adblocker.js

async function checkForAdBlocker() {
  let Blocked;

  async function Request() {
    try {
      return fetch(
        new Request(
"https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js", {
          method: 'HEAD',
          mode: 'no-cors'
        }))
        .then(function(response) {
          // There is no AdBlocker
          Blocked = false;
          return Blocked;
        }).catch(function(e) {
          // Failed, Because of an AdBlocker
          Blocked = true;
          return Blocked;
        });
    } catch (error) {
      console.log(error);
      Blocked = true;
      return Blocked;
    }
  }

  return Blocked !== undefined ? Blocked : await Request();
}

const usingBlocker = await checkForAdBlocker();