Getting selected value from RadioButtonList using JavaScript.

<script language = "javascript" type = "text/javascript">
    function Get_RadiobuttonList_SelectedValue() 
    {            
            var list = document.getElementById("<%= rdbtnLst.ClientID %>"); //Cleint ID of RadioButtonList
            var rdbtnLstValues = list.getElementsByTagName("input");
            var Checkdvalue;
            for (var i = 0; i < rdbtnLstValues.length; i++) 
            {
                if (rdbtnLstValues[i].checked) 
                {
                    Checkdvalue = rdbtnLstValues[i];
                    break;
                }
            }
            if (Checkdvalue) 
            {
                alert(Checkdvalue.value);
            }
        }
</script>
<div>
     <asp:RadioButtonList ID="rdbtnLst" AutoPostBack="true" runat="server" RepeatDirection="Horizontal">
         <asp:ListItem Selected="True">One</asp:ListItem>
         <asp:ListItem>Two</asp:ListItem>
         <asp:ListItem>Three</asp:ListItem>
         <asp:ListItem>Four</asp:ListItem>
        </asp:RadioButtonList>
      <asp:Button ID="Button1" runat="server" OnClientClick="GetSelectedValue()" Text="Button" />
</div>