可以利用类sticky-top实现固定某个元素在顶部的效果，示例代码如下：
<!DOCTYPE html>
<html>
<head><meta charset="UTF-8"><title>固定某一个元素不随滚动条滚动</title><meta name="viewport" content="width=device-width,initial-scale=1, shrink-to-fit=no"><link rel="stylesheet" href="bootstrap-4.5.3-dist/css/bootstrap.css"><script src="jquery-3.5.1.slim.js"></script><script src="bootstrap-4.5.3-dist/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container text-white"><nav class="sticky-top bg-primary p-5 mb-5">昊虹商城</nav><div class=" bg-secondary p-3"><p>家用电器</p><p>手机数码</p><p>家具家电</p><p>男装女装</p><p>男鞋户外</p><p>玩具乐器</p><p>生鲜特产</p><p>白酒红酒</p><p>礼品鲜花</p></div>
</div>
</body>
</html>
运行效果如下图所示：
