sw.js

const staticCacheName = 'site-static-v1';
const assets = [
  
  '/',
  '/index.html',
  '/assets/js/ui.js',
  '/assets/css/main.css',
  '/assets/images/background-home.jpg',
  'https://fonts.googleapis.com/css?family=Lato:300,400,700',
];
self.addEventListener('install', evt => {
  evt.waitUntil(
    caches.open(staticCacheName).then((cache) => {
      console.log('caching shell assets');
      cache.addAll(assets);
    })
  );
});
self.addEventListener('activate', evt => {
  evt.waitUntil(
    caches.keys().then(keys => {
      return Promise.all(keys
        .filter(key => key !== staticCacheName)
        .map(key => caches.delete(key))
      );
    })
  );
});
self.addEventListener('fetch', evt => {
  evt.respondWith(
    caches.match(evt.request).then(cacheRes => {
      return cacheRes || fetch(evt.request);
    })
  );
});
const dynamicCacheName = 'site-dynamic-v1';
self.addEventListener('activate', evt => {
  evt.waitUntil(
    caches.keys().then(keys => {
      return Promise.all(keys
        .filter(key =>  key !== dynamicCacheName)
        .map(key => caches.delete(key))
      );
    })
  );
});
self.addEventListener('fetch', evt => {
  evt.respondWith(
    caches.match(evt.request).then(cacheRes => {
      return cacheRes || fetch(evt.request).then(fetchRes => {
        return caches.open(dynamicCacheName).then(cache => {
          cache.put(evt.request.url, fetchRes.clone());
          return fetchRes;
        })
      });
    })
  );
});