Request: isHistoryNavigation プロパティ

self.addEventListener("request", (event) => {
  // ...
  if (event.request.isHistoryNavigation) {
    event.respondWith(
      caches.match(event.request).then((response) => {
        if (response !== undefined) {
          return response;
        } else {
          return fetch(event.request).then((response) => {
            let responseClone = response.clone();
            caches.open("v1").then((cache) => {
              cache.put(event.request, responseClone);
            });
            return response;
          });
        }
      }),
    );
  }
  // ...
});