Get domain(site) from url using document.cookie hacking. without public suffix

get-domain.js

const isSite = (domain) => {
  console.log(domain)
  const key = "WILL_BE_FIRED." + 'xxxx-xxxx-xxx-xxxx'.replace(/[x]/g, (c) => {  
        const r = Math.floor(Math.random() * 16);  
        return r.toString(16);
  });
  document.cookie = `${key}=1; domain=${domain}; samesite`;
  // Test wrinting
  console.log("document.cookie", document.cookie)
  const canWrite = document.cookie.includes(`${key}=1`);
  console.log("canWrite", canWrite);
  // - [ ] More clear
  document.cookie = `${key}=; max-age=0`
  return canWrite;
};
const getSite = (urlString) => {
  const url = new URL(urlString);
  const parts = url.host.split(".").reverse();
  let testDomain = parts.shift(); // Why does "org" can write?
  for (const part of parts) {
    testDomain = testDomain ? part + "." + testDomain : part;
    if (isSite(testDomain)) {
      return testDomain
    }
  }
  throw new Error("No domain");
}
// Should call this in the site
const site = getSite(location.href);
console.log("site: ", site);
// https://azu.github.io/ → azu.github.io
// https://en.wikipedia.org → wikipedia.org