First I alert this, and alert 'undefined':
alert($("input[name='searchManagers']:checked").val());
But when I try this, why alert 'no':
if($("input[name='searchManagers']:checked").val() == 'undefined')
    alert('yes')
else
    alert('no')
That fix my problem:
if(typeof $("input[name='searchManagers']:checked").val() == 'undefined')
    alert('yes')
else
    alert('no')
 
     
     
     
     
     
    