Javascript Array sort(fn)

Array.prototype.sort = function(fn) {
  if (!arguments[0]) {
    fn = function(a, b) {
      return a.compareTo(b);
    };//from   www .j  ava 2  s  . c  om
  }
  
  for (var i = 0, len = this.length; i < len - 1; i++) {
    for (var j = i + 1, len = this.length; j < len; j++) {
      if (fn(this[i], this[j]) > 0) {
        var tmp = this[i];
        this[i] = this[j];
        this[j] = tmp;
      }
    }
  }
  
  return this;
};