Bootstrap .btn-xs类
要创建额外的小按钮，请使用.btn-xs类。
您可以尝试运行以下代码以在Bootstrap中实现btn-xs类-
示例
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap Example</title>
<meta name = "viewport" content = "width = device-width, initial-scale = 1">
<link rel = "stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css">
<script src = "https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script>
<script src = "https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
</head>
<body>
<p>The following are extra small buttons:</p>
<button type = "button" class = "btn btn-primary btn-xs">
Extra small Primary button
</button>
<button type = "button" class = "btn btn-default btn-xs">
Extra small button
</button>
</body>
</html>