class.js

Simple and efficient class inheritance based on John Resig's code ("Simple JavaScript Inheritance" and "Simple Class Instantiation").

Written for being used with node.js.

Installation

npm install class.js

Example

var Class = require('class.js');

// Create a class.

var A = Class({
    // Contructor's code should be put into init().
    init: function(x) {
        this.x = x;
    },
    f: function() {
        this.x += 2;
    }
});

// Instantiate.

var a = new A(7); // init(7) is called.

// This way is valid too, in case you accidentally forgot to write "new":

var a2 = A(7);

// Also, you have the magic "_parent()" method which allows you
// to call a method of the same name from the parent class.

// Let's create a child class.

var B = A.extend({
    init: function(x) {
        // Call the parent constructor:
        this._parent(x / 2);
    },
    f: function() {
        // Call the f() from "A":
        this._parent();

        // Do something specific to "B" here...
        this.x += 3;
    },
    g: function(a, b) {
        // Some code here...
    }
});

// The keyword "instanceof" works.

var X = Class({ /* ... */ });
var Y = X.extend({ /* ... */ });

var b = new B(11);
var x = new X();
var y = new Y();

a instanceof A; // true
b instanceof B; // true
b instanceof A; // true
x instanceof X; // true
y instanceof Y; // true
y instanceof X; // true

a instanceof B; // false
x instanceof Y; // false

x instanceof A; // false
b instanceof Y; // false

// If you have the urge to call an arbitrary parent's method
// from a child class, the way to do it (as of now) is the following:

var C = B.extend({
    init: function() { /* ... */ }
    x: function() {
        A.prototype.f.call(this);
    }
});

Useful JsDoc for your IDE

/** @class */
var A = Class(/** @lends A */ {
    /** @constructor */
    init: function() { /* ... */ }
    f: function() { /* ... */ }
});

/**
 * @class
 * @extends A
 */
var B = A.extend(/** @lends B */ {
    /** @constructor */
    init: function() { /* ... */ }
    g: function() { /* ... */ }
});

About

• Copyright 2012, Ivan Zhidkov.
• Released under the MIT License.
• Based on Simple JavaScript Inheritance and Simple Class Instantiation by John Resig (MIT Licensed).