sw.js

const staticCacheName = 'site-static-pwa-v1.0.0';
const dynamicCacheName = 'site-dynamic-pwa-v1.0.0';
const assets = [
	'/',
	'/index.html',
	'/Website-Assets/Styles/style-EmuFeral-Roadmap.css',
	'/offline.html',
	'/manifest.json'
]


// cache size limit function
const limitCacheSize = (name, size) => {
    caches.open(name).then(cache => {
        cache.keys().then(keys => {
            if (keys.length > size) {
                cache.delete(keys[0]).then(limitCacheSize(name, size));
            }
        });
    });
};

// install event
self.addEventListener('install', evt => {
    //console.log('service worker installed');
    evt.waitUntil(
        caches.open(staticCacheName).then((cache) => {
            console.log('caching shell assets');
            cache.addAll(assets);
        })
    );
});

// activate event
self.addEventListener('activate', evt => {
    //console.log('service worker activated');
    evt.waitUntil(
        caches.keys().then(keys => {
            //console.log(keys);
            return Promise.all(keys
                .filter(key => key !== staticCacheName && key !== dynamicCacheName)
                .map(key => caches.delete(key))
            );
        })
    );
});

// fetch event
self.addEventListener('fetch', evt => {
    //console.log('fetch event', evt);
    evt.respondWith(
        caches.match(evt.request).then(cacheRes => {
            return cacheRes || fetch(evt.request).then(fetchRes => {
                return caches.open(dynamicCacheName).then(cache => {
                    cache.put(evt.request.url, fetchRes.clone());
                    // check cached items size
                    limitCacheSize(dynamicCacheName, 7);
                    return fetchRes;
                })
            });
        }).catch(() => {
            if (evt.request.url.indexOf('.html') > 3) {
                return caches.match('/offline.html');
            }
        })
    );
});