Subscription steps

subscribe.js

async function subscribe(syncToken = false) {
    try {
        // STEP 1: Load and init firebase SDK
        await loadAndInitFirebase('firebase');
        const messaging = firebase.messaging();

        // STEP 2: Use registered Service Worker
        const swReg = await getServiceWorkerRegistration();
        messaging.useServiceWorker(swReg);

        // STEP 3: Request user permission
        // If called only for syncing token, the user has already granted permission
        if (!syncToken) {
            await requestPermission(messaging);
        }

        // STEP 4: Retrieve token and sync it with server
        const token = await getToken(messaging);
        await sendTokenToServer(token);

        // STEP 5: Finally emit success event
        emitEvent('subscribe-success');
    } catch (ex) {
        // All errors have been handled by individual functions
    }
}