更改Bootstrap输入组的大小
通过在.input-group本身中添加.form-group-lg，input-group-sm，input-group-xs之类的相对形式大小调整类，来更改输入组的大小。
您可以尝试运行以下代码来更改Bootstrap中输入组的大小：
示例
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap Example</title>
<link rel = "stylesheet" href = "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src = "https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script>
<script src = "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div style = "padding: 100px 100px 10px;">
<form class = "bs-example bs-example-form" role = "form">
<div class = "input-group input-group-lg">
<span class = "input-group-addon">@</span>
<input type = "text" class = "form-control" placeholder = "Twitterhandle">
</div>
<br>
<div class = "input-group">
<span class = "input-group-addon">@</span>
<input type = "text" class = "form-control" placeholder = "Twitterhandle">
</div>
<br>
<div class = "input-group input-group-sm">
<span class = "input-group-addon">@</span>
<input type = "text" class = "form-control" placeholder = "Twitterhandle">
</div>
</form>
</body>
</html>