simple wrapper for the ES5 Object.create mechanism and a function that fetches overridden methods from the prototype chain.

supr.js

/*
 * Copyright (C) 2011 Yehonatan Daniv <[email protected]>
 *
 *          DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
 * TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
 *
 * 0. You just DO WHAT THE FUCK YOU WANT TO.
 *
 * supr.js is a simple wrapper for the Object.create mechanism of ES5,
 * to ease the creation of objects via the Create function.
 * supr.js also provides the supr function that fetches overridden methods
 * from the prototype chain.
 *
 * example:
 *
 * var A = {
 *     name: 'Sam',
 *     who : function () {
 *         return this.name;
 *     }
 *  };
 *  var B = Create(A, {
 *      name: 'Bob',
 *      who : function () {
 *          return supr(this, 'who')() + ' is son of ' + this._parent_.name;
 *      }
 *  });
 *  var C = Create(B, {
 *      name: 'Alice'
 *  });
 *  console.log(B.who); // Bob is son of Sam
 *  console.log(C.who); // Alice is son of Bob
 */
(function (global, undefined) {
    /*
     * Some caching, and optionally, sandboxing
     */
    var Object = global.Object,
        getPrototypeOf = Object.getPrototypeOf,
        getOwnDesc = Object.getOwnPropertyDescriptor,
        objCreate = Object.create;
    /*
     * Define a sugary property for getting the prototype quickly
     * Notice it ain't enumerable
     */
    Object.defineProperty(Object.prototype, '_parent_', {
        get : function () {
            return getPrototypeOf(this);
        },
        set : function (obj) {} // if not defined causes errors in some places
    });
    /*
     * Simple recursion for retrieving a property's owner
     */
    function getPropertyOwner(obj, prop) {
        return obj.hasOwnProperty(prop) ? obj : getPropertyOwner(obj._parent_, prop);
    }
    /*
     * Gets an overridden method from down the prototype chain
     */
    function supr(object, key) {
        // if you named your function and not in strict mode you can drop the key argument
        var _key = key === undefined ? arguments.callee.caller.name : key,
            proto = object._parent_,
            prop = proto[_key];
        // make sure we got the actual super method and not the same one that went up the chain
        if ( ! object.hasOwnProperty(_key) ) // this won't happen if this method is defined in Object
            // find the last object that defined this property
            prop = getPropertyOwner(proto, _key)
            // get the super definition of this property
                   ._parent_[_key];
        // if it's a function then bind it to the right context
        return typeof prop === 'function' ? prop.bind(object) : prop;
    }
    /*
     * Helper function for turning simple objects into property descriptors
     */
    function _asDescriptor(obj) {
        var e, p, r = {};
        for ( p in obj )
            if ( e = getOwnDesc(obj, p) )
                r[p] = e;
        return r;
    }
    /*
     * A simple wrapper for Object.create
     */
    function Create(proto, self, as_generator) {
        var me = _asDescriptor(self),
            base = proto || {};
        return as_generator ? function () {
            return objCreate(base, me);
        } : objCreate(base, me);
    }
    global.Create = Create;
    global.supr = supr;
}(this));