addEventListener("activate", event => { event.waitUntil(self.registration.navigationPreload.enable()); }); async function post_to_page(data) { let cs = await self.clients.matchAll(); for (const client of cs) { client.postMessage(data); } } addEventListener("fetch", event => { if (event.request.url.includes("navigationPreload_page.html")) { event.respondWith( new Response("", { headers: { "Content-Type": "text/html; charset=utf-8" }, }) ); event.waitUntil( (async function() { let preloadResponse = await event.preloadResponse; let text = await preloadResponse.text(); await post_to_page(text); })() ); } });