guid in javascript

uniqueId.js

uniqueId = function() {
    return 'xxxxxxxxxxxx4xxxyxxxxxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
      var r, v;
      r = Math.random() * 16 | 0;
      v = c === 'x' ? r : (r & 0x3 | 0x8);
      return v.toString(16);
    });
  };