Service worker installs via localhost, but fails when deployed to GitHub pages - service-worker

Question

I am working on a PWA and I have installed and activated a service worker on my site. It works perfectly well while testing on local server but when I ship my code live, it fails.
This is my SW:
const cacheName = 'v1';
const cacheFiles = [
'/',
'/css/styles.css',
'/images/test1.png',
'/images/test2.png',
'/js/app.js',
'/js/sw-registration.js'
]
// Install event
self.addEventListener('install', function(event) {
console.log("SW installed");
event.waitUntil(
caches.open(cacheName)
.then(function(cache){
console.log('SW caching cachefiles');
return cache.addAll(cacheFiles);
})
)
});
// Activate event
self.addEventListener('activate', function(event) {
console.log("SW activated");
event.waitUntil(
caches.keys()
.then(function(cacheNames){
return Promise.all(cacheNames.map(function(thisCacheName){
if(thisCacheName !== cacheName){
console.log('SW Removing cached files from', thisCacheName);
return caches.delete(thisCacheName);
}
}))
})
)
});
// Fetch event
self.addEventListener('fetch', function(event) {
console.log("SW fetching", event.request.url);
event.respondWith(
caches.match(event.request)
.then(function(response){
console.log('Fetching new files');
return response || fetch(event.request);
})
);
});
This is the error I'm getting:
Uncaught (in promise) TypeError: Request failed (sw.js:1)
I don't understand why it fails to cache my files online (github pages) when it works locally. Can someone help me understand?
Thank you.
EDIT: I tried to deploy the site via Netlify and it works there. So it has to be something to do with Github pages. I would still like to know what it is, if anyone can shed any light.

Answer 1

As mentioned in Service Worker caches locally but fails online, when deploying to gh-pages, your web app's content will normally be accessed from a subpath, not in the top-level path, for the domain.
For instance, if your files are in the gh-pages branch of https://github.com/<user>/<repo>, then your web content can be accessed from https://<user>.github.io/<repo>/.
All of the URLs in your cacheFiles array are prefixed with /, which isn't what you want, given that all of your content is accessible under /<repo>/. For instance, / is interpreted as https://<user>.github.io/, which is different from https://<user>.github.io/<repo>/.
The solution to your problem, which will lead to a configuration that works regardless of what the base URL is for your hosting environment, is to prepend each of your URLs with ./ rather than /. For instance:
const cacheFiles = [
'./',
'./css/styles.css',
// etc.
];
The ./ means that the URL is relative, with the location of the service worker file used as the base. Your service worker file will be deployed under https://<user>.github.io/<repo>/, so that will end up being the correct base URL to use for the rest of your content as well.