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 ="http://www.mamicode.com/周"   Selected ="true" >周</asp:ListItem>
                    <asp:ListItem Value ="http://www.mamicode.com/月"  >月</asp:ListItem>
                    <asp:ListItem Value ="http://www.mamicode.com/季">季</asp:ListItem>
                   
                    <asp:ListItem Value ="http://www.mamicode.com/年">年</asp:ListItem>
                    </asp:RadioButtonList></td>

[转载]js 获取ASP RadioButtonList 选中的值