ExcelTS

Read and write Excel files. TypeScript, minimal dependencies, works in Bun and browsers.

Why?

ExcelJS is great but carries Node.js baggage. ExcelTS is a modernized fork:

	ExcelJS	ExcelTS
Runtime	Node.js	Bun / Browser
Modules	CJS + ESM	ESM only
ZIP handling	3 packages (170KB)	fflate (8KB)
Bundle size	2.1 MB	289 KB
Node polyfills	Required	None
Types	Separate .d.ts	Native TypeScript

Browser-native: Uses Uint8Array, TextEncoder/TextDecoder, and Web Crypto APIs. No Buffer polyfill needed.

Install

bun add excelts

Examples

Write a spreadsheet

import ExcelTS from 'excelts';

const workbook = new ExcelTS.Workbook();
const sheet = workbook.addWorksheet('Sales');

sheet.columns = [
  { header: 'Product', key: 'product', width: 20 },
  { header: 'Revenue', key: 'revenue', width: 15 },
];

sheet.addRow({ product: 'Widget', revenue: 1500 });
sheet.addRow({ product: 'Gadget', revenue: 2300 });

sheet.getRow(1).font = { bold: true };

await workbook.xlsx.writeFile('sales.xlsx');

Read a spreadsheet

const workbook = new ExcelTS.Workbook();
await workbook.xlsx.readFile('sales.xlsx');

const sheet = workbook.getWorksheet('Sales');
sheet.eachRow((row, num) => {
  console.log(num, row.values);
});

Browser: Load from ArrayBuffer

<script src="excelts.min.js"></script>
<script>
async function loadExcel(arrayBuffer) {
  const workbook = new ExcelTS.Workbook();
  await workbook.xlsx.load(arrayBuffer);
  
  workbook.eachSheet((sheet) => {
    console.log(sheet.name);
    sheet.eachRow((row) => {
      console.log(row.values);
    });
  });
}

// From fetch
const response = await fetch('data.xlsx');
const buffer = await response.arrayBuffer();
await loadExcel(buffer);

// From file input
input.addEventListener('change', async (e) => {
  const file = e.target.files[0];
  const buffer = await file.arrayBuffer();
  await loadExcel(buffer);
});

// From drag & drop
dropzone.addEventListener('drop', async (e) => {
  const file = e.dataTransfer.files[0];
  const buffer = await file.arrayBuffer();
  await loadExcel(buffer);
});
</script>

Browser: Generate and download

const workbook = new ExcelTS.Workbook();
const sheet = workbook.addWorksheet('Export');

sheet.addRow(['Name', 'Email', 'Date']);
sheet.addRow(['John', 'john@example.com', new Date()]);

// One-liner download
await workbook.xlsx.download('export.xlsx');

// Or get Blob for custom handling (uploads, etc.)
const blob = await workbook.xlsx.writeBlob();

Stream large files

// Write 1M rows without memory issues
const writer = new ExcelTS.stream.xlsx.WorkbookWriter({ filename: 'big.xlsx' });
const sheet = writer.addWorksheet('Data');

for (let i = 0; i < 1_000_000; i++) {
  sheet.addRow([i, `Row ${i}`]).commit();
}
await writer.commit();

// Read large files
const reader = new ExcelTS.stream.xlsx.WorkbookReader('big.xlsx');
for await (const sheet of reader) {
  for await (const row of sheet) {
    // Process row
  }
}

Cell formatting

const cell = sheet.getCell('A1');

cell.value = 1234.56;
cell.numFmt = '$#,##0.00';
cell.font = { bold: true, color: { argb: 'FF0000' } };
cell.fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: 'FFFF00' } };
cell.border = { top: { style: 'thin' }, bottom: { style: 'thin' } };

Formulas

sheet.getCell('A1').value = 10;
sheet.getCell('A2').value = 20;
sheet.getCell('A3').value = { formula: 'SUM(A1:A2)' };

Images

const imageId = workbook.addImage({
  filename: 'logo.png',
  extension: 'png',
});

sheet.addImage(imageId, 'B2:D6');

Browser Build

The browser build (dist/excelts.min.js) uses only native browser APIs:

• Uint8Array instead of Node.js Buffer
• TextEncoder / TextDecoder for string encoding
• crypto.randomUUID() and crypto.getRandomValues() for crypto
• fflate for ZIP compression (pure JS, no WASM)

No polyfills required. Works in all modern browsers.

API

Full API matches ExcelJS. Key classes:

• Workbook - Container for worksheets
• Worksheet - Grid of cells, rows, columns
• Row / Cell - Data and formatting
• WorkbookWriter / WorkbookReader - Streaming API

License

MIT

Fork of ExcelJS by Guyon Roche.