is there any library that can give me
XPATH for all the nodes in HTML page
Yes, if this HTML page is a well-formed XML document.
Depending on what you understand by “node”…
//*
selects all the elements in the document.
/descendant-or-self::node()
selects all elements, text nodes, processing instructions, comment nodes, and the root node /.
//text()
selects all text nodes in the document.
//comment()
selects all comment nodes in the document.
//processing-instruction()
selects all processing instructions in the document.
//@*
selects all attribute nodes in the document.
//namespace::*
selects all namespace nodes in the document.
Finally, you can combine any of the above expressions using the union (|) operator.
Thus, I believe that the following expression really selects “all the nodes” of any XML document:
/descendant-or-self::node() | //@* | //namespace::*