sw.js

// pwa service worker
//STORAGE OF BROWSER
const CACHE_NAME = 'version-1';
const urlsToCache = ['index.html', 'offline.html'];
const self = this;

//installation
self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) => {
      console.log('Opened cache');

      return cache.addAll(urlsToCache);
    }),
  );
});

// listen for request
self.addEventListener('fetch', (event) => {
  event.respondWith(
    caches.match(event.request).then((res) => {
      return fetch(event.request).catch(() => caches.match('offline.html'));
    }),
  );
});

// actitivate the service worker
self.addEventListener('activate', (event) => {
  const cacheWhitelist = [];
  cacheWhitelist.push(CACHE_NAME);
  event.waitUntil(
    caches.keys().then((cacheNames) =>
      Promise.all(
        cacheNames.map((cacheName) => {
          if (!cacheWhitelist.includes(cacheName)) {
            return caches.delete(cacheName);
          }
        }),
      ),
    ),
  );
});