enabledIndices

The enabledIndices() function returns a list containing the zero-based indices of the currently enabled tabs.

<div id="tabs">
    <ul>
        <li>One</li>
        <li>Two</li>
    </ul>
    <div>Tab Pane 1</div> 
    <div>Tab Pane 2</div>
</div>

<script type="text/javascript">
    $(function () {
        $("#tabs").shieldTabs();

        // prints [0, 1]
        console.log(
           $("#tabs").swidget("Tabs").enabledIndices()
        );
    });
</script>