how to get a control name using javascript in asp.net page which uses a master page

To get a control name placed inside an asp.net page which uses a master page.

if (document.getElementById("<%=txtDtRecvd.ClientID %>").value == "") {

                alert("Please provide Received Date.");

                document.getElementById("<%=txtDtRecvd.ClientID %>").focus();

                return false;

            }

else

{
//
}