哪吒面板右下角添加 回到顶部 按钮

<style>
        body {
            overflow-y: scroll;
        }
</style>
<!-- 返回顶部按钮 -->
<button id="topBtn" class="top-btn" style="display: none; position: fixed; bottom: 20px; right: 20px; z-index: 9999; background-color: #ffcc00; color: white; border: none; border-radius: 50%; width: 40px; height: 40px; font-size: 20px; display: flex; align-items: center; justify-content: center; cursor: pointer;">▲</button>

<script>
    // 获取返回顶部按钮
    const topBtn = document.getElementById('topBtn');

    // 当DOM加载完成后执行
    document.addEventListener('DOMContentLoaded', function() {
        // 监听滚动事件
        window.onscroll = function() {
            scrollFunction();
        };

        // 显示或隐藏返回顶部按钮
        function scrollFunction() {
            if (document.body.scrollTop > 20 || document.documentElement.scrollTop > 20) {
                topBtn.style.display = "block";
            } else {
                topBtn.style.display = "none";
            }
        }

        // 当点击按钮时滚动到顶部
        topBtn.addEventListener('click', function() {
            document.body.scrollTop = 0; // 对于 Safari
            document.documentElement.scrollTop = 0; // 对于 Chrome, Firefox, IE 和 Opera
        });
    });
</script>