sw_cached_site.js

// cache name
const cacheName = "offline-cache-v2";

// Call Install Event
self.addEventListener("install", (e) => {
  console.log("Service Worker Installed");
});

// Call Activate Event
self.addEventListener("activate", (e) => {
  console.log("Service Worker Activated");
  //   Remove unwanted caches
  e.waitUntil(
    caches.keys().then((cacheNames) => {
      return Promise.all(
        cacheNames.map((cache) => {
          if (cache !== cacheName) {
            console.log("Service Worker clearing Old Cache");
            return caches.delete(cache);
          }
        })
      );
    })
  );
});

// Call Fetch Event
self.addEventListener("fetch", (e) => {
  console.log("Service Worker: Fetching");
  e.respondWith(
    fetch(e.request)
      .then((res) => {
        // Make a copy/clone response
        const resClone = res.clone();
        // Open cache
        return caches.open(cacheName).then((cache) => {
          // add response to cache
          cache.put(e.request, resClone);
          return res;
        });
      })
      .catch((err) => {
        console.error("Fetch Error:", err);
        return caches.match(e.request);
      })
  );
});