ECMAScript 3 to 6 compatible Class definition
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src fixed problem with deep static copy in IE6 Nov 2, 2015
template version 0.1.0 Nov 2, 2014
.npmignore even more clean up and bumped version Jun 16, 2015
.travis.yml fixed travis problem Aug 24, 2015 mixins now support classes Apr 18, 2015
LICENSE.txt added support for Espruino engine Apr 20, 2015
Makefile fixed issues with uglify-js old May 30, 2018 Update about Classtrophobic Jan 14, 2017
package.json trying again May 30, 2018

es-class build status

Don't miss Classtrophobic!

which is a natural evolution of this project. It provides bare minimal functionality to deal with native classes without haveing ever any transpiler on its way.

A future proof, backward compatible, JavaScript class utility.

  • ES6 and ES7 friendly, through semantic extends and constructor plus other features
  • ES5 natively compatible granting that what you write is what you get
  • ES3 backward compatible, thanks to common minifiers that will make production code safe

Feel free to test all features related to this project, and please come back if your browser is not green.

via npm

npm install es-class It is suggested to install this globally as it's a very small script.

via cdn

Many thanks to cdnjs for hosting this script. Following an example on how to include it.

>/* ES-Class */</script>


Following a list of tested browsers split in Desktop and Mobile, plus a list of server/micro-controller side supported engines.


  • IE 6 or greater
  • Firefox 3 or greater
  • Chrome
  • Safari
  • Opera


  • Android 2 or greater
  • iOS 5 or greater
  • UC Browser and UC Mini
  • IE9 Mobile or greater
  • Opera Mini and Mobile
  • Blackberry OS 7 and OS 10
  • Kindle Fire
  • Ubuntu Phone
  • Bada
  • Xpress
  • webOS

Others (tested)

  • Espruino Pico
  • MIPS version of node for Arduino Yun
  • node.js 0.6+ and io.js every (so Raspberry PI and every other with node.js)
  • Duktape and Nashorn

If you actually know a hybrid (like Espruino) or ES3+ engine that does not work, please file a bug, thank you!


All features explained in the dedicated page.

Following a summary:

  • constructor to optionally define the implicit initializer per each instance
  • extends to optionally define a class or an object to inherit from
  • super to shortcut super methods invocation
  • with to attach lightweight traits / mixins enabling composition behind optional initializers per each mixin. Compatible with universal-mixin since version 1.3.0
  • static to define public static class constants, inherited if extended, without ever polluting the prototype
  • implements to perform light checks over expected implementations and warn eventually when something is missing

Features Example

This is an example of what's possible:

var Engineer = Class({
  extends: Person,
  with: [
  implements: [
  static: {
    SOFTWARE: 0,
  constructor: function (name, age, type) {
    this.super(name, age);
    this.type = type;

var me = new Engineer(
  'Mr. Andrea Giammarchi',

me instanceof Person; // true
me.type;              // Engineer.SOFTWARE

me.emit('work:start', {
  tasks: ['do this', 'do that']

ES6 Ready

Using Babel it is possible to make your code directly compatible down to ES5 or even ES3 without loosing the ability to debug in every platform without needing source-map. What you see is basically what you get.

// how you would write in native ES6
class B extends A {
  method(x, y) {
    return super.method(x, y);
  get value() {
    return super.value;
  set value(value) {
    super.value = value;

// how you would write in es-class
var B = Class({ extends: A,
  method(x, y) {
    return this.super(x, y);
  get value() {
    return this.super();
  set value(value) {
    return this.super(value);

A simple call to babel --whitelist=es6.arrowFunctions, f.js and the output will be way cleaner than any automation produced by the same transpiler.

Your output will be more readable and also probably faster at execution time.

ES7 Ready

Looking at the future, grouped static properties and lightweight traits are also in, giving the ability to compose classes through eventual traits initialization without being on the way after class definition.

var wheels = {
  init: function () {
    if (this instanceof Car) {
      this.frontWheels = 2;
      this.rearWheels = 2;
    } else {
      this.frontWheels = 1;
      this.rearWheels =
        this instanceof Tricycle ? 2 : 1;
  turn: function (where) {
    console.log('turning ' + where);

var engine = {
  hp: 120

var Car = Class({
  with: [

var c = new Car;
c.turn('left'); // trning left
c.hp;           // 80

Which File ?

You can also simply npm install -g es-class and use var Class = require('es-class'); whenever you need it.


MIT Style License