Read a legacy .xls in a few lines

Modern readers like ExcelJS only handle the newer .xlsx. SheetJS, the de-facto .xls reader, no longer publishes to npm. xls-reader is a small, focused, npm-published alternative for the common case — get the cell values out of a legacy .xls.

import { readFile } from "node:fs/promises";
import { readXls } from "xls-reader";

const workbook = readXls(await readFile("report.xls"));

for (const sheet of workbook.sheets) {
  for (const row of sheet.rows) {
    console.log(row); // ["BANCO X S/A", 1.1, 2024-04-02T00:00:00.000Z, ...]
  }
}

Convert an .xls to JSON

import { readFirstSheet } from "xls-reader";

const sheet = readFirstSheet(bytes);
const [header = [], ...body] = sheet?.rows ?? [];

const json = body.map((row) =>
  Object.fromEntries(header.map((key, i) => [String(key), row[i] ?? null])),
);

How it compares