Meet Web Push for Safari

// BrowserPetsWorker.js

function handleMessageEvent(event) {
    // ...
};
self.addEventListener('message', (event) => {
    handleMessageEvent(event);
});

function primeCaches() {
    // ...
};
self.addEventListener('install', (event) => {
    primeCaches();
});

self.addEventListener('fetch', (event) => {
    event.respondWith(caches.match(event.request));
});

// BrowserPetsMain.js

var registration;
if ('serviceWorker' in navigator) {
    let registration = await navigator.serviceWorker.getRegistration();
    if (!registration)
        registration = await navigator.serviceWorker.register('BrowserPetsWorker.js');
}

// BrowserPetsMain.js

async function subscribeToPush() {
    // ...
}

// BrowserPetsMain.html

<button onclick="subscribeToPush()">Register for Updates</button>

// BrowserPetsMain.js

async function subscribeToPush() {
    let serverPublicKey = VAPID_PUBLIC_KEY; 

    let subscriptionOptions = {
        userVisibleOnly: true,
        applicationServerKey: serverPublicKey
    };

    let subscription = await swRegistration.pushManager.subscribe(subscriptionOptions);

    sendSubcriptionToServer(subscription);
}

// BrowserPetsMain.js

async function subscribeToPush() {
    let serverPublicKey = VAPID_PUBLIC_KEY; 

    let subscriptionOptions = {
        userVisibleOnly: true,
        applicationServerKey: serverPublicKey
    };

    let subscription = await swRegistration.pushManager.subscribe(subscriptionOptions);

    sendSubcriptionToServer(subscription);
}

// BrowserPetsMain.js

async function subscribeToPush() {
    let serverPublicKey = VAPID_PUBLIC_KEY; 

    let subscriptionOptions = {
        userVisibleOnly: true,
        applicationServerKey: serverPublicKey
    };

    let subscription = await swRegistration.pushManager.subscribe(subscriptionOptions);

    sendSubcriptionToServer(subscription);
}

// BrowserPetsWorker.js

self.addEventListener('push', (event) => {
    let pushMessageJSON = event.data.json();

    // Our server puts everything needed to show the notification
    // in our JSON data.
    event.waitUntil(self.registration.showNotification(pushMessageJSON.title, {
        body: pushMessageJSON.body,
        tag: pushMessageJSON.tag,
        actions: [{
            action: pushMessageJSON.actionURL,
            title: pushMessageJSON.actionTitle,
        }]
    }));
}

// BrowserPetsWorker.js

self.addEventListener('notificationclick', async function(event) {
    if (!event.action)
        return;

    // This always opens a new browser tab,
    // even if the URL happens to already be open in a tab.
    clients.openWindow(event.action);
});