jQuery addBack() Method

<!DOCTYPE html>
<html>
<head>
<title>add -  jQuery Example</title>
 <script type="text/javascript" src="http://code.jquery.com/jquery-2.1.4.min.js">
 </script>
<script type="text/javascript">
         $(document).ready(function(){         
           $( "#demo-paragraph-before-addback" ).find("p").css( "background","yellow" );
           $( "#demo-paragraph-after-addback" ).find("p").addBack().css( "background","yellow" );
          });
</script>
</head>	
<body>
<div id="demo-paragraph-before-addback" style="padding:9px;border:1px solid black;">
<h3>Before AddBack</h3>
This is Demo Div 
<p>Demo Paragraph.</p>
<p> Demo Paragraph.</p>
</div><br><br>

<div id="demo-paragraph-after-addback" style="padding:9px;border:1px solid black;">
<h3>After AddBack</h3>
This is Demo Div 
<p>Add Back.</p>
<p> Demo Paragraph.</p>
</div>
</body>
</html>