How to Read and Write Excel Files in Node.js with the SheetJS (xlsx) Library

Jun 24, 2025

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To read and write Excel files in Node.js, the most popular library is xlsx (from the SheetJS project). It supports .xlsx, .xls, and .csv formats and is easy to use.

✅ Step-by-Step Guide to Read & Write Excel Files in Node.js

📦 Step 1: Install the `xlsx` Package

Run the following command:

npm install xlsx

📘 Example: Writing to an Excel File

const XLSX = require('xlsx');

// Sample data
const data = [
  ["Name", "Age", "City"],
  ["John", 30, "New York"],
  ["Alice", 25, "London"],
  ["Bob", 35, "Paris"]
];

// Create a new workbook and worksheet
const worksheet = XLSX.utils.aoa_to_sheet(data);
const workbook = XLSX.utils.book_new();
XLSX.utils.book_append_sheet(workbook, worksheet, "Sheet1");

// Write to file
XLSX.writeFile(workbook, "output.xlsx");

console.log("Excel file written successfully!");

📘 Example: Reading from an Excel File

const XLSX = require('xlsx');

// Read the Excel file
const workbook = XLSX.readFile('output.xlsx');

// Get the first sheet
const sheetName = workbook.SheetNames[0];
const worksheet = workbook.Sheets[sheetName];

// Convert to JSON
const jsonData = XLSX.utils.sheet_to_json(worksheet);

console.log("Excel file data:");
console.log(jsonData);

🔁 Input/Output Summary

Action	Method
Read file	`XLSX.readFile(filename)`
Write file	`XLSX.writeFile(workbook, filename)`
Create sheet	`XLSX.utils.aoa_to_sheet(data)`
Convert to JSON	`XLSX.utils.sheet_to_json(sheet)`

📝 Notes

AOA (Array of Arrays): Best for simple table-like data.
sheet_to_json() gives you an array of objects for easy processing.

Absolutely! Here’s an explanation of where and why you might need to read and write Excel files in Node.js, followed by real-world use cases.

📌 Where Is Excel File Handling Required in Node.js?

Working with Excel files in a Node.js backend or application is useful when your system needs to:

✅ 1. Export Reports or Data to Excel

When users want to download reports, sales data, invoices, or analytics in Excel format.

Example:

A web dashboard that allows exporting user activity logs as .xlsx
An admin panel that exports inventory or orders

✅ 2. Read Uploaded Excel Files

When users upload Excel files containing data to be processed, imported, or validated.

Example:

HR uploads employee records in Excel
Accountants upload tax or ledger entries in .xlsx
Students upload answer sheets or marksheets

✅ 3. Data Migration

Reading old Excel files and importing them into a new system or database.

Example:

Migrating legacy data from Excel to MongoDB or MySQL
Uploading master data like product catalogs or customer lists

✅ 4. Automation and Scheduled Tasks

Scheduled scripts that read Excel templates, process them, and generate output.

Example:

Nightly script that reads a .xlsx report and emails a summary
Cron job that reads monthly sales targets from Excel and stores them in the database

✅ 5. Online Formatted Excel Generation

When users fill out a form and get a custom Excel report/download with formatting.

Example:

Loan EMI calculators generating .xlsx reports
Quotation generators for e-commerce or B2B services

💼 Real-World Use Cases

Use Case	Description
School Management System	Import student data, export mark sheets
E-commerce Admin Panel	Export order lists or product catalogs
Finance / Payroll App	Generate payslips, read salary structures
Inventory Management	Upload or download stock records
CRM Systems	Export contacts or leads