引导程序助手类
Bootstrap中的帮助程序类包括pull-left，.pull-right，.center-block和其他类。
让我们看一个.clearfix类的例子-
要清除任何元素的浮点数，请使用.clearfix类-
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 = "clearfix" style = "background: orange;border: 1px solid #000; padding: 10px;">
<div class = "pull-left" style = "background:#58D3F7;">
Quick Float to left
</div>
<div class = "pull-right" style = "background: #DA81F5;">
Quick Float to right
</div>
</div>
</body>
</html>