javascript - How to add/modify a node in XML file using node js -

let's have following xml code

<?xml version="1.0" encoding="utf-8" standalone="yes"?> <catalog>  <person>     <name>john</name>     <surname>smith</surname>  </person>  <person>     <name>abe</name>     <surname>lincoln</surname>   </person>   <person>     <name>james</name>     <surname>bond</surname>   </person> </catalog> 

and want add new node, let's following:

     <person>         <name>tony</name>         <surname>stark</surname>      </person> 

how do in node js? mean have file (/routes/index.js in node js express, exact), , want able add/modify existing xml file. i've tried fs.writefile(), writes whole new file, , fs.appendfile() adds header(?xml + encoding , stuff) , root nodes after last node, can't insert catalog node. can't rid of xml declaration header either.
i've been using .builder() this, , looked

router.post('/addnode', function(req,res) {  var obj = {name: "tony", surname: "stark"}; var fs = require('fs'); var xml2js = require('xml2js');  var builder = new xml2js.builder(); var xml = builder.buildobject(obj);    fs.writefile('public/test.xml', xml, function (err) if (err) throw err;     console.log('it\'s saved!'); });  }); 

finally want data from addnode, won't create var obj in function.

unless files' sizes unacceptable , cannot read them whole, can use xml2js , never work xml.

by using it, can read file, convert in object far easier manipulate, add stuff there , convert xml , write result again on original file.

looking @ example, create new object , append the file. instead, should read existent data , modify them, write (do not append them) file. that, have use parser object xml2js.