function randomMixingArray(arr) {
  var randomIndex;
  var randomEl;

  for (var i = arr.length - 1; i > 0; i--) {
    randomIndex = Math.floor(Math.random() * (i + 1));
    randomEl = arr[randomIndex];
    arr[randomIndex] = arr[i];
    arr[i] = randomEl;
  }

  return arr;
}