Class

class.js

function Class(sup, pro) {
	if (sup && typeof sup === 'object')
		pro = sup, sup = Object;

	var con = Object.getOwnPropertyDescriptor(pro, 'constructor');
	if (!con)
		con = {value: Function(), writable: true, configurable: true};

	if (con.configurable) {
		con.enumerable = false;
		Object.defineProperty(pro, 'constructor', con);
	}

	con = pro.constructor;
	con.prototype = pro;
	con.superclass = sup;
	con.__proto__ = Class.prototype;
	pro.__proto__ = sup && sup.prototype;

	return Proxy.createFunction(con, function() con.createInstance(arguments));
}
Class = Class(Function, {
	constructor: Class,
	$super: function $super() {
		var sup = this.superclass;
		var method = sup.prototype[$super.caller === this ? 'constructor' : $super.caller.name];
		return Function.prototype.call.apply(method, arguments);
	},
	isSubClass: function isSubClass(cls) {
		return this.prototype instanceof cls;
	},
	createInstance: function createInstance(args) {
		var instance = Object.create(this.prototype);
		var result = this.apply(instance, args || []);
		return result instanceof Object ? result : instance;
	},
	toString: function toString() {
		var arr = [];
		var cls = this;
		do {
			arr.push(cls.name);
		} while (cls = cls.superclass);
		return '[object Class [class ' + arr.join(', ') + ']]';
	},

	getOwnPropertyDescriptor: function(name) Object.getOwnPropertyDescriptor(this, name),
	getPropertyDescriptor: function(name) Object.getPropertyDescriptor(this, name),
	getOwnPropertyNames: function(name) Object.getOwnPropertyNames(this, name),
	getPropertyNames: function(name) Object.getPropertyNames(this, name),
	defineProperty: function(name) Object.defineProperty(this, name),
	delete: function(name) delete this[name],
	fix: function() {
		if (!Object.isFrozen(this))
			return void 0;

		var res = {};
		Object.getOwnPropertyNames(this).forEach(function(name) {
			res[name] = Object.getOwnPropertyDescriptor(this, name);
		}, this);
		return res;
	},
	has: function(name) name in this,
	hasOwn: function(name) Object.prototype.hasOwnProperty.call(this, name),
	get: function(receiver, name) {
		if (name in this)
			return this[name];

		var method = this.prototype[name];
		if (typeof method === 'function')
			return Function.prototype.call.bind(method);

		return void 0;
	},
	set: function(receiver, name, val) this[name] = val,
	enumerate: function() [name for (name in this)],
	keys: function() Object.keys(this),
});

Yikes. Where does this actually work?
Gecko only I would guess.

Here is my Greasemonkey script using this code.
http://userscripts.org/scripts/show/67840