Two ways of shuffling arrays in javascript

shuffleArray.js

// a simple and efficient way to shuffle
// a relatively small array. Doesn't work well
// with a lot of indices. See: http://stackoverflow.com/a/18650169/2104866

var numbers = [1,2,3,4,5,6];

numbers.sort(function() {
  return .5 - Math.random();
});


// much more clever way to randomize an array
// using Fisher-Yates shuffle algorithm.

Array.prototype.shuffle = function() {
  var i = this.length, j, temp;
  if ( i == 0 ) return this;
  while ( --i ) {
     j = Math.floor( Math.random() * ( i + 1 ) );
     temp = this[i];
     this[i] = this[j];
     this[j] = temp;
  }
  return this;
}



// if, for some reason, you can't use prototype,
// here's the same Fisher-Yates algorithm as a function

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;
    }
    return array;
}