It's time for Service Workers

index.html

@@ -143,6 +143,14 @@ <h1>About</h1>
 		ga('send', 'event', 'App', 'Theme', theme);
 	}, 2000);
 })(document, navigator.userAgent);
+
+if ('serviceWorker' in navigator){
+	navigator.serviceWorker.register('service-worker.js').then(function(registration){
+		console.log('ServiceWorker registration successful with scope: ', registration.scope);
+	}).catch(function(err){
+		console.log('ServiceWorker registration failed: ', err);
+	});
+}
 </script>
 </body>
 </html>

service-worker.js

@@ -0,0 +1,63 @@
+self.addEventListener('install', function(event){
+	console.log('Install');
+});
+
+self.addEventListener('activate', function(event){
+	console.log('Activate');
+});
+
+var cacheName = 'hackerweb-v1';
+var successResponses = /^0|([123]\d\d)|(40[14567])|410$/;
+var networkTimeoutSeconds = 10;
+
+function fetchAndCache(request){
+	console.log('fetchAndCache', request.url);
+	return fetch(request.clone()).then(function(response){
+		console.log(request.method, request.url, response.status, response.type);
+		if (request.method == 'GET' && response && successResponses.test(response.status) && response.type == 'basic'){
+			console.log('Cache', request.url);
+			caches.open(cacheName).then(function(cache){
+				cache.put(request, response);
+			});
+		}
+		return response.clone();
+	});
+};
+
+function cacheOnly(request){
+	console.log('cacheOnly', request.url);
+	return caches.open(cacheName).then(function(cache){
+		return cache.match(request);
+	});
+};
+
+// Fastest strategy from https://github.com/GoogleChrome/sw-toolbox
+self.addEventListener('fetch', function(event){
+	var request = event.request;
+	var url = request.url;
+	console.log('Fetch', url);
+	event.respondWith(new Promise(function(resolve, reject){
+		var rejected = false;
+		var reasons = [];
+
+		var maybeReject = function(reason){
+			reasons.push(reason.toString());
+			if (rejected){
+				reject(new Error('Both cache and network failed: "' + reasons.join('", "') + '"'));
+			} else {
+				rejected = true;
+			}
+		};
+
+		var maybeResolve = function(result){
+			if (result instanceof Response){
+				resolve(result);
+			} else {
+				maybeReject('No result returned');
+			}
+		};
+
+		fetchAndCache(request.clone()).then(maybeResolve, maybeReject);
+		cacheOnly(request).then(maybeResolve, maybeReject);
+	}));
+});