sw_async-await.js

self.addEventListener('fetch', async (event) => {
  
  const response = await fetch(event.request);
  const cache = await caches.open('cache-v1');
  
  if (response.ok === true) {
    cache.put(event.request, response);
    event.respondWith(response);
  } else {
    event.respondWith(cache.match(event.request));
  }
});

sw_promise.js

self.addEventListener('fetch', (event) => {
  
  event.respondWith(
    fetch(event.request).then((response) => {
      return caches.open('cache-v1').then((cache) => {
        if (response.ok === true) {
          cache.put(event.request, response);
          return response;
        } else {
          return cache.match(event.request);
        }
      });
    }));
});