如何使用React和iframe在点击时获取className？

import React, { useRef } from 'react';

const MyComponent = () => {
  const iframeRef = useRef(null);

  const handleClick = () => {
    const iframe = iframeRef.current;
    if (iframe) {
      const className = iframe.contentDocument.documentElement.className;
      console.log(className);
    }
  };

  return (
    <div>
      <button onClick={handleClick}>点击获取className</button>
      <iframe ref={iframeRef} src="https://example.com"></iframe>
    </div>
  );
};

export default MyComponent;