title: how to detect MathML tag support (<mfrac>,<mtable>) from javascript?
body: <p>I can detect MathML support with:</p>
  
  <pre><code>var e = document.createElement('div');
      e.innerHTML = '&lt;math&gt;&lt;/math&gt;';
      var mathMLSupported = e.firstChild &amp;&amp; "namespaceURI" in e.firstChild &amp;&amp; e.firstChild.namespaceURI == 'http://www.w3.org/1998/Math/MathML';
  </code></pre>
  
  <p>but how to detect support for <code>&lt;mfrac&gt;</code> and  <code>&lt;mtable&gt;</code>  ?</p>