UUID loses 2 bits of entropy

[dchest]

UUIDv4 includes 4 bits as version number and 2 or 3 bits as variant. This code:

export default function generate(): string {
  return "00000000-0000-4000-8000-000000000000".replace(
    /[0]/g,
    (): string =>
      // random integer from 0 to 15 as a hex digit.
      (crypto.getRandomValues(new Uint8Array(1))[0] % 16).toString(16)
  );
}

takes 4 bits for variant instead (8 is hard-coded), so it can generate only 2^120 uuids instead of 2^122.