我有这个表格:
<form>
<div class="box">
<h1>Contact form :</h1>
<label>
<span>Typ: </span>
<input type="radio" name="typ" value="admin" />admin<br />
<input type="radio" name="typ" value="user" />user<br />
</label>
<label>
<span>E-mail :</span>
<input type="text" class="post" name="email" id="email"/>
</label>
<label>
<span>Subject :</span>
<input type="text" class="post" name="subject" id="subject"/>
</label>
<label>
<span>If admin :</span>
<input type="text" class="post" name="ifadmin" id="ifadmin"/>
</label>
</div>
</form>
如何做这样的事情:如果我选择第一个收音机“admin”使用jquery动态显示“ifadmin”,如果我选择“user”不显示?