Generate a valid UUID v4 using nodejs' CSPRNG

uuid4.js

return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
  .replace(
    /[xy]/g,
    char => {
      const rnd = parseInt(
        require('crypto')
          .randomBytes(1) // get one byte
          .toString('hex')// encode it to hex
          .slice(0, 1),   // slice to one char
        16
      ); //parse int (ranges from 0-15)
      // mask y value and return as hex
      return ((char == 'x') ? rnd : (rnd & 0x3 | 0x8)).toString(16);
    }
  );