pwabuilder-sw.js

//This is the "Offline page" service worker

//Install stage sets up the offline page in the cahche and opens a new cache
self.addEventListener('install', function(event) {
    var offlinePage = new Request('index.php');
    event.waitUntil(
        fetch(offlinePage).then(function(response) {
            return caches.open('pwabuilder-offline').then(function(cache) {
                console.log('[PWA Builder] Cached offline page during Install'+ response.url);
                return cache.put(offlinePage, response);
            });
        }));
});

//If any fetch fails, it will show the offline page.
//Maybe this should be limited to HTML documents?
self.addEventListener('fetch', function(event) {
    event.respondWith(
        fetch(event.request).catch(function(error) {
            console.error( '[PWA Builder] Network request Failed. Serving offline page ' + error );
            return caches.open('pwabuilder-offline').then(function(cache) {
                return cache.match('offline.html');
            });
        }));
});

//This is a event that can be fired from your page to tell the SW to update the offline page
self.addEventListener('refreshOffline', function(response) {
    return caches.open('pwabuilder-offline').then(function(cache) {
        console.log('[PWA Builder] Offline page updated from refreshOffline event: '+ response.url);
        return cache.put(offlinePage, response);
    });
});