Node.js: How to Convert CSV to JSON

Overview

Learn how to effortlessly transform CSV data into JSON format using Node.js, utilizing modern JavaScript syntax and libraries to streamline the process.

Before diving into the code examples, ensure you have Node.js installed. Basic knowledge of npm, asynchronous programming in JavaScript, and handling filesystems with Node.js is also recommended.

Basic Conversion

Understand the simplest method for CSV to JSON conversion using core Node.js modules.

const fs = require('fs');
const { parse } = require('csv-parse/sync');

const csvData = fs.readFileSync('data.csv', 'utf8');
const jsonData = parse(csvData, { columns: true, skip_empty_lines: true });
console.log(jsonData);

Streaming Data

A guide to converting large CSV files into JSON format using Node.js streams, to handle data efficiently and effectively.

const fs = require('fs');
const { parse } = require('csv-parse');
const { Transform } = require('stream');

const inputStream = fs.createReadStream('largeData.csv', 'utf8');
const outputStream = fs.createWriteStream('output.json');
const jsonTransform = new Transform({
  writableObjectMode: true,
  transform(chunk, encoding, callback) {
    // Transform CSV to JSON here
    this.push(JSON.stringify(chunk));
    callback();
  },
});

inputStream
  .pipe(parse({ columns: true }))
  .pipe(jsonTransform)
  .pipe(outputStream);

Using Third-Party Libraries

Explore using popular npm packages for an efficient and powerful CSV to JSON conversion process.

import fs from 'fs';
import csvtojson from 'csvtojson';

const readStream = fs.createReadStream('data.csv');
const writeStream = fs.createWriteStream('data.json');

readStream.pipe(csvtojson()).pipe(writeStream);

Advanced Parsing

Delve into advanced parsing techniques, including custom value transformations and error handling for robust CSV to JSON conversion.

import { pipeline } from 'stream';
import through2 from 'through2';
import csvtojson from 'csvtojson';

pipeline(
  fs.createReadStream('data.csv'),
  csvtojson().on('error', handleError),
  through2.obj(function (chunk, enc, callback) {
    // Perform any data transformation here
    callback(null, transformChunk(chunk));
  }),
  fs.createWriteStream('data.json'),
  (err) => {
    if (err) console.log('Pipeline failed.', err);
    else console.log('Pipeline succeeded.');
  }
);

function transformChunk(chunk) {
  // Define transformations here
  return chunk;
}

function handleError(error) {
  // error handling process
}

Asynchronous Conversion

Discover how to leverage async/await for converting CSV files to JSON asynchronously, enhancing performance and coding experience.

import fsPromises from 'fs/promises';
import parseAsync from 'csv-parse/lib/es5/sync';

async function convertCsvToJson(filePath) {
  const csvData = await fsPromises.readFile(filePath, 'utf8');
  return parseAsync(csvData, {
    columns: true,
    skip_empty_lines: true,
  });
}

convertCsvToJson('data.csv')
  .then((jsonData) => console.log(jsonData))
  .catch((error) => console.error(error));

Conclusion

In this tutorial, we explored a range of techniques for converting CSV files to JSON in Node.js, using both native modules and third-party libraries. Ensure that you select the method best suited to the size of your dataset and the complexity of your data transformation needs.