PYSA Website ciphered download links reversed

pysa_download_link_decipher.js

/*
 * PYSA Website ciphered download links reversed
 * http://pysa2bitc5ldeyfak4seeruqymqs4sj5wt5qkcq7aoyg4h2acqieywad.onion
 */
function addClass(className, element) {
  elements = querySelectorAll(className);
  console.log(elements);
  for (var seed = 0; seed < elements['length']; seed++) {
    elements[seed]['classList']['add'](element)
  }
}

function removeClass(className, element) {
  elements = querySelectorAll(className);
  console.log(elements);
  for (var seed = 0; seed < elements['length']; seed++) {
    elements[seed]['classList']['remove'](element)
  }
}
var clickMeAll = querySelectorAll('.showFiles');
document.addEventListener('click', function (element) {
  if (!element.target['matches']('.showFiles')) {
    return
  };
  element.preventDefault();
  addClass('.files', 'hidden');
  removeClass('.files', 'show');
  let id = element.target['getAttribute']('data-num');
  let dstElement = document['querySelector']('#files-' + id);
  dstElement['classList']['add']('show');
  dstElement['classList']['remove']('hidden')
}, false);
document.addEventListener('submit', function (element) {
  element.preventDefault();
  let finalElement = element.target;
  let key = finalElement['querySelector']('input[name=shellcode]')['value'];
  let fileSize = finalElement['querySelector']('input[name=size]')['value'];
  let babyShitHaha = finalElement['querySelector']('input[name=phrase]')['value'];
  let decipheredLink = decrypt(key, babyShitHaha);
  finalElement['innerHTML'] = '<a href="' + decipheredLink + '">Download (' + fileSize + ')</a>'
}, false);
const giveUniqueKey = (seeds) => {
  let ret = 0,
    swapSwitch = true;
  for (let seed of seeds) {
    if (swapSwitch) {
      ret += seed['charCodeAt']()
    } else {
      ret -= seed['charCodeAt']()
    };
    swapSwitch = !swapSwitch
  };
  if (ret < 0) {
    ret = ret * (-1)
  };
  ret += seeds['length'];
  return ret % 256
};
const decrypt = (cipher, seeds) => {
  let shittyKey = giveUniqueKey(seeds);
  cipher = atob(cipher);
  let ret = `${''}`;
  cipher.split(' ').forEach((element) => {
    if (element.charCodeAt() < shittyKey) {
      ret += String.charCodeAt((element.charCodeAt() - shittyKey + 256) % 256)
    } else {
      ret += String.charCodeAt((element.charCodeAt() - shittyKey) % 256)
    }
  });
  return ret
}