Init commit

src/service-worker.js

@@ -0,0 +1,86 @@
+import { timestamp, files, shell } from '@sapper/service-worker';
+
+const ASSETS = `cache${timestamp}`;
+
+// `shell` is an array of all the files generated by the bundler,
+// `files` is an array of everything in the `static` directory
+const to_cache = shell.concat(files);
+const staticAssets = new Set(to_cache);
+
+self.addEventListener('install', event => {
+	event.waitUntil(
+		caches
+			.open(ASSETS)
+			.then(cache => cache.addAll(to_cache))
+			.then(() => {
+				self.skipWaiting();
+			})
+	);
+});
+
+self.addEventListener('activate', event => {
+	event.waitUntil(
+		caches.keys().then(async keys => {
+			// delete old caches
+			for (const key of keys) {
+				if (key !== ASSETS) await caches.delete(key);
+			}
+
+			self.clients.claim();
+		})
+	);
+});
+
+
+/**
+ * Fetch the asset from the network and store it in the cache. 
+ * Fall back to the cache if the user is offline.
+ */
+async function fetchAndCache(request) {
+	const cache = await caches.open(`offline${timestamp}`);
+
+	try {
+		const response = await fetch(request);
+		cache.put(request, response.clone());
+		return response;
+	} catch (err) {
+		const response = await cache.match(request);
+		if (response) return response;
+
+		throw err;
+	}
+}
+
+self.addEventListener('fetch', event => {
+	if (event.request.method !== 'GET' || event.request.headers.has('range')) return;
+
+	const url = new URL(event.request.url);
+
+	// don't try to handle e.g. data: URIs
+	const isHttp = url.protocol.startsWith('http');
+	const isDevServerRequest = url.hostname === self.location.hostname && url.port !== self.location.port;
+	const isStaticAsset = url.host === self.location.host && staticAssets.has(url.pathname);
+	const skipBecauseUncached = event.request.cache === 'only-if-cached' && !isStaticAsset;
+
+	if (isHttp && !isDevServerRequest && !skipBecauseUncached) {
+		event.respondWith(
+			(async () => {
+				// always serve static files and bundler-generated assets from cache.
+				// if your application has other URLs with data that will never change,
+				// set this variable to true for them and they will only be fetched once.
+				const cachedAsset = isStaticAsset && await caches.match(event.request);
+
+				// for pages, you might want to serve a shell `service-worker-index.html` file,
+				// which Sapper has generated for you. It's not right for every
+				// app, but if it's right for yours then uncomment this section
+				/*
+				if (!cachedAsset && url.origin === self.origin && routes.find(route => route.pattern.test(url.pathname))) {
+					return caches.match('/service-worker-index.html');
+				}
+				*/
+
+				return cachedAsset || fetchAndCache(event.request);
+			})()
+		);
+	}
+});