Faster function binding than function.bind(...)

bind.js

var bind = function (callback, self) {
	if (arguments.length > 2) {
		var slice = Array.prototype.slice,
			push = Array.prototype.push,
			args = slice.call(arguments, 2);

		return function () {
			var full_args = slice.call(args);
			push.apply(full_args, arguments);

			return callback.apply(self, full_args);
		};
	}
	else {
		return function () {
			return callback.apply(self, arguments);
		};
	}
};