They all define the rules of modules, such as module identification, module dependency, module implementation, module external interface, module loading;

There are asynchronous, synchronous, pre-dependent, near-dependent, pre-execution, lazy execution, soft dependency, hard dependency, and support types of module objects.

CommonJS

Common JS Modules/1.0 specification, Summary, wiki

On the server or the local desktop application, the module format is defined.

Only object type modules are supported and loaded synchronously.

For example, module qux:

// filename: qux.js

// dependencies
var $ = require('jquery');

// methods
function foo(){};

// exposed public method (single)
module.exports = foo;

// filename: qux.js
var $ = require('jquery');
var _ = require('underscore');

// methods
function foo(){};    //    private because it's omitted from module.exports (see below)
function bar(){};    //    public because it's defined in module.exports
function baz(){};    //    public because it's defined in module.exports

// exposed public methods
module.exports = {
    bar: bar,
    baz: baz
};

AMD

Asynchronous Module Definition, Summary, Why AMD?

Asynchronous/Synchronous Loading

Support object, function, constructor, string, JSON and other types of modules.

Early implementation of AMD relies on pre-implementation and early execution

define(id?, dependencies?, factory);

For example, module qux:

// filename: qux.js
define(['jquery'], function ($) {
    // methods
    function foo(){};

    // exposed public methods
    return foo;
});

// filename: qux.js
define(['jquery', 'underscore'], function ($, _) {
    // methods
    function foo(){}; // private because it's not returned (see below)
    function bar(){}; // public because it's returned
    function baz(){}; // public because it's returned

    // exposed public methods
    return {
        bar: bar,
        baz: baz
    }
});

Compatible with CommonJS specification:

// filename: qux.js
define(function (require, exports, module) {
    // dependencies
    var $ = require('jquery');
    _ = require('underscore');

    // exposed public methods
    exports.foo= function () {}
});

CMD

Common Module Definition, Summary, Chinese

define(function(require,exports,module){...});

CMD implements dependency proximity and delays execution

UMD

Universal Module Definition

Identify the style of modules supported by the current environment and compatible with different loading specifications

// code from https://github.com/tangshuang/omd
(function(factory){
    "use strict";

    // change to your module name
    var NAME = 'omd';

    if(typeof define == 'function' && (define.cmd || define.amd)) { // amd & cmd
        define(function(require){
            var requires = {
                /**
                 * dependences: 
                 * 1. need to fill requires
                 * 2. use require, moudule name should be defined before
                 * 3. relative path is not allowed in cmd & amd mode
                 */
                // 'jquery' : require('jquery'),
                // 'bootstrap' : require('bootstrap')
            };
            var _require_ = function(key) {
                return requires[key];
            }
            return factory(_require_);
        });
    }
    else if(typeof module !== 'undefined' && typeof exports === 'object') { // nodejs
        module.exports = factory(require); // in node, require can be used everywhere generally
    }
    else { // none module
        this[NAME] = factory(function(key){
            return this[key];
        }.bind(this));
    }
}).call(this || (typeof window !== 'undefined' ? window : global),function(require){
    "use strict";

    // require('jquery');

    /**
     * use return object to export. i.e.
     * return {
        name : 'module name',
        init : function(opotions) {},
        destory : function() {}
     };
     */

});

(function (root, factory) {
    if (typeof define === 'function' && define.amd) {
        // AMD
        define(['jquery', 'underscore'], factory);
    } else if (typeof exports === 'object') {
        // Node, CommonJS-like
        module.exports = factory(require('jquery'), require('underscore'));
    } else {
        // Browser globals (root is window)
        root.returnExports = factory(root.jQuery, root._);
    }
}(this, function ($, _) {
    // methods
    function foo(){}; // private because it's not returned (see below)
    function bar(){}; // public because it's returned
    function baz(){}; // public because it's returned

    // exposed public methods
    return {
        bar: bar,
        baz: baz
    }
}));

ES6

import,export

Quote from and expand reading:

• Modules - CommonJS Spec Wiki
• Modules | Node.js Documentation
• Why Web Modules?
• David Calhoun: What is AMD, CommonJS, and UMD?
• Huang Xuan: JavaScript Module Loader
• Huang Xuan: A Seven-Day Talk on JavaScript Modularization
• Ruan Yifeng: Module Grammar - Introduction to ECMAScript 6
• Ruan Yifeng: Javascript Modular Programming
• Nuggets: A Brief History of JavaScript Modules
• Yubo: The History of Front-end Modular Development. seajs/seajs