How to check if an element does NOT have a specific class?

if (!$(this).hasClass("test")) {

Select element (or group of elements) having class "abc", not having class "xyz":

    $('.abc:not(".xyz")')

When selecting regular CSS you can use .abc:not(.xyz).

sdleihssirhc's answer is of course the correct one for the case in the question, but just as a reference if you need to select elements that don't have a certain class, you can use the not selector:

// select all divs that don't have class test
$( 'div' ).not( ".test" );
$( 'div:not(.test)' );  // <-- alternative