sw.js

importScripts('https://storage.googleapis.com/workbox-cdn/releases/4.3.1/workbox-sw.js');
if (workbox) {
	console.log(`Yay! Workbox is loaded 🎉`);
} else {
	console.log(`Boo! Workbox didn't load 😬`);
}
workbox.routing.registerRoute(
	new RegExp('.*\.js'),
	new workbox.strategies.NetworkFirst()
);
workbox.routing.registerRoute(
	// Cache CSS files.
	/\.css$/,
	// Use cache but update in the background.
	new workbox.strategies.StaleWhileRevalidate({
		// Use a custom cache name.
		cacheName: 'css-cache',
	})
);
workbox.routing.registerRoute(
	// Cache image files.
	/\.(?:png|jpg|jpeg|svg|gif)$/,
	// Use the cache if it's available.
	new workbox.strategies.CacheFirst({
		// Use a custom cache name.
		cacheName: 'image-cache',
		plugins: [
      new workbox.expiration.Plugin({
				// Cache only 20 images.
				maxEntries: 20,
				// Cache for a maximum of a week.
				maxAgeSeconds: 7 * 24 * 60 * 60,
			})
    ],
	})
);
workbox.precaching.precacheAndRoute([
    'index.css',
    'index.js',
	{
		url: 'index.html',
		revision: '383676'
	},
]);
var CACHE_VERSION = 1;
var CURRENT_CACHES = {
	prefetch: 'prefetch-cache-v' + CACHE_VERSION
};
self.addEventListener('install', function (event) {
	var now = Date.now();
	var urlsToPrefetch = [
    'index.html'
  ];
	// All of these logging statements should be visible via the "Inspect" interface
	// for the relevant SW accessed via chrome://serviceworker-internals
	console.log('Handling install event. Resources to prefetch:', urlsToPrefetch);
	event.waitUntil(
		caches.open(CURRENT_CACHES.prefetch).then(function (cache) {
			var cachePromises = urlsToPrefetch.map(function (urlToPrefetch) {
				// This constructs a new URL object using the service worker's script location as the base
				// for relative URLs.
				var url = new URL(urlToPrefetch, location.href);
				// Append a cache-bust=TIMESTAMP URL parameter to each URL's query string.
				// This is particularly important when precaching resources that are later used in the
				// fetch handler as responses directly, without consulting the network (i.e. cache-first).
				// If we were to get back a response from the HTTP browser cache for this precaching request
				// then that stale response would be used indefinitely, or at least until the next time
				// the service worker script changes triggering the install flow.
				url.search += (url.search ? '&' : '?') + 'cache-bust=' + now;
				// It's very important to use {mode: 'no-cors'} if there is any chance that
				// the resources being fetched are served off of a server that doesn't support
				// CORS (http://en.wikipedia.org/wiki/Cross-origin_resource_sharing).
				// In this example, www.chromium.org doesn't support CORS, and the fetch()
				// would fail if the default mode of 'cors' was used for the fetch() request.
				// The drawback of hardcoding {mode: 'no-cors'} is that the response from all
				// cross-origin hosts will always be opaque
				// (https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#cross-origin-resources)
				// and it is not possible to determine whether an opaque response represents a success or failure
				// (https://github.com/whatwg/fetch/issues/14).
				var request = new Request(url, {
					mode: 'no-cors'
				});
				return fetch(request).then(function (response) {
					if (response.status >= 400) {
						throw new Error('request for ' + urlToPrefetch +
							' failed with status ' + response.statusText);
					}
					// Use the original URL without the cache-busting parameter as the key for cache.put().
					return cache.put(urlToPrefetch, response);
				}).catch(function (error) {
					console.error('Not caching ' + urlToPrefetch + ' due to ' + error);
				});
			});
			return Promise.all(cachePromises).then(function () {
				console.log('Pre-fetching complete.');
			});
		}).catch(function (error) {
			console.error('Pre-fetching failed:', error);
		})
	);
});
self.addEventListener('activate', function (event) {
	// Delete all caches that aren't named in CURRENT_CACHES.
	// While there is only one cache in this example, the same logic will handle the case where
	// there are multiple versioned caches.
	var expectedCacheNames = Object.keys(CURRENT_CACHES).map(function (key) {
		return CURRENT_CACHES[key];
	});
	event.waitUntil(
		caches.keys().then(function (cacheNames) {
			return Promise.all(
				cacheNames.map(function (cacheName) {
					if (expectedCacheNames.indexOf(cacheName) === -1) {
						// If this cache name isn't present in the array of "expected" cache names, then delete it.
						console.log('Deleting out of date cache:', cacheName);
						return caches.delete(cacheName);
					}
				})
			);
		})
	);
});
self.addEventListener('fetch', function (event) {
	console.log('Handling fetch event for', event.request.url);
	event.respondWith(
		// caches.match() will look for a cache entry in all of the caches available to the service worker.
		// It's an alternative to first opening a specific named cache and then matching on that.
		caches.match(event.request).then(function (response) {
			if (response) {
				console.log('Found response in cache:', response);
				return response;
			}
			console.log('No response found in cache. About to fetch from network...');
			// event.request will always have the proper mode set ('cors, 'no-cors', etc.) so we don't
			// have to hardcode 'no-cors' like we do when fetch()ing in the install handler.
			return fetch(event.request).then(function (response) {
				console.log('Response from network is:', response);
				return response;
			}).catch(function (error) {
				// This catch() will handle exceptions thrown from the fetch() operation.
				// Note that a HTTP error response (e.g. 404) will NOT trigger an exception.
				// It will return a normal response object that has the appropriate error code set.
				console.error('Fetching failed:', error);
				throw error;
			});
		})
	);
});