@imprentajs/xlsx

The Imprenta spreadsheet writer, as a native Node addon. Writes real XLSX, where a number stays a number.

npm i @imprentajs/xlsx@alpha

import { write } from '@imprentajs/xlsx';

const { xlsx, sheets, bytes } = await write(ir);

ir is a JSON string. The usual way to produce it is @imprentajs/react.

Why a separate package from the PDF side

A page and a sheet are not the same model, and pretending otherwise is how spreadsheets get ruined. In a PDF the engine decides what every glyph looks like; in a workbook it decides nothing — a cell carries a value and a type, and Excel renders it when somebody opens the file. Writing 1200 as text into a PDF gives you the characters. Writing it as text into a sheet makes SUM return zero, and the recipient gets a wrong total.

So this package shares the vocabulary with the PDF engine and none of the model.

• write(ir) → { xlsx, bytes, sheets }
• writeToFile(ir, path) — no Buffer ever exists; use it for anything large
• new Book(sheets, { path }) from @imprentajs/xlsx/stream — feed rows in

Sheets, columns and frozen panes are declared up front because the format names every sheet in its first entry. Rows are not, because a streaming producer does not have them yet. Merges can come last, which is what lets a total row's span be decided once the row count is known.

One writer, every runtime

The writer is a single WebAssembly module that imports nothing at all, so there is no per-platform package to install and nothing to pick at run time. The same file runs in Node, the browser, Deno, Bun and on an edge worker.

The calls above go to a worker. In a browser, reach for the writer directly:

import { Writer } from '@imprentajs/xlsx/writer';

const writer = await Writer.load({ wasm });
const { xlsx } = writer.write(ir);   // synchronous: put it in a Worker

The bytes come back as a Uint8Array rather than a Buffer, because Buffer is Node's. Buffer.from(xlsx) gets the string helpers back at no cost.

Status

Alpha. It works and is built test-first, but the API is not settled.

Apache-2.0 · github.com/imprenta-project/imprenta