After a service worker is installed and the user navigates to a different page or refreshes, the service worker will begin to receive fetch
events.
A fetch
event fires every time any resource controlled by a service worker is fetched, which includes the documents inside the specified scope, and any resources referenced in those documents (for example if index.html makes a cross origin request to embed an image, that still goes through its service worker.)
Consider:
self.addEventListener('fetch', function(event) {
event.respondWith(
caches.match(event.request)
.then(function(response) {
// Cache hit - return response
if (response) {
return response;
}
return fetch(event.request);
}
)
);
});