text: // Give the service worker access to Firebase Messaging.
  // Note that you can only use Firebase Messaging here, other Firebase libraries
  // are not available in the service worker.
  importScripts('https://www.gstatic.com/firebasejs/6.3.4/firebase-app.js');
  importScripts('https://www.gstatic.com/firebasejs/6.3.4/firebase-messaging.js');
  importScripts('libs/fbconfig.js');
  // Initialize the Firebase app in the service worker by passing in the
  // messagingSenderId.
  firebase.initializeApp(config);
  
  const messaging = firebase.messaging();
  
  