我如何让一个按钮出现在滚动上只使用‘普通’的html，CSS和Javascript

<div class="scroll-container">
  <button id="scroll-button">按钮</button>
</div>

.scroll-container {
  height: 300px; /* 设置滚动容器的高度 */
  overflow: scroll; /* 启用滚动 */
}

#scroll-button {
  display: none; /* 隐藏按钮 */
}

var scrollContainer = document.querySelector('.scroll-container');
var scrollButton = document.querySelector('#scroll-button');

scrollContainer.addEventListener('scroll', function() {
  if (scrollContainer.scrollTop > 0) {
    scrollButton.style.display = 'block'; // 显示按钮
  } else {
    scrollButton.style.display = 'none'; // 隐藏按钮
  }
});