var planList=document.all ('rblPlanType');
for(var i=1;i<planList.length;i++)
{
if(planList[i].checked)
{
var planType=planList[i].value;
}
}
<asp:RadioButtonList ID="rblPlanType" runat="server" RepeatDirection="Horizontal" >
<asp:ListItem Value ="周" Selected ="true" >周</asp:ListItem>
<asp:ListItem Value ="月" >月</asp:ListItem>
<asp:ListItem Value ="季">季</asp:ListItem>
<asp:ListItem Value ="年">年</asp:ListItem>
</asp:RadioButtonList></td>