Server worker being registered twice

Question

I'm using FCM web notification service, when I am calling the register function:

if ('serviceWorker' in navigator) {
         window.addEventListener('load', function() {
        navigator.serviceWorker.register('/sw.js').then(function(registration) {
          // Registration was successful
          console.log('ServiceWorker registration successful with scope: ', registration.scope);
        }).catch(function(err) {
          // registration failed :(
          console.log('ServiceWorker registration failed: ', err);
        });
      });
    }

The service worker is registered twice, one because of this function, and one by the FCM script. This is my service worker code:

importScripts('https://www.gstatic.com/firebasejs/3.5.2/firebase-app.js');
importScripts('https://www.gstatic.com/firebasejs/3.5.2/firebase-messaging.js');

    'messagingSenderId': '<my senderid>'
});

const messaging = firebase.messaging();


messaging.setBackgroundMessageHandler(function (payload) {
   
    
    self.addEventListener('notificationclick', function (event) {
        event.notification.close();

        var promise = new Promise(function (resolve) {
            setTimeout(resolve, 1000);
        }).then(function () {
            return clients.openWindow(payload.data.locator);
        });

        event.waitUntil(promise);
    });
   
    var notificationTitle = payload.data.title;
    var notificationOptions = {
        body: payload.data.body,
        icon: payload.data.icon
    };
    return self.registration.showNotification(notificationTitle,
        notificationOptions);
});

One more thing, when I send test notifications, and I click the first message and it opens the URL correctly, but in the same instance of Chrome, all other messages I click open the URL of the first message. This problem does not happen on Firefox, just Chrome. I am using chrome version 55

Answer 1

With the firebase messaging SDK you don't need to call register.

If you call register, you can make the SDK use your service worker by calling useServiceWorker() (See: https://firebase.google.com/docs/reference/js/firebase.messaging.Messaging#useServiceWorker)

if ('serviceWorker' in navigator) {
  window.addEventListener('load', function() {
    navigator.serviceWorker.register('/sw.js')
    .then(function(registration) {
      messaging.useServiceWorker(registration);
    });
  });
}

The reason the SDK registers the service worker for you is that it sets a scope that will prevent it from interfering with any other service workers you might have.

Regarding your second issue, are you sending different URLs or are they the same URLs?