title: Problem using elem.dataset with IE and JSFiddle
body: <p>In this JSFiddle I created on Chrome, I find that it's unable to work on IE (I'm using IE9). Any reason as to this: <a href="http://jsfiddle.net/ZSB67/" rel="noreferrer">http://jsfiddle.net/ZSB67/</a>.</p>
  
  <pre><code>var backImage = [
      "http://alm7.wikispaces.com/file/view/RedBackground.bmp/144018347/RedBackground.bmp",
      "http://www.time2man-up.com/wp-content/uploads/2011/07/black-background.jpg",
      "http://1.bp.blogspot.com/--GorNQoEUxg/TfWPyckVeMI/AAAAAAAAAHk/0208KqQf3ds/s1600/yellow_background.jpg",
      ""
      ];
  
  function changeBGImage(whichImage) {
      if (document.body) {
          document.body.style.background = "url(\"" + backImage[whichImage] + "\")";
      }
  }
  var buttons = document.querySelectorAll('.bg_swap'),
      button;
  
  for (var i = 0; i &lt; buttons.length; i++) {
      button = buttons[i];
      button.onclick = function() {
          changeBGImage(this.dataset.index);
      };
  }
  </code></pre>