Create unique id in js

uuid.js

// http://stackoverflow.com/a/2117523/1983554
function createId() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
    .replace(/[xy]/g, function(c) {
      var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
      return v.toString(16);
  });
}