嘿，我正在尝试制作一个基本的 React 滚动到顶部按钮，我从 w3 获得了此代码，我认为它很好，我尝试更改一些东西，但没有成功，我相信解决方案很愚蠢，希望得到帮助，谢谢。我收到此错误：

Cannot set property 'display' of undefined

这是我的代码：

import React, { useRef } from "react";

const ScrollToTop = () => {
  const myButton = useRef(null);

  // When the user scrolls down 20px from the top of the document, show the button
  window.onscroll = function () {
    scrollFunction();
  };

  function scrollFunction() {
    if (
      document.body.scrollTop > 20 ||
      document.documentElement.scrollTop > 20
    ) {
      myButton.style.display = "block";
    } else {
      myButton.style.display = "none";
    }
  }

  // When the user clicks on the button, scroll to the top of the document
  function topFunction() {
    document.body.scrollTop = 0; // For Safari
    document.documentElement.scrollTop = 0; // For Chrome, Firefox, IE and Opera
  }
  return (
    <div>
      <button onclick="topFunction()" ref={myButton} title="Go to top">
        Top
      </button>
    </div>
  );
};

export default ScrollToTop;