使用Bootstarp 4中的rounded-top类可为元素设置顶部圆角。
使用该类，我使用相同的类设置了两个矩形-
<div class="new rounded-top"></div> <div class="new rounded-top"></div>
还为div设置了一个新类来对其进行样式设置，
<style>
.new {
width: 60px;
height: 60px;
background-color: #26CF12;
margin: 20px;
}
</style>您可以尝试运行以下代码来实现Rounded-top类-
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css">
<script src="https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>
<style>
.new {
width: 60px;
height: 60px;
background-color: #26CF12;
margin: 20px;
}
</style>
</head>
<body>
<div class="container">
<h2>Rounded Corner</h2>
<p>We have two rectangles with top rounded corner:</p>
<div class="new rounded-top"></div>
<div class="new rounded-top"></div>
</div>
</body>
</html>