Component.js

import React, { Component }  from 'react';

import Menu, {SubMenu, MenuItem, Divider} from 'rc-menu';

export class Header extends Component {
  render() {
    return (
        <Menu>
          <MenuItem>1</MenuItem>
          <SubMenu title="2">
            <MenuItem>2-1</MenuItem>
          </SubMenu>
        </Menu>
    );
  }
}