<script type="text/javascript" src="/js/jquery.js"></script>
var $p = jQuery("p"), p = $p[0];
$p.append(jQuery.hasData(p)+" ");
jQuery.data(p, "testing", 123);
$p.append(jQuery.hasData(p)+" ");
jQuery.removeData(p, "testing");
$p.append(jQuery.hasData(p)+" ");