surma

// Implements stale-while-revalidate
self.addEventListener('fetch', event => {
  const cached = caches.match(event.request);
  const fetched = fetch(event.request);
  const fetchedCopy = fetched.then(resp => resp.clone());

  // Call respondWith() with whatever we get first.
  // If the fetch fails (e.g disconnected), wait for the cache.
  // If there’s nothing in cache, wait for the fetch. 
  // If neither yields a response, return a 404.