Classie Back
Classie.js is an awesome mega lightweight script that allows you to add, remove, toggle, and check for classes in the DOM very easily.
classie.has( element, 'my-class' ) // returns true/false
classie.add( element, 'my-new-class' ) // add new class
classie.remove( element, 'my-unwanted-class' ) // remove class
classie.toggle( element, 'my-class' ) // toggle class
<script src="js/classie.js"></script>