setPrototypeOf

gistfile1.js

/*
Object.setPrototypeOf is not going to happen. Writable __proto__ 
is a giant pain to implement (must serialize to cycle-check) 
and it creates all sorts of type-confusion hazards (Brendan Eich).
*/

Object.setPrototypeOf = function (object, proto) {
    var __proto__ = proto;
    
    do {
        if (object === __proto__)
            throw new Error('Circular prototype chain');
    }
    while (__proto__ = Object.getPrototypeOf(__proto__));
    
    object.__proto__ = proto;
    return object; 
};