text: const CACHE_NAME = 'version 0.0.01';
  const cacheURL = [ 'index.html', 'offline.html'];
  
  const self = this;
  
  // Install ServiceWorker
  self.addEventListener('install', (event) => {
      event.waitUntil(
          caches.open(CACHE_NAME)
              .then((cache) => {
                  console.log('Opened cache');
                  return cache.addAll(cacheURL);
              })
      )
  })
  
  
  // Listen for requests
  self.addEventListener('fetch', (event) => {
      event.respondWith(
          caches.match(event.request)
              .then(() => {
                  return fetch(event.request)
                      .catch(() => (caches.match('offline.html')))
              })
      )
  })
  
  // Activate the ServiceWorker
  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);
                  }
              })
          ))
      )
  })