请问邮箱表单验证是如何实现提示填写完整的？
<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>基础表单</title>
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
</head>
<body>
<form role="form">
<div>
<label for="exampleInputEmail1">邮箱：</label>
<input type="email" id="exampleInputEmail1" placeholder="请输入您的邮箱地址">
</div>
<div>
<label for="exampleInputPassword1">密码</label>
<input type="password" id="exampleInputPassword1" placeholder="请输入您的邮箱密码">
</div>
<div>
<label>
<input type="checkbox"> 记住密码
</label>
</div>
<button type="submit" class="btn btn-default">进入邮箱</button>
</form>
</body>
</html>
