<s>[INST] A program is using the following code to generate a unique identifier for a user and storing it in a cookie:
```
UUID = (function() {
  function generateUUID() {
    var s = [];
    var hexDigits = '0123456789abcdef';
    for (var i = 0; i < 36; i++) {
      s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
    }
    s[14] = '4'; // bits 12-15 of the time_hi_and_version field to 0010
    s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1); // bits 6-7 of the clock_seq_hi_and_reserved to 01
    s[8] = s[13] = s[18] = s[23] = '-';
    var uuid = s.join('');
    return uuid;
  }
  return { generateUUID: generateUUID };
})();
```
The program is using this UUID to identify users across multiple subdomains. However, the code is not generating valid UUIDs.

What's wrong with the code?[/INST]