random word, password generator

random_word.js

const randomWord = (len = 16, up = true, low = true, digits = true, special = '') => {
  const chars = [special];
  up &&  chars.push('ABCDEFGHIJKLMNOPQRSTUVWXYZ');
  low && chars.push('abcdefghijklmnopqrstuvwxyz');
  digits && chars.push('0123456789');
  const str = chars.join``;
  const word = [];
  for (let i = 0; i < len; ++i) {
    word[i] = str[Math.round(Math.random() * str.length) % str.length];
  }
  return word.join``;
};