docs(react): clarify state behavior with Ionic React

docs/react/lifecycle.md

@@ -145,3 +145,13 @@ Below are some tips on use cases for each of the life cycle events.
 - `ionViewDidEnter` - If you see performance problems from using `ionViewWillEnter` when loading data, you can do your data calls in `ionViewDidEnter` instead. This event won't fire until after the page is visible to the user, however, so you might want to use either a loading indicator or a skeleton screen, so content doesn't flash in un-naturally after the transition is complete.
 - `ionViewWillLeave` - Can be used for cleanup, like unsubscribing from data sources. Since `componentWillUnmount` might not fire when you navigate from the current page, put your cleanup code here if you don't want it active while the screen is not in view.
 - `ionViewDidLeave` - When this event fires, you know the new page has fully transitioned in, so any logic you might not normally do when the view is visible can go here.
+
+## Passing state between pages
+
+Since Ionic React manages the lifetime of a page, state on previous pages may update as users navigate your application. This can impact state that is determined using `useEffect` from React or `useLocation` from React Router. For example, if `PageA` calls `useLocation`, the state of `useLocation` will change when the user navigates from `PageA` to `PageB`.
+
+Developers should include the appropriate checks to ensure that previous pages only access defined states.
+
+For example, the following code will error if `testObject` is not defined: `{ state.testObject.childKey }`
+
+Instead, developers should access `childKey` only if `testObject` is defined: `{ state.testObject?.childKey }`