sblum-pwa--service-worker-code2.js

// Cleanup old cache storages
    self.addEventListener("activate", event => {
    event.waitUntil(
        caches.keys()
            .then(cacheNames => {
            return Promise.all(
                cacheNames.map(cacheName => {
                    if (CACHE_VERSION !== cacheName) {
                        return caches.delete(cacheName);
                    }
                })
            );
        })
    );
});