Javascript Array qs()

// quick sort//ww w  . j  av a  2  s  .  c  om
Array.prototype.qs = function() {
 var len = this.length;
 if (len <= 1) {
  return this.slice(0);
 }
 var left = [];
 var right = [];
 var mid = [this[0]];
 for (var i = 1; i < len; i++) {
  if (this[i] < mid[0]) {
   left.push(this[i]);
  }
  else {
   right.push(this[i]);
  }
 }
 return left.qs().concat(mid.concat(right.qs()));
};

var arr = [3, 1, 5, 2, 4];
arr = arr.qs();