How to Read CSV File in Node.js: Simple Guide with Example

To read a CSV file in Node.js, you can use the built-in fs module to read the file content and then parse it manually or use a library like csv-parser for easier parsing. The csv-parser library streams the file and converts each row into a JavaScript object automatically.

Syntax

Using the csv-parser library, the basic syntax involves creating a readable stream from the CSV file with fs.createReadStream(), then piping it to csv() which parses the CSV data row by row.

• fs.createReadStream('file.csv'): Opens the CSV file as a stream.
• csv(): Parses CSV data into JavaScript objects.
• .on('data', callback): Handles each parsed row.
• .on('end', callback): Runs after all rows are processed.

javascript

const fs = require('fs');
const csv = require('csv-parser');

fs.createReadStream('file.csv')
  .pipe(csv())
  .on('data', (row) => {
    console.log(row);
  })
  .on('end', () => {
    console.log('CSV file successfully processed');
  });

Example

This example reads a CSV file named data.csv with columns name and age. It prints each row as an object and shows a completion message.

javascript

const fs = require('fs');
const csv = require('csv-parser');

fs.createReadStream('data.csv')
  .pipe(csv())
  .on('data', (row) => {
    console.log(row);
  })
  .on('end', () => {
    console.log('CSV file successfully processed');
  });

Output

{"name":"Alice","age":"30"}
{"name":"Bob","age":"25"}
CSV file successfully processed

Common Pitfalls

Common mistakes when reading CSV files in Node.js include:

• Not installing or importing the csv-parser library before use.
• Trying to read large CSV files without streaming, which can cause memory issues.
• Assuming CSV columns are automatically typed; all values are strings unless converted.
• Not handling errors on the file stream or parser.

Always handle errors and use streaming for large files.

javascript

const fs = require('fs');
const csv = require('csv-parser');

// Wrong: reading entire file synchronously (bad for large files)
// const data = fs.readFileSync('data.csv', 'utf8');
// console.log(data);

// Right: streaming and parsing
fs.createReadStream('data.csv')
  .pipe(csv())
  .on('data', (row) => {
    console.log(row);
  })
  .on('error', (err) => {
    console.error('Error reading CSV:', err);
  })
  .on('end', () => {
    console.log('Done processing CSV');
  });

Quick Reference

Summary tips for reading CSV files in Node.js:

• Use fs.createReadStream() to read files efficiently.
• Use csv-parser for easy CSV parsing.
• Handle data, end, and error events.
• Convert string values to numbers or dates if needed.
• Install csv-parser with npm install csv-parser before use.

Key Takeaways

Use the csv-parser library with fs.createReadStream() to read CSV files efficiently in Node.js.

Always handle data, end, and error events when streaming CSV files.

CSV values are strings by default; convert types as needed after parsing.

Avoid reading large CSV files synchronously to prevent memory issues.

Install csv-parser via npm before using it in your project.