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Mochiscript is a superset of the JavaScript language that adds more Object-Oriented features such as: methods, inheritance, mixins, etc... What this means is that Mochiscript IS Javascript. Mochiscript currently supports Ruby on Rails 3.1 (via asset pipeline) and Node.js.

More on Mochiscript features and syntax here:


In Rails >3.1

In the Gemfile, add this line:

gem 'mochiscript'

In app/assets/javascripts/application.js, add mochiscript

//= require mochiscript

Now, you should be able to create ".ms" files and it'll be included as javascript using the new rails asset pipeline.

An example:

Create a simple mochiscript (app/assets/javascripts/

class Hello {
  function say() {

Now include it in application.js

//= require hello

Now on your page, you should be able to put this code in after your javascript include section:

  var obj = new Hello();

In Node.js

npm install mochiscript


export class Hello {
  function say() {

In main.js:

var Hello = require('./hello');
var obj   = new Hello();


Parsing a file:

ms-parse <filename>

Running an ms file:

ms-run <filename>

Compiling files in a directory:

ms-watch <src> <dest> <template>
  1. src: source directory with .ms files
  2. dest: destination directory to write .js files
  3. template file (optional). This will allow you to templatize mochiscript. Just make sure the file has "MOCHI" in it.

Mochiscript in the browser

Bootstrap File

Please include this file before requiring any mochiscript compiled file: mochiscript.js


Using connect/express:

var options = {
  src: "views",

More on Syntax

Mochiscript syntax is a superset of JavaScript's. This means that any JavaScript you write will run just fine in Mochiscript. Mochiscript simply adds extra features that make development life a little easier.

Object Oriented Features


Classes can be created with the "class" keyword. If you wish to have a custom initializer function, just include a method called "initialize".

class Hello {
  var defaultMessage = "Just say hello";

  function initialize(message) {
    this.message = message || this.defaultMessage;

  function say() {

var obj = new Hello("what's up?");


The method "initialize" is the default instance method used to instantiate an object (just like Ruby).

class Foo {
  function initialize(arg1, arg2) {
    this.args = [ arg1, arg2 ];
    console.log("Instance of Foo created!", arg1, arg2);

var foo = new Foo("hello", "world");


class Goodbye extends Hello {
  var defaultMessage = "Goodbye";
  function say() {


module World {
  function world() {

class HelloWorld extends Hello {
  include World;

Private Section

This is a little unorthodox part of Mochiscript which allows you to add a "closed" section that only methods in the scope of the class can access.

class MyClass {
  private {
    var CONSTANT_VAR = "constant";

  function initialize(data) { = data || CONSTANT_VAR;

Accessing "self"

A lot of times, you need access to the "this" object in a callback. The problem is that "this" often points to something else in a different context. The workaround is usually:

class Foo {
  var hello = "hello";
  function setup() {
    var self = this;
    $('.hello').click(#{ alert(self.hello) }); 

In mochiscript, it is no longer necessary to create a "self" variable. Its given to you in all methods:

class Foo {
  var hello = "hello";
  function setup() {
    $('.hello').click(#{ alert(self.hello) });

Syntactic Sugar

Shorthand Functions

There are two ways to use this feature:

var myFunct = #{ console.log($1) }; // prints out first argument (supports up to 3 args)
var myFunct = #(msg){ console.log(msg) };

Shorthand returns

[ 1, 2, 3 ].map(#{ => $1 + 1 });


var array = [ 'hello', 'world' ];
foreach (var word in array) {

// foreach with iterator
foreach (var word:i in array) {
  console.log(i, word);


var message = <<END;
  this is a lot of text

Enumerable Functions (experimental)

var greetings = [ 'hi', 'hello' ];
var mapped    = greetings#map { $1 + " there!" };
var some      = greetings#some { $1 == 'hi' };

Node-specific module exporters

Mochiscript has two helpers for exporting your files:

public class MyClass {


// equivalent to 
// exports.MyClass = MyClass;

Or make it the default export:

export class MyClass {


// equivalent to
// module.exports = MyClass;


  1. Jeff Su
  2. Hong Hao