In this example, I have shared What are selectors in redux?
getUser is not a reducer, it is indeed a selector, that is, a function that knows how to extract a specific piece of data from the store.
Selectors provide an additional layer such that if you altered your store structure and all of a sudden your users were no longer at
state.entities.users but instead at
state.users.objects.entities (or whatever) then you only need to update the getUser selector and not every place in your app where you were making a reference to the old location.
That makes them particularly handy when it comes to refactoring your Redux store.
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