sw.js

const staticCacheName = 'aws-amplify-docs-v1';
const filesToCache = [
  '/',
  'images/',
  'theme/assets/css/style.css',
  'theme/assets/js/'
];

self.addEventListener('install', event => {
    console.log('Attempting to install service worker and cache static assets');
    event.waitUntil(
      caches.open(staticCacheName)
      .then(cache => {
        return cache.addAll(filesToCache);
      })
    );
});

self.addEventListener('fetch', event => {
    //console.log('Fetch event for ', event.request.url);
    event.respondWith(
      caches.match(event.request)
      .then(response => {
        if (response) {
          //console.log('Found ', event.request.url, ' in cache');
          return response;
        }
        //console.log('Network request for ', event.request.url);
        return fetch(event.request)
        .then(response => {
            // TODO 5 - Respond with custom 404 page
            return caches.open(staticCacheName).then(cache => {
              cache.put(event.request.url, response.clone());
              return response;
            });
          });
  
      }).catch(error => {
  
        // TODO Respond with custom offline page
  
      })
    );
});

self.addEventListener('activate', event => {
    //console.log('Activating new service worker...');
    const cacheWhitelist = [staticCacheName];
    event.waitUntil(
      caches.keys().then(cacheNames => {
        return Promise.all(
          cacheNames.map(cacheName => {
            if (cacheWhitelist.indexOf(cacheName) === -1) {
              return caches.delete(cacheName);
            }
          })
        );
      })
    );
});