swCopy

self.addEventListener("activate", function(evt) {
    console.log("[ServiceWorker] Activated")

    evt.waitUntil(

        caches.keys().then(function(cacheNames) {
            return Promise.all(cacheNames.map(function(thisCacheName) {

                if (thisCacheName !== cacheName) {
                    console.log("[ServiceWorker] Removing cached files from", thisCacheName);
                    return caches.delete(thisCacheName);
                }

            }))
        })

    )
})

self.addEventListener("fetch", function(evt) {
    console.log("[ServiceWorker] Fetching", evt.request.url);

    if (!(evt.request.url.indexOf('http') === 0)) {
        return;
    } 

    evt.respondWith(

        caches.match(evt.request).then(function(response) {

            if (response) {
                console.log("[ServiceWorker] Found in cache", evt.request.url);
                return response;
            }

            var requestClone = evt.request.clone();

            fetch(requestClone)
                .then(function(response) {

                    if (!response) {
                        console.log("[ServicerWorker] No response from fetch")
                        return response;
                    }

                })

            var responseClone = response.clone();

            caches.open(cacheName).then(function(cache) {

                cache.put(e.request, responseClone);
                limitCacheSize(cacheName, 100);
                return response;

            })

        })
        .catch(function(err) {
            console.log("[ServiceWorker] Error Fetching & Caching new version.")
            caches.match("/fallback")
        })

    )
})

//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));
            }
        })
    })
}