How to randomize (shuffle) a JavaScript array?

ghz 1years ago ⋅ 9859 views

Question

I have an array like this:

var arr1 = ["a", "b", "c", "d"];

How can I randomize / shuffle it?

Answer

The de-facto unbiased shuffle algorithm is the Fisher-Yates (aka Knuth) Shuffle.

You can see a great visualization here (and the original post [linked to this](http://sedition.com/perl/javascript- fy.html))

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

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

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

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

  return array;
}

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

Some more info [about the algorithm](http://en.wikipedia.org/wiki/Fisher- Yates_shuffle) used.

#javascript