Javascript Array isEqual(target)

"use strict";// ww  w  .ja  v a2 s  .com
Array.prototype.isEqual = function(target){
  if (this == target) return true;
  if (this == null || target == null) return false;
  if (this.length != target.length) return false;
  for(var i in this){
    if (
      (this[i] !== target[i]) &&
      (typeof this[i].isEqual != "function" ||
      !this[i].isEqual(target[i]))
    ){
      return false;
    }
  }
  return true;
}