Offline web push notifiion

Question

I’m creating a list to, and in it, I want to be able to create pre-programmed notifications. The application persists all data in Local Storage, IE, you do not have to use a push notification server

Then send messages to the Service Worker to manage notifications:

navigator.serviceWorker.register('./sw.js')
    .then(sw => {
        //Agenda uma futura notificação
        sw.active.postMessage({
            command: 'schedule',
            alert: { /* ... */ }
        });

        //Remove uma notificação agendada
        sw.active.postMessage({
            command: 'remove',
            alert: { /* ... */ }
        });
    })
    .catch(console.log);

And in Service Worker I use the setTimeout to schedule notifications

class Alert {
    /* ... */
}

const timer = {};

self.addEventListener('message', event => {
    switch (event.data.command) {
        case 'schedule':
            schedule(new Alert(event.data.alert));
            break;

        case 'remove':
            remove(event.data.alert.key);
            break;

        default:
            break;
    }
});

function remove(key) {
    if (timer[key]) {
        clearTimeout(timer[key]);

        delete timer[key];
    }
}

function schedule(alert) {
    if (!alert.canNotify()) {
        return;
    }

    remove(alert.key);

    timer[alert.key] = setTimeout(notify, alert.getTimeLeft(), alert.key, alert.title);
}

function notify(key, title) {
    self.registration.showNotification(title, {
        icon: '/assets/icons/android-chrome-192x192.png'
    });
}

It works, however, after notifying the user, I need to warn the application to update the information in Local Storage, since the Service Worker does not have access to it

I tried to send a message to clients in function notify:

self.clients.matchAll().then(
    clients => clients.forEach(
        client => {
            client.postMessage(key);
        }
    )
);

And in the application, update the data in the event message:

navigator.serviceWorker.addEventListener('message', event => {
    update(event.data);
});

But it only works if the application is open, which is a problem

How can I update this data?