Fisher-Yates or Knuth Shuffle

shuffle.js

var swap = function (list, i, j) {
  // swap items at i-th and j-th entries of list
  // console.log(swap(items, 0, 2)); == [3, 2, 1, 4, 5]
  var tmp = list[i];
  list[i] = list[j];
  list[j] = tmp;
  return list;
};

var randomInt = function(max) {
  // Return a random integer between zero and max
  return Math.floor(Math.random() * max);
};

var shuffle = function (items) {
  var length = items.length;
  var i = items.length;

  while (--i) {
    // Swap last unshuffled element at index i
    // with a random element from the unshuffled section (up to i-1)
    swap(items, i, randomInt(i-1));
  }
  return items;
};

var items = [1, 2, 3, 4, 5];

for (var i = 0; i < 10; i++) {
  console.log(shuffle(items));
}