Python-like class sugar. No more "var that = this"!
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Self — Python inspired class sugar!

Why another OOP abstraction?

Self is class-based sugar inspired from Python syntax that's perfect for continuation-passing style. No more var this = that;! The implicit this variable is changed to an explicit self variable that your inner functions inherit. Self plays nicely with existing prototypal, and Backbone OOP.

var Timer = Self(EventEmitter, {
    count: 0,
    initialize: function (self, interval) {;

        setInterval(function () {
        }, interval);
    tick: function (self) {
        self.count += 1;
        self.emit('tick', self.count);


Development Version (0.2.1) — 6.1 KiB, uncompressed with comments.

Production Version (0.2.1) — 695 bytes, minified and gzipped.



To construct a base class, pass in a class definition to Self(...). The constructed class may be extended further by calling with <Class>.extend(...) method with a subclass definition. A class definition is an object containing properties and methods. Attached to every class is a __super__ property that points the parent class's prototype.

var Self = require('self');

var Animal = Self({

var Dog = Animal.extend({

var Beagle = Dog.extend({

Beagle.__super__ === Dog.prototype; // true

For JSLint compliance, a base class can be created using Self.extend(...).

var Animal = Self.extend({


The constructor for a class is the initialize method. Inside the constructor, parent and mixin constructors can be called. The new keyword may be omitted when instantiating an object.

var Name = Self({
    name_prefix: 'Sir',
    initialize: function (self, name) {
        self._name = name;
    name: function (self, name) {
        if (typeof name !== 'undefined') {
            self._name = name;
        return self.name_prefix + ' ' +;

var NameAge = Name.extend({
    initialize: function (self, name, age) {, name);
        self.age = age;
    age: function (self, age) {
        if (typeof age !== 'undefined') {
            self._age = age;
        return self.age;

var name = new Name(),
    name_age = NameAge();


Mixins can be used for multiple inheritance. To mixin a object of properties (not a class), call <Class>.mixin(object). When mixing in, only properties not already in the existing class will be copied in.

var Foo = Self({
    _foo: 'foo',
    initialize: function (self) {
        console.log('Foo has been mixed in to: ' + + '!');
    foo: function (self, foo) {
        if (typeof foo !== 'undefined') {
            self._foo = foo;
        return self._foo;

var Bar = Self({
    initialize: function (self) {;


Integrating With Other Forms of OOP

Prototypal OOP

A prototype can be manually wrapped with Self.create.

var EventEmitter = Self.create(require('events').EventEmitter);

Or use the shorthand and pass your base prototype as the first parameter in your class definition.

var Foobar = Self(EventEmitter, {
    initialize: function (self) {; // Calls EventEmitter's constructor


var MyModel = Self(Backbone.Model, {
    initialize: function (self, attr, opts) {, attr, opts);


Since Self.js wraps every method with a function that unshifts the context onto your method's arguments, there is overhead. Yo u will have to weigh the performance impact vs the convenience of an explicit self variable.

For me, an empty Self method is 2 orders of magnitude slower than an empty prototypal method. Keep in mind this overhead may be negligible compared to the time it takes to run the code in your method. Below are the actual timings of calling those methods on my machine.

  • With Self — 6 nanoseconds/call
  • Without Self — 610 nanoseconds/call

To run these benchmarks yourself, clone this project and run: npm install -d && node ./benchmarks.js


It should be possible to macro Self methods in-place (only in Node.js), thus removing the overhead of wrapping every method. If anyone is interested in this, please let me know and we can investigate it!