话不多说，请看代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title> new document </title>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
<link rel="stylesheet" type="text/css" href="" />
<style type="text/css"></style>
<script type="text/javascript" src="jquery-3.0.0.js"></script>
</head>
<body>
<input type="radio" name="radio" value="1" />1<br/>
<input type="radio" name="radio" value="2" />2<br/>
<input type="radio" name="radio" value="3" />3<br/>
<input type="radio" name="radio" value="4" />
<script type="text/javascript">
var a = $("input[name='radio']:checked").val();
alert("选中的radio的值是：" + a);
</script>
</body>
</html>