from: http://stackoverflow.com/questions/105034/create-guid-uuid-in-javascript

guid.js

'use strict';
function guid() {

  function s4() {
    return Math.floor((1 + Math.random()) * 0x10000)
      .toString(16)
      .substring(1);
  }

  return s4() + s4() + '-' + s4() + '-' + s4() + '-' + s4() +
    '-' + s4() + s4() + s4();
}