title: Get all visible CKEditor instances
body: <p>It is possible to loop through all the CKEditor instances like:</p>
  
  <pre><code>for(var instanceName in CKEDITOR.instances) {
    ...
  }
  </code></pre>
  
  <p>Some of the CKEditors are hidden in my case. So, how is it possible to loop through the visible CKEditors?</p>