Reselect createSelector

Helper for grabbing data from a Redux store.

Takes in two arguments, the first is an array of 'input selectors' (functions which take in RootState). The second is a 'result function', which takes the result of the input selectors as its arguments, and returns the final value.

const getFavoriteFruitPrice = createSelector(
    [
        (state: RootState) => state.user.favorites.fruit,
        (state: RootState) => state.shelf.prices,
    ],
    (prices: Record<Fruit, number>, favorite: Fruit) => {
        return prices[favorite];
    }
);

See Selectors Redux documentation for more general info on selectors

See Reselect createSelector documentation