I used Service Workers in production for a client to do offline mode and also to get truly instant page reload times for their SPA, which was important for kind of obscure reasons.
The Service Worker saved a complete HTML rendering of the current state of the React app, which was then served on reload, so that the correct view showed up even before any JavaScript was loaded.
Then in the next "requestIdleCallback", the React app was initialized with store data that was also cached.
It only works on Firefox and Chrome, so it's great for performance improvements or if you control the client's browser setup.
Other than that, try looking at your browser's debug pane for service workers and you'll see if any site has installed them. In my experience there are quite a few.
ProductHunt uses them to send notifications when you're off the site, which is a bit annoying, but maybe I said yes to it at some point...
The Service Worker saved a complete HTML rendering of the current state of the React app, which was then served on reload, so that the correct view showed up even before any JavaScript was loaded.
Then in the next "requestIdleCallback", the React app was initialized with store data that was also cached.
It only works on Firefox and Chrome, so it's great for performance improvements or if you control the client's browser setup.
Other than that, try looking at your browser's debug pane for service workers and you'll see if any site has installed them. In my experience there are quite a few.
ProductHunt uses them to send notifications when you're off the site, which is a bit annoying, but maybe I said yes to it at some point...