Counter_useReducer.js

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};
    case 'set':
      return {count: action.count};
    case 'reset':
      return initialState;
    default:
      state;
  }
}
function Counter() {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({type: 'reset'})}>Reset</button>
      <button onClick={() => dispatch({type: 'decrement'})}>-</button>
      <button onClick={() => dispatch({type: 'increment'})}>+</button>
      <button onClick={() => dispatch({type: 'set', count: 25})}>Set to 25</button>
    </>
  );
}