javascriptarraysrandomshuffle

How to randomize (shuffle) a JavaScript array?


I have an array like this:

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

How can I randomize / shuffle it?


Solution

  • 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)

    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 used.