getSnapshotBeforeUpdate(prevProps: Readonly<P>, prevState: Readonly<S>): SS | null
Runs before React applies the result of render to the document, and
returns an object to be given to componentDidUpdate. Useful for saving
things such as scroll position before render causes changes to it.
Note: the presence of getSnapshotBeforeUpdate prevents any of the deprecated
lifecycle events from running.
Called immediately after updating occurs. Not called for the initial render.
The snapshot is only present if getSnapshotBeforeUpdate is present and returns non-null.