1// fast apply, http://jsperf.lnkit.com/fast-apply/5
2module.exports = function (fn, args, that) {
3  var un = that === undefined;
4  switch (args.length) {
5    case 0: return un ? fn()
6                      : fn.call(that);
7    case 1: return un ? fn(args[0])
8                      : fn.call(that, args[0]);
9    case 2: return un ? fn(args[0], args[1])
10                      : fn.call(that, args[0], args[1]);
11    case 3: return un ? fn(args[0], args[1], args[2])
12                      : fn.call(that, args[0], args[1], args[2]);
13    case 4: return un ? fn(args[0], args[1], args[2], args[3])
14                      : fn.call(that, args[0], args[1], args[2], args[3]);
15  } return fn.apply(that, args);
16};
17