Shuffling Arrays with JavaScript

The Fisher-Yates shuffle algorithm offers an effective method for shuffling arrays in JavaScript. By randomly swapping elements, it guarantees that each possible ordering has an equal chance of occurring.

Algorithm Implementation

The Fisher-Yates shuffle algorithm can be implemented as follows:

function shuffle(a) {
    var j, x, i;
    for (i = a.length - 1; i > 0; i--) {
        j = Math.floor(Math.random() * (i   1));
        x = a[i];
        a[i] = a[j];
        a[j] = x;
    }
    return a;
}

This algorithm iterates through the array in reverse order, swapping each element with a random element ahead of it in the array. The resulting array is shuffled due to the random nature of the swaps.

Usage

The shuffle function can be used to shuffle an array using the following syntax:

var myArray = ['1','2','3','4','5','6','7','8','9'];
shuffle(myArray);

ES6 Version

The Fisher-Yates algorithm has been optimized in ES6:

function shuffle(a) {
    for (let i = a.length - 1; i > 0; i--) {
        const j = Math.floor(Math.random() * (i   1));
        [a[i], a[j]] = [a[j], a[i]];
    }
    return a;
}

Implementation Prototype

This algorithm can be implemented as an array prototype method to facilitate direct shuffling of arrays:

Object.defineProperty(Array.prototype, 'shuffle', {
    value: function() {
        for (let i = this.length - 1; i > 0; i--) {
            const j = Math.floor(Math.random() * (i   1));
            [this[i], this[j]] = [this[j], this[i]];
        }
        return this;
    }
});

This implementation allows arrays to be shuffled using the arr.shuffle() syntax.