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Randomize a List in Javascript


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);

Output

[ 2, 37, 42, 11 ]

Example 2


It picks a random element for each original array element, and excludes it from the next draw, like picking randomly from a deck of cards.

This clever exclusion swaps the picked element with the current one, then picks the next random element from the remainder, looping backwards for optimal efficiency, ensuring the random pick is simplified (it can always start at 0), and thereby skipping the final element.

function shuffleArray(array) {
    for (var i = array.length - 1; i > 0; i--) {
        var j = Math.floor(Math.random() * (i + 1));
        var temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
}


Conclusion

In this page (written and validated by ) you learned about . What's Next? If you are interested in completing Javascript tutorial, we encourage you simply to start here: Javascript Tutorial.



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