.attr('checked','checked') does not work

Question

I am trying to check radio. Neither the following works:

[edit]

$(\'selector\').attr(\'checked\',\'checked\');
$(\'selector\').attr(\'checked\',true)         


        

Answer 1

$('.checkbox').prop('checked',true); 
$('.checkbox').prop('checked',false);

... works perfectly with jquery1.9.1