14.13 Switching Case In Reducer

`reducer.js`

reducer.js
const initialState = {
  counter: 0,
};

const reducer = (state = initialState, action) => {
  switch (action.type) {
    case "INCREMENT":
      return {
        counter: state.counter + 1,
      };
    case "DECREMENT":
      return {
        counter: state.counter - 1,
      };

    case "ADD":
      return {
        counter: state.counter + action.value,
      };

    case "SUBTRACT":
      return {
        counter: state.counter - action.value,
      };
    default:
      return {
        counter: state.counter,
      };
  }
};

export default reducer;

reducer.js​

`reducer.js`