React门户是React框架中的一种特殊组件，用于将子组件渲染到指定的DOM节点上。React门户通常用于创建弹出框、模态框、菜单等需要脱离父组件的DOM结构的情况。在React门户中，可以使用无状态功能组件（SFC）来定义子组件。

javascript
import React from 'react';
import ReactDOM from 'react-dom';
const Modal = ({ isOpen, onClose, children }) => {
  if (!isOpen) return null;
  return ReactDOM.createPortal(
    
      
        
          Close
        
        {children}
      
    
,
    document.getElementById('modal-root')
  );
};
const App = () => {
  const [isModalOpen, setIsModalOpen] = React.useState(false);
  const handleOpenModal = () => {
    setIsModalOpen(true);
  };
  const handleCloseModal = () => {
    setIsModalOpen(false);
  };
  return (
    
      
React Portal Example
      Open Modal
      
        
Modal Content
        
This is an example of using React Portal with a modal component.
      
    
  );
};
ReactDOM.render(, document.getElementById('root'));

Modal Content