Implicit updates
"The Service Worker Lifecycle" is a great resource for these types of questions.
In particular, there's a section dealing with updates:
An update is triggered:
- On navigation to an in-scope page.
- On functional events such as push and sync, unless there's been an update check within the previous 24 hours.
- On calling .register() only if the service worker URL has changed.
Explicit updates
Because your SPA doesn't use real navigations, you won't get the automatic update checks mentioned in the first bullet point.
What you can do instead is follow the example from later on in that section:
As I mentioned earlier, the browser checks for updates automatically
after navigations and functional events, but you can also trigger them
manually:
navigator.serviceWorker.register('/sw.js').then(reg => {
// sometime later…
reg.update();
});
What I'd probably do is to modify your SPA's router and automatically make a call to reg.update() whenever your router is about to switch to a new view. That would simulate the same update-on-navigation behavior that you'd get in a non-SPA.
How does register() fit in?
After at least one call to navigator.serviceWorker.register() has been made, the service worker has a chance to install and activate. At this point, checks for service worker updates will happen irrespective of whether or not navigator.serviceWorker.register() is called again.
The earlier sections of this answer describe when these update checks will take place, either implicitly or explicitly.
You can dive into the details of this by comparing the differences between the Register and Update jobs in the service worker specification.
