const initialState = { count: 0 };

function reducer(state, action) {
  switch (action.type) {
    case 'increment':
      return { count: state.count + 1 };
    case 'decrement':
      return { count: state.count - 1 };
  }
}

function Counter() {
  const [ state, dispatch ] = useReducer(reducer, initialState);
  const increment = () => dispatch({ type: 'increment' });
  const decrement = () => dispatch({ type: 'decrement' });
  return (
    <>
      Count: {state.count}
      <button onClick={increment}>+</button>
      <button onClick={decrement}>-</button>
    </>
  );
}