jQuery set radio button

Your selector looks for the descendant of a input:radio[name=cols] element that has the id of newcol (well the value of that variable).

Try this instead (since you're selecting by ID anyway):

$('#' + newcol).prop('checked',true);

Here is a demo: http://jsfiddle.net/jasper/n8CdM/1/

Also, as of jQuery 1.6 the perferred method of altering a property is .prop(): http://api.jquery.com/prop

In your selector you seem to be attempting to fetch some nested element of your radio button with a given id. If you want to check a radio button, you should select this radio button in the selector and not something else:

$('input:radio[name="cols"]').attr('checked', 'checked');

This assumes that you have the following radio button in your markup:

<input type="radio" name="cols" value="1" />

If your radio button had an id:

<input type="radio" name="cols" value="1" id="myradio" />

you could directly use an id selector:

$('#myradio').attr('checked', 'checked');

I found the answer here:
https://web.archive.org/web/20160421163524/http://vijayt.com/Post/Set-RadioButton-value-using-jQuery

Basically, if you want to check one radio button, you MUST pass the value as an array:

$('input:radio[name=cols]').val(['Site']);
$('input:radio[name=rows]').val(['Site']);