title: How to judge whether there is a specific child(.haschild('#test[att="test"]')) with jQuery?
body: <pre><code>&lt;div id="target"&gt;
  &lt;div id="test" att="test"&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p><code>$('target').haschild('#test')</code> should be <code>true</code></p>
  
  <p><code>$('target').haschild('#test[att="test"]')</code> should be <code>true</code></p>
  
  <p><code>$('target').haschild('#no')</code> should be <code>false</code></p>
  
  <p>Only <code>$('target')</code> is available.</p>