How to get elements with class "a b" and change it to "a" only?
<pre><code>&lt;div class="a b"&gt;&lt;/div&gt;
</code></pre>

<p>Say, I want to change it to:</p>

<pre><code>&lt;div class="a"&gt;&lt;/div&gt;
</code></pre>

<p>And reversely, how to add class "b" to a <code>div</code> with class "a"?</p>
