/*
Generates a UUID/GUID in Node.Js.
The script uses `Math.random` in combination with the timestamp for better randomness.
The function generate an RFC4122 (https://www.ietf.org/rfc/rfc4122.txt) version 4 UUID/GUID
*/

const Guid = () => {
  const pattern = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
  let currentDateMilliseconds = new Date().getTime()
  return pattern.replace(/[xy]/g, currentChar => {
    const randomChar = (currentDateMilliseconds + Math.random() * 16) % 16 | 0
    currentDateMilliseconds = Math.floor(currentDateMilliseconds / 16)
    return (currentChar === 'x' ? randomChar : (randomChar & 0x7 | 0x8)).toString(16)
  })
}

console.log(Guid()) // 'edc848db-3478-1760-8b55-7986003d895f'