Unrandom — for when someone says they want a random selection, but what they mean is uniformly sampled without repetition.

Unrandom.js

// Usage: 
// var randomiser = new Unrandom(["alpha", "bravo", "charlie", "delta"]);
// console.debug(randomiser.get());

var Unrandom = function(_items) {

  var items,
      last_item,
      marker = 0;

  var init = function() {
    items = _items;
    shuffle();
  };

  var get = function() {
    var new_item = last_item;
    while (new_item == last_item) {
      marker += 1;
      if (marker == items.length) {
        shuffle();
        marker = 0;
      }
      new_item = items[marker];
    }
    last_item = new_item;

    return new_item;
  };

  var shuffle = function() {
    var l = items.length, t, r;
    if (l == 0) return;

    while (--l) {
      r = Math.floor(Math.random() * l + 1);
      t = items[l];
      items[l] = items[r];
      items[r] = t;
    }
  }

  init();

  return {
    get: get
  };
};