React Hooks: useReducer with actions and selectors (Redux-like)

hooks.js

function useSelectors(reducer, mapStateToSelectors) {
  const [state] = reducer;
  const selectors = useMemo(() => mapStateToSelectors(state), [state]);
  return selectors;
}

function useActions(reducer, mapDispatchToActions) {
  const [, dispatch] = reducer;
  const actions = useMemo(() => mapDispatchToActions(dispatch), [dispatch]);
  return actions;
}

const initialState = { count: 0 };

function reducer(state = initialState, action) {
  switch(action.type) {
    case 'increment':
    case 'decrement':
      return { count: state.count + action.amount };
  }
}

function Example() {
  const counterReducer = useReducer(reducer, initialState);
  const { increment, decrement } = useActions(counterReducer, (dispatch) => ({
    increment: (amount) => dispatch({ type: 'increment', amount || 1 }),
    decrement: (amount) => dispatch({ type: 'decrement', amount: -(amount || 1) })
  }));
  const { getCount, getDividedBy } = useSelectors(counterReducer, (state) => ({
    getCount: () => state,
    getDividedBy: (amount) => state.count / amount
  }));

  return (
    <div>
      <p>Current count is {getCount()} and divided by two: {getDividedBy(2)}</p>
      <button onClick={() => increment(1)}>+</button>
      <button onClick={() => decrement(1)}>-</button>
    </div>
  )
}