Shuffle an Array in JavaScript

The most common way to shuffle an array in JavaScript is by using the Fisher-Yates shuffle algorithm.

This algorithm efficiently shuffles an array in place. Here’s a straightforward way to implement this algorithm in JavaScript (I'll share an explanation after the code).

Also, while looking for the algorithm, I found this. It's a great visualization/explanation of the algorithm in action.

function shuffleArray(array) {
  for (let i = array.length - 1; i > 0; i--) {
    // Generate a random index lower than the current element index
    const j = Math.floor(Math.random() * (i + 1));

    // Swap elements i and j
    [array[i], array[j]] = [array[j], array[i]];
  }
  return array;
}

// Usage
const myArray = [1, 2, 3, 4, 5];
shuffleArray(myArray);
console.log(myArray); // Outputs random order like: [3, 5, 4, 1, 2]

How It Works

1. We loop over the array from the end of the array and decrement down to the second element.
2. Randomly select an index from 0 to the current index i.
3. Swap the element at the current index i with the element at the randomly selected index j.

When you run the function with an example array, it randomly shuffles the elements each time you execute it.