Add Elements to XML file using nodejs

I have a XML file as

<main>
<iframe>
    <name>1234</name>
    <url1>123</url1>
    <url2>345</url2>
</iframe>
<iframe>
    <name>563466</name>
    <url1>345435</url1>
    <url2>3453</url2>
</iframe>
</main>

I need to insert following element inside main in the above xml file using nodejs

<iframe>
    <name>563466</name>
    <url1>345435</url1>
    <url2>3453</url2>
</iframe>

Am using elementtree module for creating xml file like as follows

var et = require('elementtree');
var XML = et.XML;
var ElementTree = et.ElementTree;
var element = et.Element;
var subElement = et.SubElement;
root = element('main');
root.set('xmlns', 'http://www.w3.org/2005/Atom');

iframeTag = subElement(root, 'iframe');

iframeTitle = subElement(iframeTag, 'title');
iframeTitle.text = title;

iframeUrl1 = subElement(iframeTag, 'url1');
iframeUrl1.text = url1;

iframeUrl2 = subElement(iframeTag, 'url2');
iframeUrl2.text = url2;

etree = new ElementTree(root);
xml = etree.write({'xml_declaration': false});

I can add elements by using elementtree module. But if I restart the server, root will be undefined. So I cant update elements in the above manner. Can anyone help me to resolve?

I found the solution,

var dataNew, etreeNew;
dataNew = fs.readFileSync('report.xml').toString();
etreeNew = et.parse(dataNew);

iframeTag = subElement(etreeNew._root, 'iframe');

iframeTitle = subElement(iframeTag, 'title');
iframeTitle.text = title;

iframeUrl1 = subElement(iframeTag, 'url1');
iframeUrl1.text = url1;

iframeUrl2 = subElement(iframeTag, 'url2');
iframeUrl2.text = url2;

etree = new ElementTree(etreeNew._root);
xml = etree.write({'xml_declaration': false});

For elementtree parsing