title: MutationObserver syntax error on IE 11
body: <p>I'm working with a MutationObserver to change the values of some variables when I switch the content of a panel (I'm useing Bootstrap tabs). Everything is working just fine in Chrome and Firefox, but for some reason, when I test it with IE, it shows a syntax error in the console and the script breaks. This is my MutationObserver code:</p>
  
  <pre><code>var observer = new MutationObserver(function (MutationRecords, MutationObserver) {
          dataTable = null;
          tabla = null;
          tabActiva = $('.tab-content').find('.active');
          formFiltro = tabActiva.find('form');
          tabla = tabActiva.find('table');
      });
  
      observer.observe(target, {
          childList: true,
          attributeFilter: ['class'],
          subtree: true
      });
  </code></pre>
  
  <p>Console points the error is on the observer.observe(). I don't know what's happening. Thanks in advance.</p>
  
  <p><a href="https://i.stack.imgur.com/EgPlT.png" rel="noreferrer"><img src="https://i.stack.imgur.com/EgPlT.png" alt="enter image description here"></a></p>
  
  <p>Just in case, this is my "target":</p>
  
  <pre><code>var target = $('.tab-content &gt; .tab-pane').get(0);
  </code></pre>