title: Why does forEach() not work in an iframe in IE11?
body: <p>This question was closed as off-topic, so I've <strong>marked</strong> the <em>missing</em> info.</p>
  
  <p><strong>Specific problem or error</strong> plus <strong>shortest code neccesary:</strong></p>
  
  <p>The code below doesn't work in IE11, if it's in an iframe of certain websites.
  ("Certain" is not specific, but I don't have a public demo. I can't make one, until I find the cause in my private code. Still, the question is specific enough to be answered by an expert, that's why I've asked SO instead of a long debugging process without any idea.)</p>
  
  <pre><code>['a', 'b'].forEach(function(elem){console.log(elem);});
  </code></pre>
  
  <p>The <a href="http://msdn.microsoft.com/en-us/library/ie/dn720784(v=vs.94).aspx" rel="noreferrer">error</a> says that the array doesn't support the forEach method.</p>
  
  <p><strong>Desired behavior:</strong></p>
  
  <blockquote>
    <p>The forEach() method executes a provided function once per array
    element. - <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach" rel="noreferrer">MDN</a></p>
  </blockquote>