必须包装在封闭标签中

我在创建一个简单的组件以在我的React应用程序中呈现菜单时遇到麻烦。

这是我的组件的代码：

import React, { Component } from 'react';

export default class menu extends Component {

    render() {
        return (
            <nav className="navbar navbar-expand-lg navbar-light bg-light">
                <a className="navbar-brand" href="#">Navbar</a>
                <button className="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
                    <span className="navbar-toggler-icon"></span>
                </button>
                <div className="collapse navbar-collapse" id="navbarNavDropdown">
                    <ul className="navbar-nav">
                        <li className="nav-item active">
                            <a className="nav-link" href="#">Home <span className="sr-only">(current)</span></a>
                        </li>
                        <li className="nav-item">
                            <a className="nav-link" href="#">Features</a>
                        </li>
                        <li className="nav-item">
                            <a className="nav-link" href="#">Pricing</a>
                        </li>
                        <li className="nav-item dropdown">
                            <a className="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                                Dropdown link
                            </a>
                            <div className="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
                                <a className="dropdown-item" href="#">Action</a>
                                <a className="dropdown-item" href="#">Another action</a>
                                <a className="dropdown-item" href="#">Something else here</a>
                            </div>
                        </li>
                    </ul>
                </div>
            </nav>
        );
    }

}

我将其放在其他组件中。

import menu from './componentes/menu';

构造器（props）{超级（props）this.state = {sistemas：[]}; }

class App extends Component {

render() {
    return (
      <div>
        <menu></menu>
      </div>
      <div className="App">

        <div className="bs-header" id="content">
          <div className="container">
            <h1>Template Changelog</h1>
            <p>Lists all changes to the HTML template files</p>
          </div>
        </div>

); //[js] JSX expressions must have one parent element.
  }

}

我也在注释行中收到以下错误

[js] JSX表达式必须具有一个父元素。