代码示例：（标识：bs_form_input_group）
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/js/bootstrap.bundle.js"></script>
</head>
<body>
<div class="p-4">
<h2>输入组</h2>
<p>.input-group 类是一种容器，通过在输入字段的前面或后面添加图标、文本或按钮作为“帮助文本”来增强输入。</p>
<p>如需设置指定帮助文本的样式，请使用 .input-group-text 类：</p>
<form action=/index/demo/form_current.html>
<div class="input-group mb-3">
<span class="input-group-text">@</span>
<input type="text" class="form-control" placeholder="用户名" name="usrname">
</div>
<div class="input-group mb-3">
<input type="text" class="form-control" placeholder="您的电邮" name="email">
<span class="input-group-text">@example.com</span>
</div>
<button type="submit" class="btn btn-primary">提交</button>
</form>
</div>
</body>
</html>
