・・・・。version 1 と 4でさえも・・・

var create_RFC4122_UUID_Generator_version_4 = function (MS_GUID/*Boolean*/) {
  var int     = Math.floor;
  var random  = Math.random;
  var version = 4;

  var randD4Hex= function () {
    return ('000' + int (random () * (1 << 16)).toString (16)).slice (-4);
  };

  return function () {
    return [
      randD4Hex () + randD4Hex (),// low
      randD4Hex (),// mid
      (int ((version << 12) | random () * (1 << 12))).toString (16),  // high
      (MS_GUID
       ? (5 << 13) | (random () * (1 << 13))
       : (4 << 13) | (random () * (1 << 14))
      ).toString (16), //clock_seq
      randD4Hex () + randD4Hex () + randD4Hex () //node
    ].join ('-');
  };
};

こっそり、ごっそり。