Why am I not able to untick this checkbox using JavaScript?

Question

My ASP code is as follows:

<asp:CheckBox ID="chk" runat="server" Checked="false"/>

And in my JavaScript:

document.getElementById('chk').checked = result.isUserSpecific;
    if (result.isUserSpecific === 'False') {
        document.getElementById('chkUserSpecific').checked = 'False';
    }

I'm currently able to tick the checkbox through JavaScript when the result is true but I can't seem to untick the box.

I've tried changing 'False' to 'false' and it appears that the result being returned is definitely False. Any pointers would be welcome.

Answer 1

You need to assign a boolean value to the checked property, not a string.

false or true not 'False' and not 'false' .

'false' and 'False' are both true values when coerced into a boolean.

Answer 2

ASP.NET ensures HTML id attributes are unique on its controls by prefixing them. What you're declaring as chk is being converted to something like c100_c100_chk before being added to your page.

The easiest way to support this would be to use document.querySelector() , passing in an attribute selector which matches the end of your element's ID:

document.querySelector('[id$="chk"]').checked = ...;

Furthermore, the string value 'False' is a truthy value and will evaluate to true . You need to set this to false , not 'False' :

document.getElementById('chkUserSpecific').checked = false;