jQuery onclick toggle class name

Question

Using jQuery, how do I toggle classA to classB on click going from:

<a class="switch" href="#">Switch</a>
<div class="classA"></div>


$('.switch').on('click', function(e){
    $('.classA').removeClass('classA').addClass('classB');
    e.preventDefault();
};

How do I toggle the class, instead of just replacing it like I'm doing here?