tenacitOS/public/sw.js

const CACHE = "mc-v1";
self.addEventListener("install", e => { self.skipWaiting(); });
self.addEventListener("activate", e => { e.waitUntil(clients.claim()); });
self.addEventListener("fetch", e => {
  const url = new URL(e.request.url);
  if (url.pathname.startsWith("/api/")) {
    e.respondWith(fetch(e.request).catch(() => caches.match(e.request)));
  } else {
    e.respondWith(caches.match(e.request).then(r => r || fetch(e.request).then(res => {
      const clone = res.clone();
      caches.open(CACHE).then(c => c.put(e.request, clone));
      return res;
    })));
  }
});