Generate random string/characters in JavaScript

randomString.js

/**
 * Generate random string
 * @param {number}  len       Length of string
 * @param {string}  charSet   Allowable characters
 * @return {string}
 */
function randomString(len = 10, charSet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789') {
  let randomString = '';
  for (let i = 0; i < len; i++) {
    let randomPoz = Math.floor(Math.random() * charSet.length);
    randomString += charSet.substring(randomPoz, randomPoz + 1);
  }
  return randomString;
}

module.exports = randomString;