code: function getRandomArray (n) {
    var res = []
      , i, j, temp
      ;
  
    for (i = 0; i < n; i += 1) { res[i] = i; }
  
    for (i = n - 1; i >= 1; i -= 1) {
      j = Math.floor((i + 1) * Math.random());
      temp = res[i];
      res[i] = res[j];
      res[j] = temp;
    }
  
    return res;
  }
docs: Return an array with the numbers from 0 to n-1, in a random order
  Uses Fisher Yates algorithm
  Useful to get fair tests