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An attempt at a minimal viable service worker.
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// Licensed under a CC0 1.0 Universal (CC0 1.0) Public Domain Dedication | |
// http://creativecommons.org/publicdomain/zero/1.0/ | |
// HTML files: try the network first, then the cache. | |
// Other files: try the cache first, then the network. | |
// Both: cache a fresh version if possible. | |
// (beware: the cache will grow and grow; there's no cleanup) | |
const cacheName = 'files'; | |
addEventListener('fetch', fetchEvent => { | |
const request = fetchEvent.request; | |
if (request.method !== 'GET') { | |
return; | |
} | |
fetchEvent.respondWith(async function() { | |
const fetchPromise = fetch(request); | |
fetchEvent.waitUntil(async function() { | |
const responseFromFetch = await fetchPromise; | |
const responseCopy = responseFromFetch.clone(); | |
const myCache = await caches.open(cacheName); | |
return myCache.put(request, responseCopy); | |
}()); | |
if (request.headers.get('Accept').includes('text/html')) { | |
try { | |
return await fetchPromise; | |
} | |
catch(error) { | |
return caches.match(request); | |
} | |
} else { | |
const responseFromCache = await caches.match(request); | |
return responseFromCache || fetchPromise; | |
} | |
}()); | |
}); |
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Just to note that the main gist here is missing an
await
in the "return fetchPromise" line (as given in @jakearchibald's update), which means as-is it won't respond from the cache for HTML pages - as the promise can always be returned so will be, regardless of whether it resolves or rejects.