title: ReactJS Error: react/jsx-no-undef by react-bootstrap
body: <p>I want to use menu bar in my project. First, I choose it from <a href="https://react-bootstrap.github.io/components.html#navbars" rel="nofollow noreferrer">React-bootstrap</a> but program has show an error about 'react/jsx-no-undef'.</p>
  
  <p>This is code from <a href="https://react-bootstrap.github.io/components.html#navbars" rel="nofollow noreferrer">React-bootstrap</a> website.</p>
  
  <pre><code>const navbarInstance = (
  &lt;Navbar&gt;
      &lt;Navbar.Header&gt;
        &lt;Navbar.Brand&gt;
          &lt;a href="#"&gt;React-Bootstrap&lt;/a&gt;
        &lt;/Navbar.Brand&gt;
      &lt;/Navbar.Header&gt;
      &lt;Nav&gt;
        &lt;NavItem eventKey={1} href="#"&gt;Link&lt;/NavItem&gt;
        &lt;NavItem eventKey={2} href="#"&gt;Link&lt;/NavItem&gt;
        &lt;NavDropdown eventKey={3} title="Dropdown" id="basic-nav-dropdown"&gt;
          &lt;MenuItem eventKey={3.1}&gt;Action&lt;/MenuItem&gt;
          &lt;MenuItem eventKey={3.2}&gt;Another action&lt;/MenuItem&gt;
          &lt;MenuItem eventKey={3.3}&gt;Something else here&lt;/MenuItem&gt;
          &lt;MenuItem divider /&gt;
          &lt;MenuItem eventKey={3.4}&gt;Separated link&lt;/MenuItem&gt;
        &lt;/NavDropdown&gt;
      &lt;/Nav&gt;
    &lt;/Navbar&gt;
  );
  ReactDOM.render(navbarInstance, mountNode);
  </code></pre>