 <p>That's because <code>switchClass</code> is not a function defined by the jQuery plugin. It is actually part of the <a href="http://api.jqueryui.com/switchclass/" rel="nofollow">jQuery UI framework</a>. However, if you need to "switch" classes using the jQuery plugin you can use either <code>toggleClass</code>, <code>removeClass</code> and <code>addClass</code>. Furthermore, you can even use <code>animate</code> to customise the transitions between property values</p>