by tools can recognize the default exports in realES Modules. If the namespace already defines __esModule, this would not be added.This property is experimental and can change in the future. It should only be usedby tools converting ES modules into CommonJS modules, following existing ecosystemconventions. Code authored directly in CommonJS should avoid depending on it.

If the module being require()'d contains top-level await, or the modulegraph it imports contains top-level await,ERR_REQUIRE_ASYNC_MODULE will be thrown. In this case, users shouldload the asynchronous module using import().

If --experimental-print-required-tla is enabled, instead of throwingERR_REQUIRE_ASYNC_MODULE before evaluation, Node.js will evaluate themodule, try to locate the top-level awaits, and print their location tohelp users fix them.

All together#

To get the exact filename that will be loaded when require() is called, usethe require.resolve() function.

Putting together all of the above, here is the high-level algorithmin pseudocode of what require() does:

require(X) from module at path Y1. If X is a core module, a. return the core module b. STOP2. If X begins with '/' a. set Y to be the file system root3. If X begins with './' or '/' or '../' a. LOAD_AS_FILE(Y + X) b. LOAD_AS_DIRECTORY(Y + X) c. THROW "not found"4. If X begins with '#' a. LOAD_PACKAGE_IMPORTS(X, dirname(Y))5. LOAD_PACKAGE_SELF(X, dirname(Y))6. LOAD_NODE_MODULES(X, dirname(Y))7. THROW "not found"MAYBE_DETECT_AND_LOAD(X)1. If X parses as a CommonJS module, load X as a CommonJS module. STOP.2. Else, if `--experimental-require-module` is enabled, and the source code of X can be parsed as ECMAScript module using <a href="esm.md#resolver-algorithm-specification">DETECT_MODULE_SYNTAX defined in the ESM resolver</a>, a. Load X as an ECMAScript module. STOP.3. THROW the SyntaxError from attempting to parse X as CommonJS in 1. STOP.LOAD_AS_FILE(X)1. If X is a file, load X as its file extension format. STOP2. If X.js is a file, a. Find the closest package scope SCOPE to X. b. If no scope was found 1. MAYBE_DETECT_AND_LOAD(X.js) c. If the SCOPE/package.json contains "type" field, 1. If the "type" field is "module", load X.js as an ECMAScript module. STOP. 2. If the "type" field is "commonjs", load X.js as an CommonJS module. STOP. d. MAYBE_DETECT_AND_LOAD(X.js)3. If X.json is a file, load X.json to a JavaScript Object. STOP4. If X.node is a file, load X.node as binary addon. STOPLOAD_INDEX(X)1. If X/index.js is a file a. Find the closest package scope SCOPE to X. b. If no scope was found, load X/index.js as a CommonJS module. STOP. c. If the SCOPE/package.json contains "type" field, 1. If the "type" field is "module", load X/index.js as an ECMAScript module. STOP. 2. Else, load X/index.js as an CommonJS module. STOP.2. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP3. If X/index.node is a file, load X/index.node as binary addon. STOPLOAD_AS_DIRECTORY(X)1. If X/package.json is a file, a. Parse X/package.json, and look for "main" field. b. If "main" is a falsy value, GOTO 2. c. let M = X + (json main field) d. LOAD_AS_FILE(M) e. LOAD_INDEX(M) f. LOAD_INDEX(X) DEPRECATED g. THROW "not found"2. LOAD_INDEX(X)LOAD_NODE_MODULES(X, START)1. let DIRS = NODE_MODULES_PATHS(START)2. for each DIR in DIRS: a. LOAD_PACKAGE_EXPORTS(X, DIR) b. LOAD_AS_FILE(DIR/X) c. LOAD_AS_DIRECTORY(DIR/X)NODE_MODULES_PATHS(START)1. let PARTS = path split(START)2. let I = count of PARTS - 13. let DIRS = []4. while I >= 0, a. if PARTS[I] = "node_modules" CONTINUE b. DIR = path join(PARTS[0 .. I] + "node_modules") c. DIRS = DIR + DIRS d. let I = I - 15. return DIRS + GLOBAL_FOLDERSLOAD_PACKAGE_IMPORTS(X, DIR)1. Find the closest package scope SCOPE to DIR.2. If no scope was found, return.3. If the SCOPE/package.json "imports" is null or undefined, return.4. let MATCH = PACKAGE_IMPORTS_RESOLVE(X, pathToFileURL(SCOPE), ["node", "require"]) <a href="esm.md#resolver-algorithm-specification">defined in the ESM resolver</a>.5. RESOLVE_ESM_MATCH(MATCH).LOAD_PACKAGE_EXPORTS(X, DIR)1. Try to interpret X as a combination of NAME and SUBPATH where the name may have a @scope/ prefix and the subpath begins with a slash (`/`).2. If X does not match this pattern or DIR/NAME/package.json is not a file, return.3. Parse DIR/NAME/package.json, and look for "exports" field.4. If "exports" is null or undefined, return.5. let MATCH = PACKAGE_EXPORTS_RESOLVE(pathToFileURL(DIR/NAME), "." + SUBPATH, `package.json` "exports", ["node", "require"]) <a href="esm.md#resolver-algorithm-specification">defined in the ESM resolver</a>.6. RESOLVE_ESM_MATCH(MATCH)LOAD_PACKAGE_SELF(X, DIR)1. Find the closest package scope SCOPE to DIR.2. If no scope was found, return.3. If the SCOPE/package.json "exports" is null or undefined, return.4. If the SCOPE/package.json "name" is not the first segment of X, return.5. let MATCH = PACKAGE_EXPORTS_RESOLVE(pathToFileURL(SCOPE), "." + X.slice("name".length), `package.json` "exports", ["node", "require"]) <a href="esm.md#resolver-algorithm-specification">defined in the ESM resolver</a>.6. RESOLVE_ESM_MATCH(MATCH)RESOLVE_ESM_MATCH(MATCH)1. let RESOLVED_PATH = fileURLToPath(MATCH)2. If the file at RESOLVED_PATH exists, load RESOLVED_PATH as its extension format. STOP3. THROW "not found" 

Caching#

Modules are cached after the first time they are loaded. This means (among otherthings) that every call to require('foo') will get exactly the same objectreturned, if it would resolve to the same file.

Provided require.cache is not modified, multiple calls to require('foo')will not cause the module code to be executed multiple times. This is animportant feature. With it, "partially done" objects can be returned, thusallowing transitive dependencies to be loaded even when they would cause cycles.

To have a module execute code multiple times, export a function, and call thatfunction.

Module caching caveats#

Modules are cached based on their resolved filename. Since modules may resolveto a different filename based on the location of the calling module (loadingfrom node_modules folders), it is not a guarantee that require('foo') willalways return the exact same object, if it would resolve to different files.

Additionally, on case-insensitive file systems or operating systems, differentresolved filenames can point to the same file, but the cache will still treatthem as different modules and will reload the file multiple times. For example,require('./foo') and require('./FOO') return two different objects,irrespective of whether or not ./foo and ./FOO are the same file.

Built-in modules#

Node.js has several modules compiled into the binary. These modules aredescribed in greater detail elsewhere in this documentation.

The built-in modules are defined within the Node.js source and are located in thelib/ folder.

Built-in modules can be identified using the node: prefix, in which caseit bypasses the require cache. For instance, require('node:http') willalways return the built in HTTP module, even if there is require.cache entryby that name.

Some built-in modules are always preferentially loaded if their identifier ispassed to require(). For instance, require('http') will alwaysreturn the built-in HTTP module, even if there is a file by that name. The listof built-in modules that can be loaded without using the node: prefix is exposedas module.builtinModules.

Built-in modules with mandatory node: prefix#

When being loaded by require(), some built-in modules must be requested with thenode: prefix. This requirement exists to prevent newly introduced built-inmodules from having a conflict with user land packages that already havetaken the name. Currently the built-in modules that requires the node: prefix are:

• node:sea
• node:test
• node:test/reporters

Cycles#

When there are circular require() calls, a module might not have finishedexecuting when it is returned.

Consider this situation:

a.js:

console.log('a starting');exports.done = false;const b = require('./b.js');console.log('in a, b.done = %j', b.done);exports.done = true;console.log('a done'); 

b.js:

console.log('b starting');exports.done = false;const a = require('./a.js');console.log('in b, a.done = %j', a.done);exports.done = true;console.log('b done'); 

main.js:

console.log('main starting');const a = require('./a.js');const b = require('./b.js');console.log('in main, a.done = %j, b.done = %j', a.done, b.done); 

When main.js loads a.js, then a.js in turn loads b.js. At thatpoint, b.js tries to load a.js. In order to prevent an infiniteloop, an unfinished copy of the a.js exports object is returned to theb.js module. b.js then finishes loading, and its exports object isprovided to the a.js module.

By the time main.js has loaded both modules, they're both finished.The output of this program would thus be:

$ node main.jsmain startinga startingb startingin b, a.done = falseb donein a, b.done = truea donein main, a.done = true, b.done = true 

Careful planning is required to allow cyclic module dependencies to workcorrectly within an application.

File modules#

If the exact filename is not found, then Node.js will attempt to load therequired filename with the added extensions: .js, .json, and finally.node. When loading a file that has a different extension (e.g. .cjs), itsfull name must be passed to require(), including its file extension (e.g.require('./file.cjs')).

.json files are parsed as JSON text files, .node files are interpreted ascompiled addon modules loaded with process.dlopen(). Files using any otherextension (or no extension at all) are parsed as JavaScript text files. Refer tothe Determining module system section to understand what parse goal will beused.

A required module prefixed with '/' is an absolute path to the file. Forexample, require('/home/marco/foo.js') will load the file at/home/marco/foo.js.

A required module prefixed with './' is relative to the file callingrequire(). That is, circle.js must be in the same directory as foo.js forrequire('./circle') to find it.

Without a leading '/', './', or '../' to indicate a file, the module musteither be a core module or is loaded from a node_modules folder.

If the given path does not exist, require() will throw aMODULE_NOT_FOUND error.

Folders as modules#

There are three ways in which a folder may be passed to require() asan argument.

The first is to create a package.json file in the root of the folder,which specifies a main module. An example package.json file mightlook like this:

{ "name" : "some-library", "main" : "./lib/some-library.js" } 

If this was in a folder at ./some-library, thenrequire('./some-library') would attempt to load./some-library/lib/some-library.js.

If there is no package.json file present in the directory, or if the"main" entry is missing or cannot be resolved, then Node.jswill attempt to load an index.js or index.node file out of thatdirectory. For example, if there was no package.json file in the previousexample, then require('./some-library') would attempt to load:

• ./some-library/index.js
• ./some-library/index.node

If these attempts fail, then Node.js will report the entire module as missingwith the default error:

Error: Cannot find module 'some-library' 

In all three above cases, an import('./some-library') call would result in aERR_UNSUPPORTED_DIR_IMPORT error. Using package subpath exports orsubpath imports can provide the same containment organization benefits asfolders as modules, and work for both require and import.

Loading from node_modules folders#

If the module identifier passed to require() is not abuilt-in module, and does not begin with '/', '../', or'./', then Node.js starts at the directory of the current module, andadds /node_modules, and attempts to load the module from that location.Node.js will not append node_modules to a path already ending innode_modules.

If it is not found there, then it moves to the parent directory, and soon, until the root of the file system is reached.

For example, if the file at '/home/ry/projects/foo.js' calledrequire('bar.js'), then Node.js would look in the following locations, inthis order:

• /home/ry/projects/node_modules/bar.js
• /home/ry/node_modules/bar.js
• /home/node_modules/bar.js
• /node_modules/bar.js

This allows programs to localize their dependencies, so that they do notclash.

It is possible to require specific files or sub modules distributed with amodule by including a path suffix after the module name. For instancerequire('example-module/path/to/file') would resolve path/to/filerelative to where example-module is located. The suffixed path follows thesame module resolution semantics.

Loading from the global folders#

If the NODE_PATH environment variable is set to a colon-delimited listof absolute paths, then Node.js will search those paths for modules if theyare not found elsewhere.

On Windows, NODE_PATH is delimited by semicolons (;) instead of colons.

NODE_PATH was originally created to support loading modules fromvarying paths before the current module resolution algorithm was defined.

NODE_PATH is still supported, but is less necessary now that the Node.jsecosystem has settled on a convention for locating dependent modules.Sometimes deployments that rely on NODE_PATH show surprising behaviorwhen people are unaware that NODE_PATH must be set. Sometimes amodule's dependencies change, causing a different version (or even adifferent module) to be loaded as the NODE_PATH is searched.

Additionally, Node.js will search in the following list of GLOBAL_FOLDERS:

• 1: $HOME/.node_modules
• 2: $HOME/.node_libraries
• 3: $PREFIX/lib/node

Where $HOME is the user's home directory, and $PREFIX is the Node.jsconfigured node_prefix.

These are mostly for historic reasons.

It is strongly encouraged to place dependencies in the local node_modulesfolder. These will be loaded faster, and more reliably.

The module wrapper#

Before a module's code is executed, Node.js will wrap it with a functionwrapper that looks like the following:

(function(exports, require, module, __filename, __dirname) {// Module code actually lives in here}); 

By doing this, Node.js achieves a few things:

• It keeps top-level variables (defined with var, const, or let) scoped tothe module rather than the global object.
• It helps to provide some global-looking variables that are actually specificto the module, such as:
  • The module and exports objects that the implementor can use to exportvalues from the module.
  • The convenience variables __filename and __dirname, containing themodule's absolute filename and directory path.

The module scope#

__dirname#

Added in: v0.1.27

• <string>

The directory name of the current module. This is the same as thepath.dirname() of the __filename.

Example: running node example.js from /Users/mjr

console.log(__dirname);// Prints: /Users/mjrconsole.log(path.dirname(__filename));// Prints: /Users/mjr 

__filename#

Added in: v0.0.1

• <string>

The file name of the current module. This is the current module file's absolutepath with symlinks resolved.

For a main program this is not necessarily the same as the file name used in thecommand line.

See __dirname for the directory name of the current module.

Examples:

Running node example.js from /Users/mjr

console.log(__filename);// Prints: /Users/mjr/example.jsconsole.log(__dirname);// Prints: /Users/mjr 

Given two modules: a and b, where b is a dependency ofa and there is a directory structure of:

• /Users/mjr/app/a.js
• /Users/mjr/app/node_modules/b/b.js

References to __filename within b.js will return/Users/mjr/app/node_modules/b/b.js while references to __filename withina.js will return /Users/mjr/app/a.js.

exports#

Added in: v0.1.12

• <Object>

A reference to the module.exports that is shorter to type.See the section about the exports shortcut for details on when to useexports and when to use module.exports.

module#

Added in: v0.1.16

• <module>

A reference to the current module, see the section about themodule object. In particular, module.exports is used for defining whata module exports and makes available through require().

require(id)#

Added in: v0.1.13

• id <string> module name or path
• Returns: <any> exported module content

Used to import modules, JSON, and local files. Modules can be importedfrom node_modules. Local modules and JSON files can be imported usinga relative path (e.g. ./, ./foo, ./bar/baz, ../foo) that will beresolved against the directory named by __dirname (if defined) orthe current working directory. The relative paths of POSIX style are resolvedin an OS independent fashion, meaning that the examples above will work onWindows in the same way they would on Unix systems.

// Importing a local module with a path relative to the `__dirname` or current// working directory. (On Windows, this would resolve to .\path\myLocalModule.)const myLocalModule = require('./path/myLocalModule');// Importing a JSON file:const jsonData = require('./path/filename.json');// Importing a module from node_modules or Node.js built-in module:const crypto = require('node:crypto'); 

require.cache#

Added in: v0.3.0

• <Object>

Modules are cached in this object when they are required. By deleting a keyvalue from this object, the next require will reload the module.This does not apply to native addons, for which reloading will result in anerror.

Adding or replacing entries is also possible. This cache is checked beforebuilt-in modules and if a name matching a built-in module is added to the cache,only node:-prefixed require calls are going to receive the built-in module.Use with care!

const assert = require('node:assert');const realFs = require('node:fs');const fakeFs = {};require.cache.fs = { exports: fakeFs };assert.strictEqual(require('fs'), fakeFs);assert.strictEqual(require('node:fs'), realFs); 

require.extensions#

Added in: v0.3.0Deprecated since: v0.10.6

• <Object>

Instruct require on how to handle certain file extensions.

Process files with the extension .sjs as .js:

require.extensions['.sjs'] = require.extensions['.js']; 

Deprecated. In the past, this list has been used to load non-JavaScriptmodules into Node.js by compiling them on-demand. However, in practice, thereare much better ways to do this, such as loading modules via some other Node.jsprogram, or compiling them to JavaScript ahead of time.

Avoid using require.extensions. Use could cause subtle bugs and resolving theextensions gets slower with each registered extension.

require.main#

Added in: v0.1.17

• <module> | <undefined>

The Module object representing the entry script loaded when the Node.jsprocess launched, or undefined if the entry point of the program is not aCommonJS module.See "Accessing the main module".

In entry.js script:

console.log(require.main); 

node entry.js 

Module { id: '.', path: '/absolute/path/to', exports: {}, filename: '/absolute/path/to/entry.js', loaded: false, children: [], paths: [ '/absolute/path/to/node_modules', '/absolute/path/node_modules', '/absolute/node_modules', '/node_modules' ] } 

require.resolve(request[, options])#

• request <string> The module path to resolve.
• options <Object>
  • paths <string[]> Paths to resolve module location from. If present, thesepaths are used instead of the default resolution paths, with the exceptionof GLOBAL_FOLDERS like $HOME/.node_modules, which arealways included. Each of these paths is used as a starting point forthe module resolution algorithm, meaning that the node_modules hierarchyis checked from this location.
• Returns: <string>

Use the internal require() machinery to look up the location of a module,but rather than loading the module, just return the resolved filename.

If the module can not be found, a MODULE_NOT_FOUND error is thrown.

require.resolve.paths(request)#

Added in: v8.9.0

• request <string> The module path whose lookup paths are being retrieved.
• Returns: <string[]> | <null>

Returns an array containing the paths searched during resolution of request ornull if the request string references a core module, for example http orfs.

The module object#

Added in: v0.1.16

• <Object>

In each module, the module free variable is a reference to the objectrepresenting the current module. For convenience, module.exports isalso accessible via the exports module-global. module is not actuallya global but rather local to each module.

module.children#

Added in: v0.1.16

• <module[]>

The module objects required for the first time by this one.

module.exports#

Added in: v0.1.16

• <Object>

The module.exports object is created by the Module system. Sometimes this isnot acceptable; many want their module to be an instance of some class. To dothis, assign the desired export object to module.exports. Assigningthe desired object to exports will simply rebind the local exports variable,which is probably not what is desired.

For example, suppose we were making a module called a.js:

const EventEmitter = require('node:events');module.exports = new EventEmitter();// Do some work, and after some time emit// the 'ready' event from the module itself.setTimeout(() => { module.exports.emit('ready');}, 1000); 

Then in another file we could do:

const a = require('./a');a.on('ready', () => { console.log('module "a" is ready');}); 

Assignment to module.exports must be done immediately. It cannot bedone in any callbacks. This does not work:

x.js:

setTimeout(() => { module.exports = { a: 'hello' };}, 0); 

y.js:

const x = require('./x');console.log(x.a); 

exports shortcut#

Added in: v0.1.16

The exports variable is available within a module's file-level scope, and isassigned the value of module.exports before the module is evaluated.

It allows a shortcut, so that module.exports.f = ... can be written moresuccinctly as exports.f = .... However, be aware that like any variable, if anew value is assigned to exports, it is no longer bound to module.exports:

module.exports.hello = true; // Exported from require of moduleexports = { hello: false }; // Not exported, only available in the module 

When the module.exports property is being completely replaced by a newobject, it is common to also reassign exports:

module.exports = exports = function Constructor() { // ... etc.}; 

To illustrate the behavior, imagine this hypothetical implementation ofrequire(), which is quite similar to what is actually done by require():

function require(/* ... */) { const module = { exports: {} }; ((module, exports) => { // Module code here. In this example, define a function. function someFunc() {} exports = someFunc; // At this point, exports is no longer a shortcut to module.exports, and // this module will still export an empty default object. module.exports = someFunc; // At this point, the module will now export someFunc, instead of the // default object. })(module, module.exports); return module.exports;} 

module.filename#

Added in: v0.1.16

• <string>

The fully resolved filename of the module.

module.id#

Added in: v0.1.16

• <string>

The identifier for the module. Typically this is the fully resolvedfilename.

module.isPreloading#

Added in: v15.4.0, v14.17.0

• Type: <boolean> true if the module is running during the Node.js preloadphase.

module.loaded#

Added in: v0.1.16

• <boolean>

Whether or not the module is done loading, or is in the process ofloading.

module.parent#

Added in: v0.1.16Deprecated since: v14.6.0, v12.19.0

• <module> | <null> | <undefined>

The module that first required this one, or null if the current module is theentry point of the current process, or undefined if the module was loaded bysomething that is not a CommonJS module (E.G.: REPL or import).

module.path#

Added in: v11.14.0

• <string>

The directory name of the module. This is usually the same as thepath.dirname() of the module.id.

module.paths#

Added in: v0.4.0

• <string[]>

The search paths for the module.

module.require(id)#

Added in: v0.5.1

• id <string>
• Returns: <any> exported module content

The module.require() method provides a way to load a module as ifrequire() was called from the original module.

In order to do this, it is necessary to get a reference to the module object.Since require() returns the module.exports, and the module is typicallyonly available within a specific module's code, it must be explicitly exportedin order to be used.

The Module object#

This section was moved toModules: module core module.

• module.builtinModules
• module.createRequire(filename)
• module.syncBuiltinESMExports()

Source map v3 support#

This section was moved toModules: module core module.

• module.findSourceMap(path)
• Class: module.SourceMap
  • new SourceMap(payload)
  • sourceMap.payload
  • sourceMap.findEntry(lineNumber, columnNumber)