<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<link rel="stylesheet" href="bootstrap/css/bootstrap.min.css">
<script src="bootstrap/js/jquery-3.4.1.js"></script>
<script src="bootstrap/js/bootstrap.js"></script>
</head>
<body>
<div class="container">
<form action="">
<h2>默认</h2>
<label for="user">用户名</label>
<input type="text">
<h2>.form-control</h2>
<label for="user">用户名</label>
<input type="text" class="form-control">
<h2>.form-group .form-control 配合 id 使用，点击用户名则可以唤起输入</h2>
<div class="form-group">
<label for="user">用户名</label>
<input type="text" class="form-control" id="user" placeholder="用户名">
</div>
<div class="form-group">
<label for="pass">密码</label>
<input type="text" class="form-control" id="pass" placeholder="密码">
</div>
<h2>.sr-only </h2>
<div class="form-group">
<label for="user" class="sr-only">用户名</label>
<input type="text" class="form-control" id="user" placeholder="用户名">
</div>
<div class="form-group">
<label for="pass" class="sr-only">密码</label>
<input type="text" class="form-control" id="pass" placeholder="密码">
</div>
</form>
</div>
</body>
</html>
