self.addEventListener("fetch", async e => { if (e.request.url.endsWith("ping")) e.respondWith(new Response('pong')); else if (e.request.url.endsWith("client")) { e.respondWith((async () => { const client = await clients.get(e.clientId); const clientInfo = client ? {id: e.clientId, visibilityState: client.visibilityState, focused: client.focused} : null; return new Response(JSON.stringify({clientInfo}), {headers: {'Content-Type': 'application/json'}}); })()); } });