title: target an element in another one by getElementById
body: <p>I have two element like this:</p>
  
  <pre><code>&lt;div id="first"&gt;
      &lt;div id="test"&gt;&lt;/div&gt;
  &lt;/div&gt;
  
  
  &lt;div id="second"&gt;
      &lt;div id="test"&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>then i want to getElementbyId('test'), However I need 'test' in first div.
  meanwhile this is an example and my div doesn't have pre-defined order.</p>