function uuid(): string {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, c => {
    const r = (Math.random() * 16) | 0;
    const v = c == 'x' ? r : (r & 0x3) | 0x8;
    return v.toString(16);
  });
}
Based on the rfc4122-compliant solution posted at
http://stackoverflow.com/questions/105034