How to randomize (shuffle) a JavaScript array?

Question

I have an array like this:

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

How can I randomize / shuffle it?

Answer 1

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

You can see a great visualization here.

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

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

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

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

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