text: class PostList extends React.Component {
      constructor(props) {
          super(props);
          this.state = {
              postList: props.list,
              postListNow: []
          }
      }
      switchTab(id) {
          let _list = this.state.postList.filter(item => item.id === id);
          this.setState({
              postListNow: _list
          })
      }
      componentDidMount() {
          let _list = this.state.postList;
          this.setState({
              postListNow: _list
          })
      }
      render() {
          return (
              <div>
                  <a href="javascript:;" onClick={() => {
                      this.switchTab(1);
                  }}>第一章</a>
                  <a href="javascript:;" onClick={() => {
                      this.switchTab(2);
                  }}>第二章</a>
                  <a href="javascript:;" onClick={() => {
                      this.switchTab(3);
                  }}>第三章</a>
                  <ul>
                      {this.state.postListNow.map(item => <li key={item.id}>{item.title}</li>)}
                  </ul>
              </div>
          )
      }
  }
  export default  PostList;