A example of register file for a service worker #ServiceWorker

main.js

/*
//  1. verifico que el navegador soporte serviceWorker  
//  2. registro el service worker
//  3. genero la subscripcion (
//      - pido permiso al cliente 
//      - genero datos de subscription 
//      - verifico que no haya otra subcripcion anterior
//      - si no hay subscription guardo sino retorno la existente
//  )
*/

const PUBLIC_VAPID_KEY = '';

const register = async () => {
    if ('serviceWorker' in navigator) {
        const swRegistration = await registerServiceWorker();
        await generateSubscription(swRegistration);
    } else throw new Error('ServiceWorkers are not supported by your browser!');
}

const registerServiceWorker = async () => {
    return await await navigator.serviceWorker.register('/sw.js', {
        scope: '/'
    });
}

const generateSubscription = async swRegistration => {
    await window.Notification.requestPermission();
    const pushSubscription = await swRegistration.pushManager.getSubscription();

    if (!pushSubscription) {

        const subscription = await swRegistration.pushManager.subscribe({
            userVisibleOnly: true,
            applicationServerKey: urlBase64ToUint8Array(PUBLIC_VAPID_KEY) 
        });

        const saved = await saveSubscription(subscription);
        if (saved) return saved;
		throw Error('Subscription not saved!');
    } else return pushSubscription;

}

const saveSubscription = async subscription => {
    const response = await fetch('/notification/subscription/comensal', {
        method: 'POST',
        body: JSON.stringify({
            other: document.getElementById("other").value,
            subscription: subscription
        }),
        headers: {
            "Content-Type": "application/json",
            //"X-CSRF-TOKEN": $('meta[name="csrf-token"]').attr('content')
        }
    });
  
	return response.status === 200 ? response.json() : false;
}

function urlBase64ToUint8Array(base64String) {
    const padding = '='.repeat((4 - (base64String.length % 4)) % 4);
    const base64 = (base64String + padding).replace(/\-/g, '+').replace(/_/g, '/');

    const rawData = window.atob(base64);
    const outputArray = new Uint8Array(rawData.length);

    for (let i = 0; i < rawData.length; ++i) {
      outputArray[i] = rawData.charCodeAt(i);
    }

    return outputArray;
}

register();