How to randomize (shuffle) a javascript array?

The de-facto unbiased shuffle algorithm is the Fisher-Yates (aka Knuth) Shuffle.
See https://github.com/coolaj86/knuth-shuffle
You can see a great visualization here (and the original post linked to this)

function shuffle(array) {
  var currentIndex = array.length
    , temporaryValue
    , randomIndex
    ;

  // While there remain elements to shuffle...
  while (0 !== currentIndex) {

    // Pick a remaining element...
    randomIndex = Math.floor(Math.random() * currentIndex);
    currentIndex -= 1;

    // And swap it with the current element.
    temporaryValue = array[currentIndex];
    array[currentIndex] = array[randomIndex];
    array[randomIndex] = temporaryValue;
  }

  return array;
}

Used like so

var arr = [2, 11, 37, 42];
shuffle(arr);
console.log(arr);

Posted in: javascript