title: Why does Firefox give a syntax error, class is a reserved identifier?
body: <p>Opening a file named index.html with the following code on Firefox 43 renders the following error:</p>
  
  <pre><code>    &lt;!DOCTYPE html&gt;
      &lt;html&gt;
      &lt;head&gt;
      &lt;meta charset="UTF-8"&gt;
      &lt;title&gt;&lt;/title&gt;
      &lt;script&gt;
      "use strict";
      class RangeIterator {}
      &lt;/script&gt;
      &lt;/head&gt;
      &lt;body&gt;
      &lt;/body&gt;
      &lt;/html&gt;
  </code></pre>
  
  <p>I see the following error in the console:</p>
  
  <pre><code>SyntaxError: class is a reserved identifier
  </code></pre>
  
  <p>Any idea why I'm getting that error?</p>