监听onclick事件判断鼠标是否点在区域外

 componentWillUnmount() {
    document.removeEventListener('mousedown', (e) => this.handleClick(e), false);
  }

  componentDidMount() {
    document.addEventListener('mousedown', (e) => this.handleClick(e), false);
  }
 
  handleClick(e) {
    //点在dropdown外面关闭menu菜单
    if (!ReactDOM.findDOMNode(this.dropdown.ref).contains(e.target)) {
      this.setState({open: false})
    }
  }