Shuffle an array in place so that the positions of its values are random

shuffle.js

// shuffle.js © 2014 James Abney http://github.com/jabney
(function(ex) {
'use strict';

// Export shuffle to 'random' namespace.
var random = ex.random || (ex.random = Object.create(null));

// Shuffle an array in place so that the positions of its values are random.
random.shuffle = function shuffle(a) {
  var i, r, tmp, len = a.length;
  for (i = 0; i < len; i++) {
    r = i + Math.floor((len - i) * Math.random());
    tmp = a[i];
    a[i] = a[r];
    a[r] = tmp;
  }
  return a;
}

})(typeof exports !== 'undefined' && exports || this);