i want to break out each three items in a list and add a class to that child like;
<ul>
<li>1</li>
<li>2</li>
<li>3</li><!--target list item-->
<li>4</li>
<li>5</li>
<li>6</li><!--target list item-->
<li>7</li>
</ul>
任何想法?