fcm-tpl.html

<script src="https://www.gstatic.com/firebasejs/5.11.1/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/5.11.1/firebase-messaging.js"></script>
<script>
  // Your web app's Firebase configuration
  var firebaseConfig = {{firebaseConfig}};
  // Initialize Firebase
  firebase.initializeApp(firebaseConfig);

  // Prepare to receive messages
  const messaging = firebase.messaging();
  messaging.usePublicVapidKey("{{fcmPublicVapidKey}}");
  messaging.requestPermission().then(function() {
    console.log('Notification permission granted.');
    // TODO(developer): Retrieve an Instance ID token for use with FCM.
    // ...
    messaging.getToken().then(function(token) {
      if (token) {
        console.log('Token got', token);
        sendToServer(token);
      } else {
        console.log('No Instance ID token available. Request permission to generate one.');
      }
    }).catch(function(err) {
      console.log('An error occurred while retrieving token. ', err);
    });

    messaging.onMessage(function (payload) {
      // no time to complete this function
      console.log(payload);
    });

  }).catch(function(err) {
    console.log('Unable to get permission to notify.', err);
  });

  messaging.onTokenRefresh(function() {
    messaging.getToken().then((token) => {
      sendToServer(token);
    });
  });

  function sendToServer(token) {
    window.fetch(SERVER_ADDRESS + '/addToken?token=' + token, {
      credentials: 'include'
    });
  };
</script>