password.js

const lower = 'abcdefghijklmnopqrstuvwxyz';
const upper = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
const numbers = '0123456780';
const symbols = '!@#$%^&*_+-/~?'

/**
 * Generate a password from any number os groups of strings
 *
 * @example generatePassword([upper, symbols], 26)
 * 
 * @param {Array} options Array of strings to generate password from
 * @param {Number} length Length of desired password
 * 
 * @return {String}
 */
const generatePassword = (options = [], length=12) => {
  const str = [].concat(...options).join('');
  let password = '';
  for (let i = 0; i < length; i++) {
    password += str[Math.floor(Math.random() * str.length)]
  }
  return password;
}