title: jQuery how to constantly check if element is hidden/visible?
body: <p>I have a couple of HTML5 videos on my website (within a slider), they automatically cycle every x seconds (or when user clicks "next slide").</p>
  
  <p>I want to stop the videos that are actually invisible to user, any ideas how to achieve that?</p>
  
  <p>I was tryng to do something like that, but I guess there's "each" missing and it works after click instead all the time (ok, in fact it doesn't work because "this" is used wrong here I guess, but you get the point, sorry, I'm not a JS-guy at all :():</p>
  
  <pre><code>document.on('click', ".videojs:hidden", function(){
     alert('video hidden!');    
     jQuery(this).player.pause();
  });
  </code></pre>