Short hash generator with collision checking

uid_generator.js

const letters = 'abcdefghijklmnopqrstuvwxyz';
const numbers = '1234567890';
const charset = letters + letters.toUpperCase() + numbers;

function pickRandomElement(array) {
  const { floor, random } = Math;
  return array[floor(random() * array.length)];
}

function randomString(length) {
  const { cache } = randomString;
  while (true) {
    let uid = '';
    for (let i = 0; i < length; i++) {
      uid += pickRandomElement(charset);
    }

    if (!cache.has(uid)) {
      cache.add(uid);

      return uid;
    }
  }
}

randomString.cache = new Set();