Question

I have a text box whose value I need to set in javascript function.
I calculate no of checkboxes checked in a grid and then assign the value to a hidden field whose value in turn is assigned to a text box.
Following is JS function.

function CountChkBx_tpm() {
        var gvTrNomList = document.getElementById("gvTrNomList");
        var numChecked = document.getElementById("hdn2");
        var frm = document.forms['gvTrNomList'];
        var flag = false;
        for (var i = 0; i < document.forms[0].length; i++) {
            if (document.forms[0].elements[i].id.indexOf('IsTPMSelected') != -1) {
                if (document.forms[0].elements[i].checked) {
                    numChecked = numChecked + 1;
                }
            }
        }

        if (numChecked > 0)
            document.getElementById('<%=txtTPMRecom.ClientID %>').Value = numChecked;
        else
            document.getElementById('<%=txtTPMRecom.ClientID %>').Value = '0';
    }

It is being called at OnClick of checkboxes within grid:

<ItemTemplate>
                                <asp:CheckBox type="checkbox" runat="server" ID="IsTPMSelected" onclick="CountChkBx_tpm()" />
                            </ItemTemplate>

The same functionality is used for another checkbox with another JS function to set value for another textbox..and that is working absolutely fine!!
What could be the trouble!!

  function CountChkBx() {
        var gvTrNomList = document.getElementById("gvTrNomList");
        var numChecked = document.getElementById("hdn");
        var frm = document.forms['gvTrNomList'];
        var flag = false;
        for (var i = 0; i < document.forms[0].length; i++) {
            if (document.forms[0].elements[i].id.indexOf('IsPocSelected') != -1) {
                if (document.forms[0].elements[i].checked) {
                    numChecked = numChecked + 1;
                }
            }
        }

        if (numChecked > 0) {

            document.getElementById('<%=txtCounterConfirmation.ClientID %>').value = numChecked;

        }
        else {
            document.getElementById('<%=txtCounterConfirmation.ClientID %>').Value = '0';
        }
    }

this is for following check box

             <ItemTemplate>
                                <asp:CheckBox type="checkbox" runat="server" ID="IsPocSelected" onclick="CountChkBx()" />
                            </ItemTemplate>
                        </asp:TemplateField>

The text boxes are:

        <td style="width: 100px">
                            <asp:TextBox ID="txtCounterConfirmation" runat="server"></asp:TextBox>
                        </td>
                    </tr>
                    <tr>
                        </td>
                        <td style="width: 100px">
                            <asp:TextBox ID="txtTPMRecom" runat="server"></asp:TextBox>
                        </td>

Answer 1

As far as I think you need to use

document.getElementById('<%=txtTPMRecom.ClientID %>').value

Instead of

document.getElementById('<%=txtTPMRecom.ClientID %>').Value

Concluding javscript code

function CountChkBx_tpm() {
        var gvTrNomList = document.getElementById("gvTrNomList");
        var numChecked = document.getElementById("hdn2");
        var frm = document.forms['gvTrNomList'];
        var flag = false;
        for (var i = 0; i < document.forms[0].length; i++) {
            if (document.forms[0].elements[i].id.indexOf('IsTPMSelected') != -1) {
                if (document.forms[0].elements[i].checked) {
                    numChecked = numChecked + 1;
                }
            }
        }

        if (numChecked > 0)
            document.getElementById('<%=txtTPMRecom.ClientID %>').value = numChecked;
        else
            document.getElementById('<%=txtTPMRecom.ClientID %>').value = '0';
    }