title: jquery to add one cell without refreshing the page
body: <p>I want to add one cell in a section each time I click the add button. The page is updated without refreshing.
  The html code is:</p>
  
  <pre><code>&lt;section&gt;
    &lt;p class="cell"&gt;content&lt;/p&gt;
  &lt;/section&gt;
  &lt;button type="button" id="addCell"&gt;add&lt;/button&gt;
  </code></pre>
  
  <p>How should I implement the js?Thanks!</p>