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π¨βπΌ When we hit the back/forward buttons, we're getting our suspense boundaries
for a bit. This is confusing because we've wrapped our content state update
in
startTransition which should keep the old UI around until the new one is
ready.This is actually intentional by the React team. They force suspense boundaries
to be shown when we hit the back/forward buttons if anything suspends to manage
things like scroll position and focus more accurately.
So what do we do? Well, we need to make it so our component doesn't suspend. We
do this by caching the content as the user navigates around, that way when they
go back/forward, we can just show the cached content.
The trick is, what should we use as the cache key? We can't use the URL because
the user could have navigated to the same URL multiple times in their history
and the content is not necessarily the same.
The
window.history API actually supports client-side state which the browser
will manage for us:window.history.pushState({ key: 'some-unique-key' }, '', '/some-url')
// then later
const key = window.history.state?.key
This is perfect. So we can simply generate a random ID, store the content
promise in a cache, then store the
contentKey in state instead of the
contentPromise directly. Then, whenever we navigate, or when popstate events
happen, we can create a new contentPromise and update the cache and cache key.π§ββοΈ I've implemented a special map that allows us to track whenever values change
in it so React will rerender our app when we update the cache. So you can get
the
contentCache directly from for
use in the module, but within the Root component, you can use the
useContentCache() hook to get a cache object that will trigger rerenders when
you update it.π¨βπΌ Great, thanks Kellie. Another thing you're going to want to do is make sure
when we land on the page, if the history doesn't already have a key, we generate
one, replace history with that key and get the content promise into the cache.
And in the
popstate case, if the key is already in the cache, we can just
update the contentKey in state and let the component rerender with the cached
content rather than fetching new content.
