44 lines
1.7 KiB
JavaScript
44 lines
1.7 KiB
JavaScript
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// Incrementing OFFLINE_VERSION will kick off the install event and force
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// previously cached resources to be updated from the network.
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const OFFLINE_VERSION = 1;
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const CACHE_NAME = "offline";
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self.addEventListener("install", (event) => {
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event.waitUntil(
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(async () => {
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const cache = await caches.open(CACHE_NAME);
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// Setting {cache: 'reload'} in the new request will ensure that the
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// response isn't fulfilled from the HTTP cache; i.e., it will be from
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// the network.
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await cache.add(new Request(OFFLINE_URL, { cache: "reload" }));
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})()
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);
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// Force the waiting service worker to become the active service worker.
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self.skipWaiting();
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});
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self.addEventListener("fetch", (event) => {
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// We proxify requests through fetch() only if we are offline because it's slower.
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if (navigator.onLine === false && event.request.mode === "navigate") {
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event.respondWith(
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(async () => {
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try {
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// Always try the network first.
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const networkResponse = await fetch(event.request);
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return networkResponse;
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} catch (error) {
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// catch is only triggered if an exception is thrown, which is likely
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// due to a network error.
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// If fetch() returns a valid HTTP response with a response code in
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// the 4xx or 5xx range, the catch() will NOT be called.
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const cache = await caches.open(CACHE_NAME);
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const cachedResponse = await cache.match(OFFLINE_URL);
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return cachedResponse;
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}
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})()
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);
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}
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});
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