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CommonJS modules for the browser

modules Build Status

Use CommonJS modules client-side in web applications

Getting started

Install via npm

npm install modules --save-dev

Add the middleware to your express or connect app

app.get('/module', require('modules').middleware({
	root: './component', // where modules live in the filesystem
	// ... other options

Add the client script to your html

<script src="/module/define.min.js" data-main="my-main-module"></script>

Mapping and Bundling

You can create bundles (files containing multiple modules), and/or map modules to urls outside of the conventional location.

Client-side, this mapping is handled with the data-urls attribute on the script tag, or with a call to define.url(). define.url(url, ids) maps a single url to all the modules at that url, and the data-urls attribute expects a JSON object with urls as keys, and arrays of module ids as the values.

define.url("url/of/bundle.js", [ "moduleid" ])

<script ... data-urls='{"bundle.js":["moduleid"]}'></script>

Server-side and at build time you can generate bundles with the following snippets:

// Generate a bundle with a specific set of modules included
	[ 'module1', 'module2' ],
	{ /* options */ }, // specify optional compression, etc.
	function(err, js, modified) {
		// js is a string containing the AMD-wrapped javascript for the modules
		// modified is the most recent modified date among the included modules

// Generate a bundle with all of the deep dependencies of the modules, excluding
//  the deep dependencies of another list of modules
	[ 'module1', 'module2' ], // include these and their deep dependencies
	[ 'module3', 'module4' ], // except any of these or their deep dependencies
	{ /* options */ },
	function(err, js, modified) {


In Browser

define.js or define.min.js

These scripts create the define function used to create a module environment in the browser. You can reference the file how ever you'd like; they are in the lib folder in the source code. However, the preferred way is to include a script tag pointing to the path the middleware is listening to, or to a bundle including define:

<script src="/path/to/define.min.js"></script>
  • define(id, dependencies?, factory) -- Define module id. id is required in this implementation. If the dependencies parameter is omitted, the factory will not be scanned for require() calls, [ 'require', 'exports', 'module' ] will be used instead. See the AMD wiki for details.
  • define.amd -- Object denoting AMD compatibility.


This is only useful to include first in a bundle that may be loaded before the define or define.min script has run. Usually the main bundle includes define.min and the shim is not needed.

  • define(id, dependencies?, factory) -- Saves the arguments for when define or define.min is loaded.
  • define.amd -- Object denoting AMD compatibility.

module scope

(inside the factory function)

See the CommonJS Module spec, the AMD spec, and Node.js modules

  • exports -- Alias for module.exports. An object to assign properties to in order to export values.
  • module -- An object representing this module.
  • module.children -- An array of module objects for the modules this one requires synchronously.
  • module.exports -- This object will be returned from require() calls for this module. Assign to this to export the value. Note if you assign to this property, the exports variable is not automatically updated.
  • module.filename -- Alias of uri. The url of the script containing this module.
  • module.loaded -- True if the module has already been defined.
  • module.parent -- The module object for the module that first required this module.
  • -- A string of slash separated terms identifying the module.
  • module.require() -- A require() function that always resolves relative ids against this module's id.
  • module.uri -- Alias of filename. The url of the script containing this module.
  • require(id) -- Returns the exports for the module identified. Throws an error if the module has not been loaded. id is a module id string.
  • require(ids, next) -- Asynchronously load the modules, require them, and pass them as arguments to the callback function next. ids may be a single id string, or an array of module id strings.
  • require.cache -- A store of all modules the system knows about. You may undefine a module by delete require.cache[]. Assigning to this property will have no effect.
  • require.main -- The module object of the module loaded by the data-main attribute of the define script.
  • require.resolve(id) -- Resolves a relative module id against this module's id, and returns the uri for that module.
  • require.toUrl(id) -- Similar to require.resolve(). See the AMD spec.
  •, ids) -- Tell require where to load specific modules. url is the url to request, and ids is an array of module ids that are defined by the file at the url.

In Node.js


modules = require('modules')

Provides middleware and functions to wrap and bundle your modules for use in the browser.

  • modules.dependencies(id, js, options?) -- Finds all literal synchronous require() calls in a module identified by id. js is the code for the module as a string. If options.absolute is true, the returned dependency ids are made absolute, otherwise they are returned as written in the code. Returns an array of module id strings. Note: this uses regular expressions instead of a parser. Comments are excluded. The function will miss any calls with a renamed require, or a variable instead of a string literal id.

  • modules.middleware(options?) -- Returns an express / connect middleware using the options passed in.

    • compress -- Defaults to false. If a function is specified, it will be passed a module object with id, filename, code, and modified properties as the first parameter, and a function as the second. It expects the function to be called with either an error or null in the first argument, and the compressed code as a string in the second. Example:

        compress:function(js, next) {
        	var UglifyJS = require('uglify-js');
        	js = UglifyJS.minify(js.code, { fromString:true });
        	next(null, js);
    • forbid Defaults to []. If the file path to a module matches an entry in this list, a 'Forbidden' error will be passed to the next error middleware. Entries can be a string module id (filename starts with entry), a regular expression (exp.test(filename)) or any object with a test function property (obj.test(filename)). Files outside of the root directory are always forbidden, unless they have been mapped. Mapped files are always allowed. Example:

        forbid: [
        	'server', /\.middleware\.js$/,
        	{ test:function(filename) {
        		return filename.slice(-3) === 'foo';
        	} }
    • encoding Defaults to 'utf8'. Encoding to read module files in.

    • map Defaults to {}. Map module ids to files in the filesystem. define, define.min, and define.shim will be mapped to their locations in lib unless explicitly mapped elsewhere. Relative paths are resolved against root. Values can also be functions Example:

        map: {
        	jquery: './vendor/jquery.min.js',
        	session: function(id, options) {
        		// figure out or generate the file for this user
        		return sessionFilename;
    • maxAge -- Defaults to undefined. Seconds the browser should cache the module code. If set, will be put in a Cache-Control: public, max-age= HTTP header.

    • nowrap Defaults to [ 'uris.json', /\.amd\.js$/i ]. If a module id matches an entry in this list, it is not wrapped with a define() call. Entries can be a string module id (entry === id), a regular expression (exp.test(id)) or any object with a test function property (obj.test(id)).

    • root -- Defaults to process.cwd(). Base path for modules in the filesystem.

    • translate Defaults to {}. Translate specific files into CommonJS modules. Object keys may be filenames, module ids, or file extensions. The functions are passed a module object, with id, filename, and buffer properties. Example:

        translate: {
        	html: function(module, options, next) {
        		var id =, // String
        			filename = module.filename, // String
        			content = module.buffer, // Buffer
        			_ = require('underscore');
        		content = content.toString('utf8');
        		next(null, 'exports.template = ' + _.template(content).source);

      If they do not match any keys in this option, modules are converted from Buffer to string with options.encoding.

  • modules.module(id, options?, next) -- Generate the client-side code for the module. id is a module id string. options are the same as for modules.middleware(). next(err, result) will be called when done. err is any error that may have occured, or null otherwise. result is an object with properties code, which is the browser javascript as a string, and modified, which is a Date of the last modified time on the source file.

  • modules.modules(ids, options?, next) -- Exactly like modules.module only ids is an array of module id strings, all of which are included in the resulting result.code. The result.modified is the most recent modified time among all of the source files loaded.


bundles = require('modules/lib/bundles')

Provides functions for bundling modules with their deep dependencies.

  • bundles.bundle(ids, exclude, options?, next) -- Generate a bundle including the browser code for all of the modules in the ids array and their deep dependencies, except exclude and all of their deep dependencies. ids and exclude are arrays of module id strings. options are the same as modules.middleware(). next is called when complete, with the same arguments as next in modules.module().
  • bundles.dependencies(ids, options?, next) -- Gets a list of ids and all of their deep dependencies. Modules need to be loaded in order to determine their dependencies, so modules.module() is called inside this method, with the options passed in. next(err, ids) is called when complete, with ids as an array of absolute module id strings.
  • bundles.expand(ids, exclude, options?, next) -- Gets a list just like bundles.dependencies(), only the ids in exclude and their deep dependencies are omitted from the list.

Client-Side Features

  • CommonJS Modules 1.1.1 implementation for in-browser use
  • module.require function similar to Node.js implementation
  • require(id, callback) for async a la require.js
  • Map module ids to arbirary uris

Server-Side Features

  • Middleware for express / connect
  • Create bundles of all the deep dependencies of a list of modules
  • Configure minification using your favorite compressor

Browser Support

  • IE 8+, Chrome, Firefox, Safari, Opera
  • IE Mobile, Chrome Mobile, Firefox Mobile, Safari Mobile, Opera Mobile

Basically, bugs reported in any common browser will get fixed. If you need to support IE6 or IE7, please use the last version to support them: v0.3.3.

Who and Why

modules was written by Andy VanWagoner (thetalecrafter).

Some of the motivation for this project can be found in this article.

  • If you like writing your modules in AMD, use require.js.
  • If you want the browser environment to be just like Node.js, use browserify.
  • If you want simple CommonJS in the browser, then modules is for you.