add a class to every other three lines in jquery?
<pre><code>&lt;ul id="test"&gt;
&lt;li&gt;test&lt;/li&gt;
&lt;li&gt;test&lt;/li&gt;
&lt;li&gt;test&lt;/li&gt; // add a class to this li
&lt;li&gt;test&lt;/li&gt;
&lt;li&gt;test&lt;/li&gt;
&lt;li&gt;test&lt;/li&gt;  // add a class to this li
&lt;li&gt;test&lt;/li&gt;
&lt;li&gt;test&lt;/li&gt;
&lt;li&gt;test&lt;/li&gt; // add a class to this li
&lt;/ul&gt;
</code></pre>

<p>how to use jquery to add a class to the above li lines which i add a comment. thank you.</p>
