向元素添加红色背景色以使用Bootstrap设置危险动作
使用.btn-danger类可以为按钮设置危险动作，即元素的红色背景色。
您可以尝试运行以下代码来实施危险动作-
示例
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap Example</title>
<link href = "/bootstrap/css/bootstrap.min.css" rel = "stylesheet">
<script src = "/scripts/jquery.min.js"></script>
<script src = "/bootstrap/js/bootstrap.min.js"></script>
</head>
<body>
<div class = "container">
<button type = "button" class = "btn btn-primary btn-block">Categories</button>
</div>
<div class = "container">
<a href = "#">Tech <span class="badge">95</span></a><br>
<a href = "#">Entertainment <span class="badge">30</span></a><br>
<a href = "#">Research <span class="badge">9</span></a><br>
<a href = "#">Viral <span class="badge">20</span></a><br>
<a href = "#">Sport <span class="badge">105</span></a>
</div>
<div class = "container">
<br><p>Do not click below:</p>
<button type = "button" class = "btn btn-danger">Danger</button>
</div>
</body>
</html>