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Utility that compiles CommonJS (NodeJS) modules into a single JavaScript file suitable for the browser

CommonJS Compiler


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cjsc is a JavaScript transpiler that makes your CommonJS modules suitable for in-browser use. While every AMD-module results in a separate HTTP request and therefore badly affects page response time, cjsc, instead, combines all the acting modules in a single file (optionally compressed).

Comparing to the alternatives Browserify and Webpack, cjsc is much lighter and easier to configure. It's not a multipurpose tool. While Browserify attempts to bring node.js to the browser and Webpack to bundle as many formats as possible, cjsc is fully designated for a single task - to make CommonJS modules available in-browser. And it does the task pretty well.


  • Does not bring into your production code any additional library
  • Works fine with UMD modules (including jQuery, Backbone, Underscore and others)
  • Allows exporting globals of 3rd party libraries without intervention in their code
  • Supports source maps
  • Supports JavaScript templates ( Mustache, Handlebars, Underscore and others )
  • Produces a string out of (multiline) non-JS external text file
  • Provides transformation plugin API
  • Supports Browserify transformers
  • Supports Babel.js transformation

How cjsc works


How to install

Install nodejs/npm

cjsc utilizes nodejs and its package manager (NPM). If don't have these tools yet installed, you can find details on

Install cjsc


npm i cjsc --save-dev

or globally:

sudo npm i cjsc -g

Note: in this case npm creates a symlink /usr/bin/cjsc

Getting Started

Let's define a few CommonJS modules (


console.log( "main.js running..." );
console.log( "Imported name in main.js is `%s`", require( "./lib/dep1" ).name );
console.log( "Getting imported object from the cache:" );
console.log( " imported name in main.js is still `%s`", require( "./lib/dep1" ).name );


console.log( "dep1.js running..." );
console.log( " it has __diname = `%s`", __dirname );
console.log( " it has __filename = `%s`", __filename );
console.log( "Imported name in dep1.js is `%s`", require( "./dep2" ).name ); = "dep1";


console.log( "dep2.js running..." ); = "dep2";

Now we can compile the modules:

cjsc main.js -o script.js

As we execute script.js we get the following output:

main.js running...
dep1.js running...
 it has __diname = `.../demo/lib`
 it has __filename = `.../demo/lib/dep1.js`
dep2.js running...
Imported name in dep1.js is `dep2`
Imported name in main.js is `dep1`
Getting imported object from the cache:
 imported name in main.js is still `dep1`

Using CommonJS Compiler in the command line

 Usage: cjsc <src-path> <dest-path>
    <src-path> - source filename (e.g. main.js)
    --output, -o
        destination filename for compiled code
        example: <dest-path>, -o=<dest-path>
    --minify, -M
        minify the output file
    --config, -C
        specify a configuration JSON file
        example: --config=<file>
    --transform, -t
        use a transform module on top-level files.
        example: --transform=[MODULE --opt]
    --plugin, -p
        register MODULE as a plugin
        example: --plugin=MODULE
        specify an output file where to generate source map. Use "*" automatic naming
        example: --source-map=<file/pattern>
        the path to the source map to be added in.
        example: --source-map-url=<url>
        the path to the original source to be included in the source map.
        example: --source-map-root=<path>
        preserve copyright comments in the output.
        debug mode.
    --help, -h
        displays this help screen
Passing arguments to transforms:
  For -t you may use subarg syntax to pass options to the
  transforms or plugin function as the second parameter. For example:
    -t [ foo --x 3 --beep '{ a: 1 }' ]
  will call the `foo` transform for each applicable file by calling:
    foo( file, { x: 3, beep: '{ a: 1 }' } )

Compile main-module.js into build.js:

./cjsc main-module.js -o build.js


node cjsc.js main-module.js -o build.js

Compile main-module.js into build.js and generate source map

./cjsc main-module.js -o build.js  --source-map=build/ --source-map-url=http://localhost/

or the following options for automatic naming

./cjsc main-module.js -o build.js  --source-map=*.map

or this way to explicitly specify the path to sources relative to the source map

./cjsc main-module.js -o build.js  --source-map=build/*.map --source-map-root=../src


  • --source-map is a source map file path relative to the project directory (the directory where cjsc is running)
  • --source-map-url by default is "." and means the same path as source map file
  • --source-map-root is sources path relative to the source map file. For instance: sources are in <project>/src, build is in <project>/build. So specify --source-map-root=../src to let the browser know that it must look for mapped source file in ../src/**/file.js relative to the source map path.

Now breakpoints and console messages mapped to the original sources Source mapping example

Compile main-module.js into build.js and minify build.js

./cjsc main-module.js -o build.js -M

With a banner

./cjsc main-module.js -o build.js -M --banner="/*! pkg v.0.0.1 */"

File Modules

The module object

Every module has exposed module variable that references to an object representing the module. Like in NodeJS the object has following structure:

  • {string} - The identifier for the module.
  • module.filename {string} - The fully resolved filename to the module.
  • module.loaded {boolean} - Whether or not the module is done loading.
  • module.parent {Object} - The module that required this one.
  • module.children {Object[]} - The module objects required by this one


Caching goes the same as in nodejs. Modules are cached after the first time they are loaded. So every call to require('foo') returns exactly the same object, if it refers to the same file.

Multiple calls to require('foo') don't execute the module code multiple times.

Setting up Grunt task


     cjsc: {
      development: {
                options: {
                    minify: true
        files: {
          "<path>/compiled.js" : "<path>/source.js"


"devDependencies": {
    "grunt-cjsc": ">=1.0.0"

Please find details at

How to configure dependency

You can configure your dependencies in a JSON file. E.g. config.json:

    "<dependency-name>": {
        "path": "<dependency-path>",
        "globalProperty": "<global-property>",
        exports: [ "<variable>", "<variable>" ],
        require: [ "<dependency-name>", "<dependency-name>" ]


    "<dependency-name>": {
        "path": "<dependency-path>",
        "globalProperty": "<global-property>",
        exports: "<variable>",
        require: "<dependency-name>"

To enable the configuration use --config option:

node cjsc main.js build.js --config=config.json

Passing plugin configurations:

  "ver": 1,
  "modules": {
    "<dependency-name>": {},
    "<dependency-name>": {}
  "plugins": [
      "plugin": "<pkg-name>",
      "targets":  {
        "<target>": [{
          /* options object */

How to make module of a globally exposed variable


    "jQuery": {
        "globalProperty": "jQuery"


var $ = require( "jQuery" );
// $ - is a reference to globally exposed jQuery instance (assuming window.jQuery si defined outside this module) 
console.log( $( window ) );


node cjsc main.js build.js --config=config.json

How to make modules of jQuery and its plugins


    "jQuery": {
        "path": "./vendors/jquery-2.1.0.min.js"
    "placeholder": {
        "path": "./vendors/jquery.placeholder.js",
        "require": "jQuery",
        "exports": "jQuery"


// Obtain jQuery as UMD-module 
var $ = require( "jQuery" );
// Attach plugin to jQuery 
require( "placeholder" );
console.log( $.fn.placeholder );


node cjsc main.js build.js --config=config.json

How to make modules of 3rd party libraries

Options #1:

// Load 3rd-party library and export the globals it exposes ("exp1" and "exp2") 
var exp1 = require( "./vendors/lib.js", "exp1", "exp2" ).exp1,
// Take the second exported object from the module cache 
        exp2 = require( "./vendors/lib.js" ).exp2;
console.log( "exp1", exp1 );
console.log( "exp2", exp2 );

Options #2:


    "lib": {
        "path": "./vendors/lib.js",
        "exports": [ "exp1", "exp2" ]


var lib = require( "lib" );
console.log( lib.exp1, lib.exp2 );


node cjsc main.js -o build.js --config=config.json

If 3rd party code exposes the only object, it can be done like that:


    "lib": {
        "path": "./vendors/lib.js",
        "exports": "exp1"

Note: The "path" must be relative to the project directory (where the compiler is running from)


var lib = require( "lib" );
// Exp1 
console.log( lib );

How to use Mustache templates

Template file: ./mustache/example.tpl

{{title}} spends {{calc}}

Module that uses the template

var mustache = require( "./mustache/mustache" ),
        tpl = require( "./mustache/example.tpl" ),
        view = {
            title: "Joe",
            calc: function () {
                return 2 + 4;
console.log( mustache.render( tpl, view ) );

How to use Handlebars templates

Template file: ./handlebarsjs/example.hbs

<div class="entry">
  <div class="body">

Module that uses the template

var handlebars = require( "./handlebarsjs/handlebars", "Handlebars" ).Handlebars,
        tpl = require( "./handlebarsjs/example.hbs" ),
        view = {
            title: "My New Post",
            body: "This is my first post!"
console.log( handlebars.compile( tpl )( view ) );

Supplied demos

# Generic flow
node cjsc.js -o /tmp/build.js demo/use-main-flow.js
node /tmp/build.js
# Access 3rd-party non-module in a module
node cjsc.js -o /tmp/build.js demo/use-3rd-party.js
node /tmp/build.js
# Non-module to compiled CommonJS
node cjsc.js -o /tmp/build.js demo/use-nonmodule.js
node /tmp/build.js
# UMD to compiled CommonJS
node cjsc.js -o /tmp/build.js demo/use-umd.js
node /tmp/build.js
# Backbone as a module
node cjsc.js -o /tmp/build.js demo/use-backbone.js
node /tmp/build.js
# Templating with Mustache
node cjsc.js -o /tmp/build.js demo/use-mustache.js
node /tmp/build.js
# Templating with Handlebars.js
node cjsc.js -o /tmp/build.js  demo/use-handlebars.js
node /tmp/build.js
# Source map usage demo
node cjsc.js -o demo/source-map/build.js demo/source-map/src/use-main-flow.js --source-map=demo/source-map/*.map --source-map-root=./src
# Config usage demo
node cjsc.js -o /tmp/build.js demo/use-config.js --config=./demo/config/config.json
# Browserify-plugin usage demo
npm install -g browserify-replace
node cjsc.js -o /tmp/build.js demo/use-browserify-replace.js -t [ browserify-replace \
                  --replace '{ "from": "\\$foo", "to": 42 }' \
                  --replace '{ "from": "\\$bar", "to": "quux" }' ]
# ES6 via Babel.js usage demo
node cjsc.js -o /tmp/build.js  demo/use-es6.es6 -t [ babelify --presets [ es2015 --sourceMapRelative ] ]
node /tmp/build.js

How to load the compiled files asynchronously

Loading dozens of atomic modules asynchronously usually slower then loading one compiled file. This is an advantage of Common JS compiler over AMD. However if you go with a huge compiled file, it would be efficient to split it into a few parts for async loading. It is a matter of balance: too many HTTP requires is bad for performance as well as too few. Here how I deal with it.

I inline into the page body tiny async loader Micro RequireJS (1.5K) and use it to load external libraries and compiled assets asynchronously:

<script type="text/javascript">
<?php include PATH_ROOT . "node_modules/micro-requirejs/rjs.min.js"; ?>
rjs.define( "/vendors/jquery/jquery-1.10.2.min.js", "jquery" );
rjs.define( "/vendors/picturefill/picturefill.min.js", "picturefill" );
rjs.define( "/build/js/app.js", "app" );
rjs.define( "/build/js/sub-app.js", "subapp" );
// Backbone requires jQuery during initialization
rjs.require([ "jquery" ], function(){
  rjs.define( "/vendors/exoskeleton/exoskeleton.min.js", "backbone" );

Then I specify in the source module what dependencies must be resolved before running the code depended on them:

global.rjs.require([ "jquery", "backbone" ], function(){
  var $ = require( "jquery" ),
      Backbone = require( "backbone" );

Bonus tricks

While debugging you can refer to the module name as __modulename:

console.log( __modulename + ": remote call [status=%s]", status );
// >> Lib/Api/Provider: remote call [status=ok] 


var cjsc = require( ".././cjsc-module" ),
    args = {
      targets: [ "./demo/use-main-flow.js", "/tmp/build.js" ],
      options: {
        debug: true,
        transform: [{
          target: pkgName,
          options: {
            foo: true
    config = {
      "foo": {
         "globalProperty": "foo"
cjsc( args, config, function( code ){
  console.log( "All done. Generated code:", code );

Plugin example

Plugin example

var through = require( "through2" );
/*  export a Browserify plugin  */
module.exports = function ( file, opts ) {
    /*  provide stream  */
    var code = "";
    return through.obj(function (buf, enc, next) {
        //  accumulate the code
        code += buf.toString("utf8");
    }, function ( next ) {
        // Get parameters for `replace` target
        // if command line has multiple `replace` targets, opts.replace is an array
        var params = global.JSON.parse( opts.replace );
        //  transform the code
        code = code.replace( cfg.from, );
        this.push( new Buffer( code ) );


node cjsc.js -o /tmp/build.js app.js -t [ plugin \
                  --replace '{ "from": "\\$foo", "to": 42 }' ]

Compiling to ES6(2015)

cjsc.js src/Js/app.js -t [ babelify --presets [ es2015 ] --sourceMapRelative ] -o ./build/app.js



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