self.addEventListener("install", event => {
  console.log("installing...");
});

self.addEventListener("activate", event => {
  console.log("activate!");
});

self.addEventListener("fetch", event => {
  console.log("start service worker");

  event.respondWith(
    fetch(event.request).then(response => {
      console.log("fetching %s", event.request.url);
      return response;
    })
  );
});