How do I find ID of an element by it's classname?
<p>How can I find the ID of the element that has the class <code>active</code>?</p>

<pre><code>&lt;a id='1' &gt;A&lt;/a&gt;
&lt;a id='2' &gt;B&lt;/a&gt;
&lt;a id='3' class='active'&gt;C&lt;/a&gt;
&lt;a id='4' &gt;D&lt;/a&gt;
&lt;a id='5' &gt;E&lt;/a&gt;
&lt;a id='6' &gt;F&lt;/a&gt;
</code></pre>
