Javascript Array where(predicate, context)

Array.prototype.where = Array.prototype.filter || function (predicate, context) {
 context = context || window;//from   w  w  w.  j av a2s  .  c o m
 var arr = [];
 var l = this.length;
 for (var i = 0; i < l; i++)
  if (predicate.call(context, this[i], i, this) === true) arr.push(this[i]);
 return arr;
};