无法访问redux store react中的数据

import React from 'react';
import ReactDOM from 'react-dom';
import { Provider } from 'react-redux';
import store from './store'; // 导入Redux Store

ReactDOM.render(
  <Provider store={store}>
    <App />
  </Provider>,
  document.getElementById('root')
);

import React from 'react';
import { connect } from 'react-redux';

const MyComponent = ({ data }) => {
  // 使用Redux Store中的数据
  return (
    <div>
      <h1>{data}</h1>
    </div>
  );
};

const mapStateToProps = (state) => {
  return {
    data: state.data // 将Redux Store中的data状态映射到组件的props中
  };
};

export default connect(mapStateToProps)(MyComponent);

import { createStore } from 'redux';

// 定义初始状态
const initialState = {
  data: null
};

// 定义Reducer
const reducer = (state = initialState, action) => {
  switch (action.type) {
    case 'UPDATE_DATA':
      return {
        ...state,
        data: action.payload
      };
    default:
      return state;
  }
};

// 创建Redux Store
const store = createStore(reducer);

export default store;