Fisher-Yates JS implementation

gistfile1.js

function shuffle(array) {
  var unshuffled = array.length,
      copy,
      remaining;

  // While there are unshuffled elements
  while (unshuffled) {
    // Get one that hasn't been replaced yet
    remaining = Math.floor(Math.random() * unshuffled--);
    // And replace it with the unshuffled element
    copy = array[unshuffled];
    array[unshuffled] = array[remaining];
    array[remaining] = copy;
  }

  return array;
}