sw.js

var CACHE_NAME = 'my-offline-cache';
var FILES_TO_CACHE = [
  './index.html',
  './assets/images/1.jpg',
  './assets/images/2.jpg',
  './assets/images/3.jpg',
  './assets/images/verified-css3.gif',
  './assets/images/icons/icon-256.ico',
  './assets/scripts/script.js',
  './assets/styles/style.css',
  './assets/styles/fonts/NotoSans/NotoSans-Regular.woff2'
];

//Please work
self.addEventListener('install', (evt) => {
  console.log('[ServiceWorker] Install');
  evt.waitUntil(
      caches.open(CACHE_NAME).then((cache) => {
        console.log('[ServiceWorker] Pre-caching offline page');
        return cache.addAll(FILES_TO_CACHE);
      })
  );
  self.skipWaiting();
});

self.addEventListener('activate', (evt) => {
  console.log('[ServiceWorker] Activate');
  evt.waitUntil(
      caches.keys().then((keyList) => {
        return Promise.all(keyList.map((key) => {
          if (key !== CACHE_NAME) {
            console.log('[ServiceWorker] Removing old cache', key);
            return caches.delete(key);
          }
        }));
      })
  );
  self.clients.claim();
});

self.addEventListener('fetch', (evt) => {
  console.log('[ServiceWorker] Fetch', evt.request.url);
  if (evt.request.mode !== 'navigate') {
    // Not a page navigation, bail.
    return;
  }
  evt.respondWith(
      fetch(evt.request)
          .catch(() => {
            return caches.open(CACHE_NAME)
                .then((cache) => {
                  return cache.match('./index.html');
                });
          })
  );
});