This snippet here uses Fisher-Yates Shuffling Algorithm (https://www.wikiwand.com/en/Fisher–Yates_shuffle) to shuffle a given array.

array_shuffle.js

/**
 * Example:
 * var a = [ 1, 2, 3, 4, 5, 6, 7, 8 ];
 * var b = shuffleArray( a );
 * console.log(b);
 * // [2, 7, 8, 6, 5, 3, 1, 4]
 */

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