Extract bind, call and apply to use as standalone functions, instead of as methods of other functions.

callfn.js

var bind = Function.prototype.bind ? Function.prototype.bind.bind(Function.prototype.call) : (function(){
	/**
	 * Some browsers don't have the bind function, so you can use the code 
	 * 	below to achieve more or less the same results... A more complete 
	 * 	implementation of binder can be found on mdn, this was just a quick hack.
	 */
	function binder(fn, that){
		for(var i = 0, iLen = arguments.length, arr = new Array(iLen); i < iLen; i++){
			arr[i] = arguments[i];
		}

		arr.splice(0, 2);

		return function(){
			for(var j = 0, jLen = arguments.length, arr2 = new Array(jLen); j < jLen; j++){
				arr2[j] = arguments[j];
			}

			[].unshift.apply(arr2, arr);

			return fn.apply(that, arr2);
		};
	}

	return binder(Function.prototype.call, binder, Function.prototype.call);
}());

var call = bind(Function.prototype.call);
var apply = bind(Function.prototype.apply);

var test = function(a){ console.log('hey', this, a); };
bind(test, {a:1}, 1)()
call(test, {a:1}, 1)
apply(test, {a:1}, [1])