This example could be simplified somewhat if you're willing to leak the generated `ua` query parameter back to the origin server. Most servers will simply ignore unexpected query parameters, so this is likely to work fine.

In that case, you could change the fetch() call to:

    response = await fetch(newRequest);

And then make sure you set a page rule to "cache everything" on your whole site (otherwise by default HTML won't be cached since it's often dynamic).

Then you can remove the explicit `cache.match()` and `cache.put()` calls from this example, since the `fetch()` call will implicitly perform the caching you want.

(I'm the tech lead of Cloudflare Workers.)