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Randomize an Array in JavaScript

Last Updated on Wednesday 5th Oct 2022

shuffle array javascript

javascript array shuffle

Shuffle an Array Using Fisher-Yates Shuffle Algorithm

js shuffle array

  • The Fisher-Yates shuffle is a highly efficient and completely unbiased way to randomize the elements in an array.
  • It's a fairly simple method.
  • Start at the end of the list, and swap the last element with a random element from earlier in the list.
  • Go down one and repeat, until you're at the beginning of the list, with all of the shuffled elements at the end of the list.
			
					function shuffle(arr) {
    const len = arr.length;
    const shuffled = new Array(len);

    let i = 0;
    let ran;
    const end = len - 1;

    while (i <= end) {
        ran = ~~(Math.random() * (i + 1));

        if (ran !== i) {
            shuffled[i] = shuffled[ran];
        }

        shuffled[ran] = arr[i];

        i++;
    }

    return shuffled;
}

console.log(shuffle([1, 2, 3, 4]));

javascript randomize array

You can do it easily with map and sort. Put Each element in the array in an object, and give it a random sort key and sort using that key, then map back to the original objects.

			
					let arr = ['a','b','q', 1, 2, 3 ];

let newArr = arr
  .map((value) => ({ value, sort: Math.random() }))
  .sort((a, b) => a.sort - b.sort)
  .map(({ value }) => value);

console.log(newArr);

javascript randomize array

ES6 Pure using array.reduce

			
					function getShuffledArr (arr){
    return arr.reduce( 
        (newArr, _, i) => {
            var rand = i + ( Math.floor( Math.random() * (newArr.length - i) ) );
            [newArr[rand], newArr[i]] = [newArr[i], newArr[rand]]
            return newArr
        }, [...arr]
    )
}

javascript shuffle array

Random Array in Javascript

			
					function randomizeArray(arr) {
  var curArr = [],
    start;

  for (var i = arr.length; i >= arr.length && i > 0; i--) {
    start = Math.floor(Math.random() * arr.length);
    curArr.push(arr.splice(start, 1)[0]);
  }

  return curArr;
}

			
	

			
	
	


			
					randomizeArray([2, 4, 5, 6, 8, 9]);

// [8, 2, 4, 5, 6, 9]

randomizeArray([28, 25, 77, 66, 88, 99]);

// [ 77 , 99, 66, 28, 88, 25 ]