self.addEventListener("fetch", function(event) { if (event.request.url.includes("index.html")) { event.respondWith(fetch("realindex.html")); } else if (event.request.url.includes("image-20px.png")) { if (event.request.url.indexOf("https://") == 0) { event.respondWith(fetch("image-40px.png")); } else { event.respondWith(Response.error()); } } });