title: Jquery on focus event delegation
body: <p>For some strange reason this simple function doesn't seem to work:</p>
  
  <pre><code>$("body").on("focus", this, function(){
      alert('d');
  })
  </code></pre>
  
  <p><code>this</code> is input or textarea element.</p>
  
  <p>If i were to do this:</p>
  
  <pre><code>$(this).on("focus", function(){
      alert('d');
  })
  </code></pre>
  
  <p>It would work on those elements that exists at the moment, but i event would not fire up on newly created elements, what am i doing wrong?</p>