Array shuffle, without creating new array

gistfile1.txt

var array = [1, 2, 3, 4, 5, 6];

Array.prototype.shuffle = function() {
  var i = this.length,
      tmp,
      randIndex;
  while (--i) {
    randIndex = Math.floor(i * Math.random());
    tmp = this[i];
    this[i] = this[randIndex];
    this[randIndex] = tmp;
    // or you can swap variables
    // this[i] = [this[randIndex], this[randIndex] = this[i]][0]
  }
    
  return this;
}

array.shuffle();