check button is enable or disable using jquery

check button is enable or disable using jquery

 var disabled = $("#buttonNew").is(":disabled");

i am tried to check the button is enabled or disabled using above code but above code returns always false .

Code for disable the button:

 $('[id$=buttonNew]').attr('disabled', 'disabled');

Code for enable the button

 $('[id$=buttonDelete]').removeAttr('disabled');