HTML侧菜单(垂直)在页面加载时滚动到活动项目

<div id="sidebar">
  <ul>
    <li id="item1">菜单项1</li>
    <li id="item2">菜单项2</li>
    <li id="item3">菜单项3</li>
    <li id="item4">菜单项4</li>
  </ul>
</div>

#sidebar {
  height: 400px;
  overflow-y: scroll;
}

#sidebar ul {
  list-style-type: none;
  padding: 0;
  margin: 0;
}

#sidebar li {
  padding: 10px;
  background-color: #f0f0f0;
  cursor: pointer;
}

#sidebar li:hover {
  background-color: #ccc;
}

window.addEventListener('load', function() {
  var activeItem = document.getElementById('item3'); // 假设活动项目是菜单项3
  activeItem.scrollIntoView();
});