ServiceWorker server vs. client request

proxy.js

self.onfetch = ev => {
    var serverReq = ev.request;
    var clientReq = new Request(serverReq.url, {
        method: serverReq.method,
        headers: serverReq.headers,
        mode: serverReq.mode,
        credentials: serverReq.credentials
    });

    serverReq.body.pipeTo(clientReq.body);

    // Note: lol, this re-uses a *client response* from fetch as a *server response*
    // out of the service worker. So all that work distinguishing between client vs.
    // server *requests* also needs to happen for response?!
    fetch(clientReq).then(clientRes => ev.respondWith(clientRes));
};