Javascript Array aggregate(func, seed)

Array.prototype.aggregate = Array.prototype.reduce || function (func, seed) {
  var arr = this.slice(0);
  var l = this.length;
  if (seed == null) seed = arr.shift();

  for (var i = 0; i < l; i++)
    seed = func(seed, arr[i], i, this);//from   w  w  w . ja v a  2s  .  com

  return seed;
};