ASP.NET UserControl javascript is not loading HTML to its variable

Question

I have created UserControl that I wish to use on multiple pages. This control contains classic javascript but for some reason it will not load element to a variable. Client IDs look ok.

This is button that activates javascript:

<input type="submit" name="ctl00$ContentPlaceHolder1$ContactList$btn_NewContact" value="Potvrdit" onclick="javascript:return CheckContactName();" id="ContentPlaceHolder1_ContactList_btn_NewContact" class="MyButton" style="color:white;" />

This is the textbox:

<input name="ctl00$ContentPlaceHolder1$ContactList$con_fullname" type="text" id="ContentPlaceHolder1_ContactList_con_fullname" class="MyTextBox" />

This is Javascript function:

    function CheckContactName() {
    name = document.getElementById("ContentPlaceHolder1_ContactList_con_fullname");

    if (name.value == '' | name.value == null) {
        return false;
    }

    UploadContact();

    return true;
}

Now, when I debug this in a console the name.value is undefined. The name variable itself is just "[object HTMLInputElement]".

So no matter what is in that textbox, this function is always false. I also checked all IDs inside final client page and there are no duplicates. Can you tell why this is? Thanks.

try set your input type to button not submit. As submit in webforms application will do a postback, so this could be the issue of your problem. — SehaxX
– SehaxX, Commented Jul 26, 2018 at 8:16
Problem with that is that in my .aspx file I use button like this: <asp:Button ID="btn_NewContact" runat="server" Text="Potvrdit" CssClass="MyButton" style="color:white;" OnClientClick="javascript:return CheckContactName();" OnClick="btn_NewContact_Click"/> OnClientClick return false it should not do postback — Somachr
– Somachr, Commented Jul 26, 2018 at 8:21
ok... have you enabled viewstate on control. page or global on the project. — SehaxX
– SehaxX, Commented Jul 26, 2018 at 8:25
yes try it. on your control or directly on the textbox if it is an asp:textbox — SehaxX
– SehaxX, Commented Jul 26, 2018 at 8:30

Emiliano Montesdeoca · Accepted Answer · 2018-07-26 08:14:24Z

1

I supose you set the input's value in code behind right?

Anyways, you might try using document.querySelector, and it seems that your logical operator is wrong, you are using | instead of ||.

function CheckContactName() {
    let name = document.querySelector(
        '#ContentPlaceHolder1_ContactList_con_fullname'
    );

    if ((name.value == '') || (name.value == null) || (name == undefined)) {
        return false;
    }

    UploadContact();

    return true;
}

answered Jul 26, 2018 at 8:14

Emiliano Montesdeoca

3841 silver badge9 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Somachr Over a year ago

No I do not set value in code behind and "|" will just try first expression first if it is false it will not care for the other one. I will look into querySelector.

Emiliano Montesdeoca Over a year ago

Does that work in Javascript tho? As far as I know in C# it does but never tested it on Javascript.

Somachr Over a year ago

Still, value is undefined either way

Somachr · Accepted Answer · 2018-07-26 09:08:54Z

1

Changed name to cname.

It seems that when you use control on a page that already contains some JavaScript function and that function declares variable with the same name as the one in usercontrol - this happends.

answered Jul 26, 2018 at 9:08

Somachr

4641 gold badge9 silver badges21 bronze badges

1 Comment

Somachr Over a year ago

But how to avoid it?

Collectives™ on Stack Overflow

ASP.NET UserControl javascript is not loading HTML to its variable

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related