var value= $("input:radio[name='per'][checked]").val();
$("input[name='testradio']:eq(1)").attr("checked","checked");//
eq(1)表示第二个
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang='zh-CN' xml:lang='zh-CN' xmlns='http://www.w3.org/1999/xhtml'>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<script type="text/javascript" src="http://www.oschina.net/js/2012/jquery-1.7.1.min.js"></script>
<script>
$(function(){
$("#btnGetRadioValue").click(function(){
var value=$("input:radio[name='per'][checked]").val();
alert(value);
});
$("#btnSetRadioValue").click(function(){
var value=$("input:radio[name='per'][checked]").val();
value=value*1-1;
if(value==0)
value=1;
else
value=0;
$("input:radio[name='per']:eq("+value+")").attr("checked","checked");
});
$("#btnGetSelectValue").click(function(){
var value=$("#ddl").val();
alert(value);
});
$("#btnSetSelectValue").click(function(){
var value=$("#ddl option:eq(2)").attr("selected","selected");
});
});
</script>
</head>
<body>
1<input type="radio" name="per" value="1"/>
2<input type="radio" name="per" value="2"/>
<input type="button" value="GetRadioValue" id="btnGetRadioValue"/>
<input type="button" value="SetRadioValue" id="btnSetRadioValue"/><br/>
<select id="ddl">
<option value="-1">--</option>
<option value="1">1</option>
<option value="2">2</option>
</select>
<input type="button" value="GetSelectValue" id="btnGetSelectValue"/>
<input type="button" value="SetSelectValue" id="btnSetSelectValue"/>
</body>
</html>