xml to Xml

How to write a java script program to display XML file with tags on the other XML file
<header>
<title>c programming </title>
<author> Dennis </author>
<price> 200 </price>
</header>
to above XML the output should be also same
<header>
<title>c programming </title>
<author> Dennis </author>
<price> 200 </price>
</header>
and after that how to find or mark up the differences if exist even if on tags or content.