Create copies of template XLSM file using NodeJS? - node.js

Question

I have a node project where I need node to create a new XLSM file using an existing XLSM file as a template. The template contains a great deal of styling, images, and VBA. The application simply inserts values into a few cells and saves the new file with a discreet name.
I have tried XLSX and ExcelJS npms to accomplish this. Both fail in different ways:
ExcelJS: Doesn't seem to support writing XLSM files at this time. Attempting to do so results in a corrupt file.
XLSX: I've not been able to create a true copy of the template. It's missing formatting and VBA, among other things. This is the very basic code I'm starting with:
const templatePath = "C:/Users/rapsputinforever/Desktop/template.xlsm"
const directory = "C:/Users/rapsputinforever/Desktop"
const workbook = XLSX.readFile(templatePath);
// will insert data to some cells here
XLSX.writeFile(workbook, directory + '/copy.xlsm');
I know this package has a variety of options which don't seem related to the issue I'm having and helpful toward accomplishing what seems, on the surface, a very simple task:
Read Template
Add Values to Cells
Write as New File keeping all VBA, styling, and et cetera
I'm willing to look into other packages, libraries, even other technologies. This tool is part of the back-end of a React app, however I'm not sure React can accomplish this. I'm open to any advice. I appreciate the help!

Answer 1

I successfully accomplished the issue by breaking the problem down to its constituent parts. Knowing about the nature of excel files, that they are zipped packages of XML files (source here) then it's a matter of step-wise doing the following steps:
Create a duplicate of the template XLSM file, copy has ".zip" as extension ('fs')
Un-package the zip file ('extract-zip')
read sharedStrings.XML ('fs')
Count the number of iterations of XML tag " < s i > " in sharedStrings
Example:
let stringCount = (sharedStrings.match(/<si>/g) || []).length;
read worksheet1.XML (or whatever sheet data is to be inserted)
Locate the cell by finding the tag for it. If empty the tag will resemble this:
Example:
<c r="D10" s="29"/>
Note, r = cell address, s = style tag, you want to maintain both in the next step...
Replace the empty cell tag with the shared string flag and the desired index of the new string to be inserted.
Example:
<c r="D9" s="29" t="s"><v>${stringCount}</v></c>
To summarize so far, we replace the cell XML tag with the insert string which is inserted into the sharedStrings file and referenced by the index/count of that new string. This can be interated in a loop to insert an array of values to be inserted.
Save both sharedFiles.XML and worksheet1.XML ('fs')
Package the un-zipped folder into a new archive ('archiver')
Re-name the archived folder with '.XLSM' extention ('fs')
Cleanup, kill any duplicate zip files/folders
If the work-up is correct, the sharedString index is accurate, if the style ID is maintained, and the correct script structure applied with all these asynchronous actions, the resulting file should have the desired results because the integrity of the containing VBA, Styles, Queries, Images, etc, was all maintained by creating a true copy and manipulating that copy's constituent parts.
I am a novice developer, no doubt my approach is overly lengthy and inefficient, and my understanding of why this works versus these other libraries don't rests solely upon my intuition. I believe the issue is that ExcelJS and other NPMs create a worksheet "in the buffer" which unfortunately only contains any element of the original file that that library accounts for based on XLSX files. If ExcelJS isn't looking at VBA then the new worksheet won't have VBA because when that sheet was duplicated in the buffer it only duplicated anything within its scope.
I am still very much open to more suggestions/alternatives/approaches/wisdom. I hope to fine-tune this further to be scalable: I only was able to design this for my very specific application. If I do manage to generalize this and clean up my code I will share the snippet here.
Thanks,
EDIT: Hello! As it turns out, things are not so simple! Despite not prompting errors on opening the file, the duplicate still has some background issues which is made evident if you happen to utilize Power Query to parse though said XLSM files. Additionally, any formula that references the cells filled by the node solution will not be updated on opening the file. To solve this, run this VBA:
Application.CalculateFullRebuild
This will update all formulae on every sheet. Once this file is saved the sheet should be "normal" again. The issue at hand is based on the XML file calcChain.XML.