UDN/static/dist/sw.js

const CACHE_VERSION = "v1";

async function handleRequest(event) {
  const responsePromise = getResponse(event);
  event.respondWith(responsePromise);
}

async function getResponse(event) {
  try {
    return await fetchAndCache(event);
  } catch {
    return await getFromCache(event);
  }
}

async function fetchAndCache(event) {
  const request = event.request;

  const response = await fetch(request);

  const cache = await caches.open(CACHE_VERSION);
  await cache.put(request, response.clone());

  return response;
}

async function getFromCache(event) {
  const request = event.request;

  const cache = await caches.open(CACHE_VERSION);
  const response = await cache.match(request);

  return response;
}

self.addEventListener("fetch", (event) => {
  handleRequest(event);
});