Question

// text Box
        &nbsp;&nbsp;<asp:TextBox ID="TextBox3"  runat="server" BackColor="Silver" 
            BorderColor="Silver" ontextchanged="TextBox3_TextChanged" 
            style="margin-left: 6px" Width="154px"></asp:TextBox>

// Submit button
        &nbsp;<asp:Button ID="Button6" runat="server" BackColor="Silver" 
            onClientclick='store_memID()' style="margin-left: 20px" Text="Submit" 
            Width="102px" Font-Bold="True" Height="28px" />


    <script type = "text/javascript">
        // Function to caputure client-input- Member_ID.
        function store_memID() {

            var mem_ID = document.getElementById('TextBox3').value;


            return confirm('TimeLine is displayed for: ' + mem_ID);
        }

    </script>

When I run the code and enter a value into the text box and then press the submit button:-
“Microsoft JScript runtime error: Unable to get value of the property ‘value’: object is null or undefined”.

Else, if I remove the ‘.value’ :-

<script type = "text/javascript">
    // Function to caputure client-input- Member_ID.
    function store_memID() {

        var mem_ID = document.getElementById('TextBox3');


        return confirm('TimeLine is displayed for: ' + mem_ID);
    }

</script>

and then run the program, enter value in text box and press submit then i get :-

“TimeLine is displayed for: Null”

I have been looking into solving this problem. not sure whats going wrong…

Edit (fix):- Server Side ID for my text box is ‘TextBox3’ but this doesn’t necessarily match up with the client side ID.
to get Client Side ID:- ‘<%=TextBox3.ClientID%>’

Answer 1

It’s been a while since I wrote asp forms but it is likely that the id on the client side (in your browser) is not what you think it is. This is/was one of the major pitfalls of web forms in my mind (This may have been made simpler in version 4.0, you’ll have to check that). You could use a css class (and use jQuery or similar to find your element) or inject the client side id into the java script e.g.;

<script type = "text/javascript">
    // Function to caputure client-input- Member_ID.
    function store_memID() {
        var mem_ID = document.getElementById('<%=TextBox3.ClientID%>').value;
        return confirm('TimeLine is displayed for: ' + mem_ID);
    }
</script>

UPDATE: fixed case error in ClientID as pointed out in comments