unique random id

generateUid.js

var generateUid = function() {
  var d = new Date().getTime();
  var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
    var r = (d + Math.random()*16)%16 | 0;
    d = Math.floor(d/16);
      return (c === 'x' ? r : (r&0x7|0x8)).toString(16);
    });
  return uuid;
};