Notification https://developer.mozilla.org/ja/docs/Web/API/Notification/requestPermission

notification.js

Notification.requestPermission(function callback(res) {
  if (res === 'denied' || res === 'default') {
    console.error('ア');
    return;
  }
  window.setTimeout(function () {
    new Notification('title', {body: 'body'});
  }, 3000);
});