sw.js

//This is the "Offline copy of pages" service worker

//Install stage sets up the index page (home page) in the cache and opens a new cache
self.addEventListener('install', function(event) {
	var indexPage = new Request('index.html');
	event.waitUntil(
		fetch(indexPage).then(function(response) {
			return caches.open('pwabuilder-offline').then(function(cache) {
				return cache.put(indexPage, response);
			});
		})
	);
});

//If any fetch fails, it will look for the request in the cache and serve it from there first
self.addEventListener('fetch', function(event) {
	var updateCache = function(request) {
		return caches.open('pwabuilder-offline').then(function(cache) {
			return fetch(request).then(function(response) {
				return cache.put(request, response);
			});
		});
	};

	event.waitUntil(updateCache(event.request));

	event.respondWith(
		fetch(event.request).catch(function(error) {
			//Check to see if you have it in the cache
			//Return response
			//If not in the cache, then return error page
			return caches.open('pwabuilder-offline').then(function(cache) {
				return cache.match(event.request).then(function(matching) {
					var report =
						!matching || matching.status == 404
							? Promise.reject('no-match')
							: matching;
					return report;
				});
			});
		})
	);
});