为什么我的redux reducer没有设置正确的状态？

const initialState = { count: 0 };
const store = createStore(reducer, initialState);

function counterReducer(state = initialState, action) {
  switch (action.type) {
    case 'INCREMENT':
      return { ...state, count: state.count + 1 };
    case 'DECREMENT':
      return { ...state, count: state.count - 1 };
    default:
      return state;
  }
}

function increment() {
  return { type: 'INCREMENT' };
}

function decrement() {
  return { type: 'DECREMENT' };
}

store.dispatch(increment());
console.log(store.getState()); // 应该显示 count 增加了

const store = createStore(reducer, initialState, window.__REDUX_DEVTOOLS_EXTENSION__ && window.__REDUX_DEVTOOLS_EXTENSION__());

function incrementAsync() {
  return dispatch => {
    setTimeout(() => {
      dispatch(increment());
    }, 1000);
  };
}