Simple JavaScript Inheritance

core.js

    /**
     * Simple JavaScript Inheritance
     * @see http://ejohn.org/blog/simple-javascript-inheritance/
     *
     * By John Resig http://ejohn.org/
     * MIT Licensed.
     */
    var initializing = false,
        fnTest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /.*/;

    // The base Class implementation (does nothing)
    root.Class = function() {};

    // Create a new Class that inherits from this class
    Class.extend = function(prop) {
        var _super = this.prototype;

        // Instantiate a base class (but only create the instance,
        // don't run the init constructor)
        initializing = true;
        var prototype = new this();
        initializing = false;

        // Copy the properties over onto the new prototype
        for (var name in prop) {
            // Check if we're overwriting an existing function
            prototype[name] = typeof prop[name] === 'function' &&
                typeof _super[name] === 'function' && fnTest.test(prop[name])
                ? (function(name, fn){
                    return function(){
                        var tmp = this._super;

                        // Add a new ._super() method that is the same method
                        // but on the super-class
                        this._super = _super[name];

                        // The method only need to be bound temporarily, so we
                        // remove it when we're done executing
                        var ret = fn.apply(this, arguments);
                        this._super = tmp;

                        return ret;
                    };
                })(name, prop[name])
                : prop[name];
        }

        // The dummy class constructor
        function Class() {
            // All construction is actually done in the init method
            if (!initializing && this.init) {
                this.init.apply(this, arguments);
            }
        }

        // Populate our constructed prototype object
        Class.prototype = prototype;

        // Enforce the constructor to be what we expect
        Class.prototype.constructor = Class;

        // And make this class extendable
        Class.extend = arguments.callee;

        return Class;
    };