Basic service worker configuration

sw.js

const CACHE_NAME = 'whatsappweb-cache-v9';
const { assets } = global.serviceWorkerOption;

const urlsToCache = ['./', './index.html', ...assets];

self.addEventListener('install', event => {
  console.log('Service Woker Started');
  event.waitUntil(
    caches.open(CACHE_NAME).then(cache => {
      console.log('Opened cache');
      return cache.addAll(urlsToCache);
    })
  );
});

self.addEventListener('activate', event => {
  console.log('Service Woker Activated');
  event.waitUntil(
    caches.keys().then(cacheNames =>
      Promise.all(
        cacheNames.map(thisCachenName => {
          if (thisCachenName !== CACHE_NAME) {
            return caches.delete(thisCachenName);
          }
          return caches;
        })
      )
    )
  );
});

self.addEventListener('fetch', e => {
  e.respondWith(
    caches
      .match(e.request)
      .then(response => {
        if (response) {
          return response;
        }
        const requestClone = e.request.clone();
        fetch(requestClone).then(response => {
          if (!response) {
            return response;
          }
          const responseClone = response.clone();
          caches.open(CACHE_NAME).then(cache => {
            cache.put(e.request, responseClone);
            return response;
          });
        });
      })
      .catch(err => console.log('error while Service Woeker', err))
  );
});