title: custom attr selector using jquery
body: <pre><code>&lt;div id="placeholdSlots"&gt;
      &lt;div sort-helper="1"&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>How select the div using sort-helper custom attr? I know attr('sort-helper') can only get the value.</p>