title: How to select within a container with jQuery?
body: <pre><code>&lt;div id="container1"&gt;
  &lt;span&gt;...&lt;/span&gt;
  &lt;/div&gt;
  &lt;div id="container2"&gt;
  &lt;span&gt;...&lt;/span&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Say if I have get the jQuery object $('container1'),how to find the <code>&lt;span&gt;</code> in it?</p>