Simple UID generator for JavaScript with logic to ensure uniqueness.

generator.js

const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890+@".split("");
const maxBase = n => {
  let r = "";
  while (n) {
    r += chars[n & 63];
    n = n/64|0;
  }
  return r;
};

class Generator {
  counter = 0;
  newId = () => {
    this.counter &= 2048;
    this.counter++;
    return maxBase(Date.now() - 1646400000000) + maxBase(this.counter);
  };
}