JavaScript Postback on condition

Question

I need help with the javascript below please. I have 2 text boxes and 1 button on my form. What I would like to happen is if User enters a value in textbox one and not textbox two, then event need not be fired. However, if there is a value in textbox one and then textbox 2 then I want a post back to fire. My code below does not seem to be doing this at all and I would appreciate it if someone could help me fix this or better still figure it out. Thanks in advance

function Changed(textControl) {
    //  alert(textControl.value);
    var conlength = document.getElementById('<%=txtLength.ClientID %>');
    var conwidth = document.getElementById('<%=txtwidth.ClientID %>');
    if (conlength != null && conwidth != null) {
        if (conlength.value != null && conlength.value != ' ' && conwidth.value != null && conwidth.value != ' ') {
            // ' ' corresponds to c#'s String.Empty                
            __doPostBack(document.getElementById('<%=btncalcboardfeet.ClientID %>'), 'Calculate Board Feet Button event has been fired');
        }
    }
}

Answer 1

Why not take a simpler approach ... if your condition is met, programmatically click your submit button ;-) it's super simple using something like jquery even if you're into that sort of thing:

$("#<%=btncalcboardfeet.ClientID %>").click();

That way you don't have to try to figure out what internal javascript function asp.net is trying to call (as that may change in the future (however unlikely)).

edit: non jQuery version:

document.getElementById("<%=btncalcboardfeet.ClientID %>").click();

Answer 2

instead of that last if statement just try the following:

if (conlength.value && conwidth.value) {
            // ' ' corresponds to c#'s String.Empty                
            __doPostBack(document.getElementById('<%=btncalcboardfeet.ClientID %>'), 'Calculate Board Feet Button event has been fired');
}

Answer 3

If you are using ASP.NET WebForms and are using the asp:TextBox to collect the information, you can use the RequiredFieldValidator to ensure that both fields have a value before the page will postback.

Answer 4

You need to look at the length of the VALUE, not the element itself:

var conlength = document.getElementById('<%=txtLength.ClientID %>').value;