My scenario is the following:

1. I have a Progressive Web App that uses a Service Worker where I need to catch the request and do something with it every time the user requests a resource or leaves the current URL
2. I'm handling that through adding a callback to the fetch event of the worker
3. I only care about requested resources within our domain (e.g. example.com)
4. If the requested resource is within our domain I return the promise result from a regular fetch, so that's already covered
5. But, if the requested resource is outside my domain (as shown in the below snippet) I want the original request to just continue
6. I'm currently just doing a simple return if the scenario in bullet 5 is true

Snippet of my current code:

function onFetch(event) {
  if (!event.request.url.startsWith("example.com")) {
    return;
  } else {
    event.respondWith(
      fetch(event.request)
        .then(req => {
          // doing something with the request
        })
        .catch((error)=> {
          // handle errors etc.
        })
        .finally(()=> {
          // cleanup
        })
    );
  }
}

self.addEventListener('fetch', onFetch);

My question: Is it OK if I just return nothing like in the snippet, or, do I need to return something specific, like a new promise by fetching the original request (like I'm doing on the else block)?

Thanks!