How to manipulate a xml file and save it to disk? - node.js

Question

I have two xml files with exactly same structure. The only difference is the inner text of the tags.
I want to replace the value in the first file with the corresponding value in the second file.
I have tried using the xml2json but the problem is it removed all the comments which I need in the final output.
So currently I am using xmldom.
I am able to manipulate the text but the changes are lost when I try to save the file to the disk.
var DOMParser = require("xmldom").DOMParser;
var serializer = new (require('xmldom')).XMLSerializer;
var fs = require('fs');
let firstXML = `<root>
<!--This is just a comment-->
<string name="one">SOMETHING</string>
</root>`
let secondXML = `<root>
<string name="one">ELSE</string>
</root>`
var firstDoc = new DOMParser().parseFromString(firstXML, "text/xml");
var secondDoc = new DOMParser().parseFromString(secondXML, "text/xml");
let elementsFirst = firstDoc.getElementsByTagName("string");
let elementsSecond = secondDoc.getElementsByTagName("string");
for(let i = 0; i < elementsFirst.length; ++i) {
let el = elementsFirst[i];
let name = el.getAttribute("name");
for(let j = 0; j < elementsSecond.length; ++j) {
if(name = elementsSecond[j].getAttribute("name")) {
el.firstChild.nodeValue = elementsSecond[j].firstChild.nodeValue;
break;
}
}
}
fs.writeFileSync("output.xml", serializer.serializeToString(firstDocs));
//Required output
`<root>
<!--This is just a comment-->
<string name="one">ELSE</string>
</root>`

Answer 1

Please don't ask me why, but if you replace this line
el.firstChild.nodeValue = elementsSecond[j].firstChild.nodeValue;
with this one
el.firstChild.data = elementsSecond[j].firstChild.nodeValue;
it will work as expected.
P.S. You have a typo in your if statement, you need ===, a single = will usually return true
Update: after finding the solution - I found out that it is duplicate of this one