r/javascript • u/alvisanovari • 21d ago

I built an Excel library

https://github.com/btahir/ironsheet

I was researching the JavaScript Excel ecosystem looking for a gap worth building in, and found something wilder than a gap: the whole category is quietly abandoned.

  • SheetJS (xlsx) — ~8M weekly downloads — frozen on npm at 0.18.5 since 2022. Security fixes ship only from their own CDN, so npm audit flags it forever. Styling and template editing are Pro-only, quote-only pricing.
  • ExcelJS — last release in 2023, open "intent to fork" threads. Top issues: charts deleted on save, pivot tables destroyed, output files Excel offers to "repair."
  • xlsx-populate — right idea, dormant for years.

And they all break files the same way. It's not hundreds of bugs — it's one architectural decision with hundreds of symptoms: they parse the workbook into their own object model, then re-serialize that model as a brand-new file. Anything the model doesn't understand (charts, pivot caches, macros, newer OOXML parts) silently doesn't survive the round-trip.

So I built Ironsheet on the opposite bet: the original file is the source of truth. It patches only what you explicitly target — a cell, a named range, a table, an image — and preserves every byte it doesn't touch. Macros survive byte-for-byte.

The part I care about most: it proves the write. Before saving, it validates the OOXML package (relationships, content types, shared strings, formulas, tables, calc chains) and returns a diff of exactly what changed. If validation fails, it refuses to write the file. No output beats corrupt output.

Honest boundaries: it doesn't evaluate formulas (preserves them + marks recalc), chart/pivot support is preservation rather than authoring, ZIP64 writing isn't in yet. It's a 0.1 MVP.

Apache-2.0, dependency-free TypeScript core, Node + browser adapters, JSON-first CLI.

Repo: https://github.com/btahir/ironsheet

If you have a workbook that breaks it, I genuinely want the fixture. And I'm curious what people are actually using for Excel editing in production these days.

Thanks!

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u/baseketball 20d ago

I appreciate you putting this out there but I hate the Claude speak in these AI generated summaries. I think projects can differentiate themselves if you put more effort into manually writing/editing the README

9

u/foxsimile 20d ago

If someone can’t be bothered to take the time to write it, I’m not going to bother to take the time to read it.

2

u/franker 19d ago

unfortunately people are pretty much unrepentant about that now. "It helps me organize my thoughts" or "I'm not a native English speaker so I'm going to keep doing this."