Bind that can be override with other arguments; can be used with call and apply too (mixcall & mixapply)

New_Bind.js

// New methods for all functions: mixapply, mixcall, and mixbind
// Allows you to force arguments and context even after using .bind
// To skip any argument you can use NULL
// License: Public Domain
(function () {

	var __bind = Function.prototype.bind;
	var toArray = function (a) {
		return Array.prototype.slice.call(a);
	};

	Function.prototype.bind = function () {
		var args = toArray(arguments);
		var f = __bind.apply(this, args);
		f.mixcall = mix.apply(this, args.concat(['mixcall']));
		f.mixapply = mix.apply(this, args.concat(['mixapply']));
		f.mixbind = mix.apply(this, args.concat(['mixbind']));
		return f;
	};

	var mix = function (c) {
		var oldArgs = toArray(arguments);
		var org = this;
		var op = oldArgs.pop();
		return function () {
			var args = toArray(arguments);
			if (op === "mixapply") {
				args = args[1];
				args.unshift(arguments[0]);
			}
			var max = Math.max(args.length, oldArgs.length);
			while (max--) args[max] = args[max] == null ? oldArgs[max] : args[max];
			if (op === "mixbind") {
				return org.bind.apply(org, args);
			}
			return org.apply(args[0], args.slice(1));
		};
	};

	Function.prototype.mixcall = function () {
		return mix.apply(this, toArray(arguments).concat(["mixcall"]))();
	};

	Function.prototype.mixapply = function () {
		return mix.apply(this, toArray(arguments).concat(["mixapply"]))();
	};

	Function.prototype.mixbind = function () {
		return mix.apply(this, toArray(arguments).concat(["mixbind"]))();
	};

})();

E.g:

var foo = function(a){ return a * this; };
var bar = foo.bind(10, 500);
console.log( bar.mixcall(null, 2) ); // Return 20