A simple JavaScript inheritance system

inheritance.js

/*
 * A simple JavaScript inheritance system
 * (Like Prototype's `Class.create()`, only without the crazy method wrapping and function decompilation)
 *
 * Usage
 * var A = Class.create({
 *     // `initialize` is the constructor
 *     initialize : function(x, y) {
 *         this.x = x;
 *         this.y = y;
 *     }
 *     toString : function() { return [x, y].join(' '); }
 * });
 *
 * // `B` is a child of `A`
 * var B = Class.create(A, {
 *     initialize : function(x, y, z) {
 *         // call this.<methodname>.$super to use the superclass implementation
 *         this.initialize.$super(x, y);
 *         this.z = z;
 *     },
 *     toString : function() { return [x, y, z].join(' '); }
 * });
 *
 * var a = new A(10, 10), b = new B(10, 10, 20);
 * a.toString() => '10 10'
 * b.toString() => '10 10 20'
 */
var Class = (function() {

	function create(baseclass, methods) {
		
		if (typeof methods == 'undefined') {
			methods = baseclass;
			baseclass = null;
		}
		
		methods.initialize = methods.initialize || function() { };
		
		var constructor = function() {
			var that = this;
			for (var k in methods) {
				(function (k) {
					methods[k].$super = function() {
						constructor.superclass[k].apply(that, arguments);
					}
				})(k);
			}
			methods.initialize.apply(this, arguments);
		}
		
		if (baseclass) {
			var subclass = function() { }
			subclass.prototype = baseclass.prototype;
			constructor.prototype = new subclass;
			constructor.superclass = baseclass.prototype;
		}
		constructor.prototype.constructor = constructor;
		
		for (var k in methods)
			constructor.prototype[k] = methods[k]
		
		return constructor;
	}

	return { create : create };
})();