reducer in react example

1const initialState = {count: 0};
2
3function reducer(state, action) {
4  switch (action.type) {
5    case 'increment':
6      return {count: state.count + 1};
7    case 'decrement':
8      return {count: state.count - 1};
9    default:
10      throw new Error();
11  }
12}
13
14function Counter() {
15  const [state, dispatch] = useReducer(reducer, initialState);
16  return (
17    <>
18      Count: {state.count}
19      <button onClick={() => dispatch({type: 'decrement'})}>-</button>
20      <button onClick={() => dispatch({type: 'increment'})}>+</button>
21    </>
22  );
23}