title: how to get textContent of textarea after change?
body: <p>I have a <code>textarea</code> tag. I want to be able to get its <code>textContent</code> after <code>textContent</code> changed?</p>
  
  <pre><code>&lt;textarea id="xxx"&gt; sameple text &lt;/textarea&gt; // before
  &lt;textarea id="xxx"&gt; sameple text and new text &lt;/textarea&gt; // after
  </code></pre>
  
  <p>I want listen even when the <code>textarea</code>'s content has changed.</p>