title: Detect fullscreen mode
body: <p>Modern desktop version of IE 10 is always fullscreen.</p>
  
  <p>There is a <a href="https://dvcs.w3.org/hg/fullscreen/raw-file/tip/Overview.html" rel="noreferrer">living specification</a> for <code>:fullscreen</code> pseudo-class on W3</p>
  
  <p>But when I tried to detect fullscreen with jQuery version 1.9.x and 2.x:</p>
  
  <pre><code>$(document).is(":fullscreen") 
  </code></pre>
  
  <p>it threw this error:</p>
  
  <blockquote>
    <p>Syntax error, unrecognized expression: fullscreen</p>
  </blockquote>
  
  <h1>Questions:</h1>
  
  <ol>
  <li><p>Is it because jQuery doesn't recognize this standard yet or IE10?</p></li>
  <li><p>What is the <em>legacy</em> way of checking fullscreen mode? I am expecting following results:</p>
  
  <pre><code>function IsFullScreen() {
       /* Retrun TRUE */
       /* If UA exists in classic desktop and not in full screen  */
       /* Else return FALSE */
  }
  </code></pre></li>
  <li><p>Can we do it without browser sniffing?</p></li>
  </ol>