Working with Excel in JavaScript (Node.js): Libraries and Code Examples

Working with Excel in JavaScript (Node.js): Overview of Libraries and Code Examples

Despite PythonLib being dedicated to the Python language, working with Excel spreadsheets is often required in the Node.js environment as well. JavaScript (especially on the server side) is actively used for report automation, data import from CRM systems, and price list generation. In this article, we will review three main libraries for working with Excel in Node.js, their capabilities, and provide practical code examples.

Why Node.js for Excel?

Node.js is an ideal choice for microservices and scripts that process large volumes of data. Excel libraries allow you to:

• Read existing .xlsx and .xls files.
• Create new spreadsheets from scratch.
• Format cells (colors, fonts, borders).
• Work with formulas, styles, and merged cells.
• Export data to CSV.

Top 3 Libraries for Excel in Node.js

1. ExcelJS — The Most Feature-Rich

ExcelJS is a powerful library with full support for the xlsx format. It allows working with streams, which is critical for large files. Supports styles, conditional formatting, charts, and sheet protection.

Installation:

npm install exceljs

Example 1: Reading an Existing File

const ExcelJS = require('exceljs');

async function readExcel(filePath) {  const workbook = new ExcelJS.Workbook();  await workbook.xlsx.readFile(filePath);    const worksheet = workbook.getWorksheet(1); // First sheet  worksheet.eachRow((row, rowNumber) => {    console.log(`Row ${rowNumber}: ${row.values.join(', ')}`);  });}

readExcel('data.xlsx');

Example 2: Creating a File with Formatting

const ExcelJS = require('exceljs');

async function createStyledExcel() {  const workbook = new ExcelJS.Workbook();  const sheet = workbook.addWorksheet('Report');    // Header with bold font and fill  const headerRow = sheet.getRow(1);  headerRow.values = ['Name', 'Age', 'City'];  headerRow.font = { bold: true, size: 12 };  headerRow.fill = {    type: 'pattern',    pattern: 'solid',    fgColor: { argb: 'FFFF00' } // Yellow background  };    // Data  sheet.addRow(['Anna', 28, 'Moscow']);  sheet.addRow(['Ivan', 35, 'Saint Petersburg']);    // Column widths  sheet.getColumn(1).width = 15;  sheet.getColumn(2).width = 10;    await workbook.xlsx.writeFile('output.xlsx');  console.log('File created!');}

createStyledExcel();

2. xlsx (SheetJS) — Lightweight and Fast

The xlsx library (also known as SheetJS) is a workhorse for simple operations. It does not support advanced formatting but handles reading/writing data well. Supports xlsx, xls, csv, ods formats.

Installation:

npm install xlsx

Example 3: Reading and Converting to JSON

const XLSX = require('xlsx');

function readToJSON(filePath) {  const workbook = XLSX.readFile(filePath);  const sheetName = workbook.SheetNames[0];  const sheet = workbook.Sheets[sheetName];    // Convert sheet to an array of objects  const data = XLSX.utils.sheet_to_json(sheet);  console.log(data);}

readToJSON('data.xlsx');

Example 4: Writing an Array of Data

const XLSX = require('xlsx');

function writeFromArray() {  const data = [    { Name: 'Olga', Age: 30, City: 'Kazan' },    { Name: 'Pyotr', Age: 42, City: 'Yekaterinburg' }  ];    const worksheet = XLSX.utils.json_to_sheet(data);  const workbook = XLSX.utils.book_new();  XLSX.utils