How to test for a blank value in the ajax return value ?

How to test for a blank value in the ajax return value ?

Hello,

Im wanting to display a dialog box if a ajax return value isnt blank.

How do I compare to a blank value?

success: function($html){                    
if ($html !== "") {                          
 $("#msgarea").empty();                      
 $("#msgarea").append($html);                
 $("#msgarea").dialog({