ReactDOM.render(
 <React.StrictMode>
  <TodoList />
 </React.StrictMode>,
 document.getElementById('root')
);

constructor(props) {
    super(props);
    this.state = {
      inputValue: '',
      list: []
    }
  }

 render() {
    return (
      <React.Fragment>
        <div>
          {/*label标签的作用，扩大点击范围*/}
          <label htmlFor='insertArea'>输入内容</label>
          <input
            id='insertArea'
            className={'inputStyle'}
            value={this.state.inputValue}
            onChange={event => this.handleInputChangle(event)}/>
          <button onClick={event => this.handleButtonVlue(event)}>提交</button>
          <hr/>
          <ul>
            {this.getTodoList()}
          </ul>
        </div>
      </React.Fragment>
    )
  }

getTodoList() {
    return (
      this.state.list.map((value, index) => {
        return <TodoItem2
          key={index}
          itemVlue={value}
          itemIndex={index}
          itemDelete={this.handleItemDelete.bind(this)}>
          {/*这块需要强制绑定为父组件的this，否则在子组件中找不到*/}
        </TodoItem2>
      })
    );
  }

 /**
   * 监听输入框变化
   **/
  handleInputChangle(e) {
    const value = e.target.value;
    this.setState(() => ({
      inputValue: value
    }))
  }
 
  /**
   * 监听点击按钮
   **/
  handleButtonVlue(e) {
    this.setState((prevStatus) => ({
      list: [...prevStatus.list, this.state.inputValue],
      inputValue: ''
    }))
  }
 
  /**
   * 监听点击item删除
   **/
  handleItemDelete(index) {
    this.setState((preStatus) => {
      const list = [...preStatus.list];
      list.splice(index, 1)
      return {
        list
      }
    });
  }

 /**
   * 这块进行网络请求
   */
  componentDidMount() {
    axios.get('api/todolist')
      .then((res) => {
        this.setState({
          list: [...res.data]
        })
      }).catch(() => {
      alert('发生错误')
    })
  }