The jQuery UI effects core extends the base class API to be able to animate between two different classes. The following methods are changed. They now accept three additional parameters: speed, easing (optional), and callback.
The switchClass method allows you to visually transition from one class to another. (This functionality is often described as 'animateClass'.)
For example:
$(elem).switchClass('currentClass','newClass',500,'easeOutBounce',function(){
console.log('transition is done!');
});