semaphore/templates/service-worker.js

79 lines
2.0 KiB
JavaScript

const timestamp = '__timestamp__';
const ASSETS = `cache${timestamp}`;
// `shell` is an array of all the files generated by webpack,
// `assets` is an array of everything in the `assets` directory
const to_cache = __shell__.concat(__assets__);
const cached = new Set(to_cache);
// `routes` is an array of `{ pattern: RegExp }` objects that
// match the pages in your app
const routes = __routes__;
self.addEventListener('install', event => {
event.waitUntil(
caches
.open(ASSETS)
.then(cache => cache.addAll(to_cache))
.then(() => {
self.skipWaiting();
})
);
});
self.addEventListener('activate', event => {
event.waitUntil(
caches.keys().then(async keys => {
// delete old caches
for (const key of keys) {
if (key !== ASSETS) await caches.delete(key);
}
await self.clients.claim();
})
);
});
self.addEventListener('fetch', event => {
const url = new URL(event.request.url);
// don't try to handle e.g. data: URIs
if (!url.protocol.startsWith('http')) return;
// always serve assets and webpack-generated files from cache
if (cached.has(url.pathname)) {
event.respondWith(caches.match(event.request));
return;
}
// for pages, you might want to serve a shell `index.html` file,
// which Sapper has generated for you. It's not right for every
// app, but if it's right for yours then uncomment this section
/*
if (url.origin === self.origin && routes.find(route => route.pattern.test(url.pathname))) {
event.respondWith(caches.match('/index.html'));
return;
}
*/
// for everything else, try the network first, falling back to
// cache if the user is offline. (If the pages never change, you
// might prefer a cache-first approach to a network-first one.)
event.respondWith(
caches
.open(`offline${timestamp}`)
.then(async cache => {
try {
const response = await fetch(event.request);
cache.put(event.request, response.clone());
return response;
} catch(err) {
const response = await cache.match(event.request);
if (response) return response;
throw err;
}
})
);
});