firebase-messaging-sw.js

// This service worker will allow browser to receive a notification while app is running in the background/closed.
importScripts("https://www.gstatic.com/firebasejs/8.10.1/firebase-app.js");
importScripts("https://www.gstatic.com/firebasejs/8.10.1/firebase-messaging.js");
importScripts("js/keys.js");
// Initialize Firebase
firebase.initializeApp(firebaseConfig);
const messaging = firebase.messaging();
messaging.setBackgroundMessageHandler(function (payload) {
    const promiseChain = clients
        .matchAll({
            type: "window",
            includeUncontrolled: true
        })
        .then(windowClients => {
            for (let i = 0; i < windowClients.length; i++) {
                const windowClient = windowClients[i];
                windowClient.postMessage(payload);
            }
        })
        .then(() => {
            return registration.showNotification("New Message");
        });
    return promiseChain;
});
self.addEventListener('notificationclick', function (event) {
    console.log('notification received: ', event)
});