Question

I am trying to disable a control on a page using javascript.. I am doing the following but not able to do it successfully.. anything I am missing, please point out..

       if (some condition) {        
        var textBoxTemp = document.getElementById('_ctl21_m_txtTemp');
        textBoxTemp.disabled = true;
        }

I got the element id by looking at the source of the page. In the source the id shows

_ctl21:m_txtTemp

I tried using both

_ctl21:m_txtTemp and _ctl21_m_txtTemp

in the second line of code above..

Answer 1

You can use jquery prop() to disable the textbox.

$("[id$=txtTemp]").prop("disabled", true); 

Note: prop() is only available after jquery 1.6. If you are using an earlier version, you can use attr() instead:

$("[id$=txtTemp]").attr("disabled", "disabled"); 

Edit:

Since ASP.NET tends to mangle the ID of a control, there are several different ways you can find the control on the page such as:

$('[id$=txtTemp]')
$('#<%= txtTemp.ClientID %>')

Edit:

Since you seem to think that your control could be in an iframe, I found this solution from the following stackoverflow question: how-can-i-access-iframe-elements-with-javascript

function iframeRef( frameRef ) {
    return frameRef.contentWindow ? frameRef.contentWindow.document : frameRef.contentDocument
}

var iframe = iframeRef( document.getElementById('iframeID') )

You will now be able to search the iframe content as if it was the document via:

iframe.getElementByID('<%= txtTemp.ClientID %>').disabled = true;