Add one xml element into another xml

Add one xml element into another xml

Please let me know how to do the following thing.
XML Document 1 :
<tag1 id="id1" name="myname">
<tag_child1 child1id="child1"></tag_child1>
</tag1>
XML Document 2 :
<tag_child2>
<tagchild2_child3 child_childid = "child_child3"> </tagchild2_child3>
</tag_child2>
Final Document :
<tag1 id="id1" name="myname">
<tag_child1 child1id="child1"></tag_child1>
<!-- Document 2 -->
<tag_child2>
<tagchild2_child3 child_childid = "child_child3">
</tagchild2_child3>
</tag_child2>
</tag1>
I tried using appendChild() function in javascript.But I wasn't able to do
it. Please help. Thanks