makeUpgradeCode.js

// produces unique enough base36 serial based on nanosecond time
function makeUpgradeCode() {
  const [nanoseconds, seconds] = process.hrtime();
  const time = (seconds * 1e6 + nanoseconds)
    .toString(26)
    .split('')
    .map(x => (parseInt(x, 26) + 10).toString(36))
    .concat(Math.random().toString(10).substring(2).split(''))
    .slice(0, 12);
  const [a, b, c, d, e, f, g, h, i, j, k, l] = time;

  return `${l}${h}${d}-${i}${e}${a}-${f}${b}${j}-${c}${k}${g}`;
}

// const codes = {};
// for (let x = 0; x < 100000; x++) {
//   const code = makeUpgradeCode();
//   if (codes[code]) {
//     console.log(code);
//   }
//   codes[code] = true;
// }