title: ".addEventListener is not a function" why does this error occur?
body: <p>I’m getting an ".addEventListener is not a function" error. I am stuck on this:</p>
  
  <pre><code>var comment = document.getElementsByClassName("button");
  function showComment() {
    var place = document.getElementById('textfield');
    var commentBox = document.createElement('textarea');
    place.appendChild(commentBox);
  }
  comment.addEventListener('click', showComment, false);
  </code></pre>
  
  
  
  <pre><code>&lt;input type="button" class="button" value="1"&gt;
  &lt;input type="button" class="button" value="2"&gt;
  &lt;div id="textfield"&gt;
  &lt;/div&gt;
  </code></pre>