CSVtoJSON

Convert CSV files to JSON with no dependencies. Supports Node.js (Sync & Async), and Browser environments with full RFC 4180 compliance. Memory-efficient streaming for processing large files without loading them entirely into memory. See the Demo.

Overview

Transform CSV data into JSON with a simple, chainable API. Choose your implementation style:

• Synchronous API - Blocking operations for simple workflows
• Asynchronous API - Promise-based for modern async/await patterns with memory-efficient streaming for large files
• Browser API - Client-side CSV parsing for web applications

Demo and JSDoc

• Demo
• JSDoc

Features

✅ RFC 4180 Compliant - Proper handling of quoted fields, delimiters, newlines, and escape sequences
✅ Zero Dependencies - No external packages required
✅ Full TypeScript Support - Included type definitions for all APIs
✅ Flexible Configuration - Custom delimiters, encoding, trimming, and more
✅ Method Chaining - Fluent API for readable code
✅ Memory-Efficient Streaming - Process large files without loading them entirely into memory
✅ Comprehensive Error Handling - Detailed, actionable error messages with solutions (see ERROR_HANDLING.md)

RFC 4180 Standard

RFC 4180 is the IETF standard specification for CSV (Comma-Separated Values) files. This library is fully compliant with RFC 4180, ensuring proper handling of:

RFC 4180 Example

firstName,lastName,email
"Smith, John",Smith,john@example.com
Jane,Doe,jane@example.com
"Cooper, Andy",Cooper,andy@company.com

Note the quoted fields containing commas are properly handled. See RFC4180_MIGRATION_GUIDE.md for breaking changes and migration details.

Quick Start

Installation

npm install convert-csv-to-json

Synchronous (Simple)

const csvToJson = require('convert-csv-to-json');
const json = csvToJson.getJsonFromCsv('input.csv');

Asynchronous (Modern)

const csvToJson = require('convert-csv-to-json');
const json = await csvToJson.getJsonFromCsvAsync('input.csv');

Browser

const convert = require('convert-csv-to-json');
const json = await convert.browser.parseFile(file);

Documentation

Common Tasks

Parse CSV String

const json = csvToJson.csvStringToJson('name,age\nAlice,30');

Custom Delimiter

const json = csvToJson
  .fieldDelimiter(';')
  .getJsonFromCsv('input.csv');

Format Values

const json = csvToJson
  .formatValueByType()
  .getJsonFromCsv('input.csv');
// Converts "30" → 30, "true" → true, etc.

Handle Quoted Fields

const json = csvToJson
  .supportQuotedField(true)
  .getJsonFromCsv('input.csv');

Batch Process Files (Async)

const files = ['file1.csv', 'file2.csv', 'file3.csv'];
const results = await Promise.all(
  files.map(f => csvToJson.getJsonFromCsvAsync(f))
);

Configuration Options

All APIs (Sync, Async and Browser) support the same configuration methods:

• fieldDelimiter(char) - Set field delimiter (default: ,)
• formatValueByType() - Auto-convert numbers, booleans
• supportQuotedField(bool) - Handle quoted fields with embedded delimiters
• indexHeader(num) - Specify header row (default: 0)
• trimHeaderFieldWhiteSpace(bool) - Remove spaces from headers
• ignoreColumnIndexes(indexes) - Exclude specific columns by index from the JSON output
• parseSubArray(delim, sep) - Parse delimited arrays
• mapRows(fn) - Transform, filter, or enrich each row
• getJsonFromStreamAsync(stream) - Process CSV from Readable streams for NodeJS and Browser
• getJsonFromFileStreamingAsync(filePath) - Stream processing for large files for NodeJS and Browser
• getJsonFromFileStreamingAsyncWithCallback(filePath, options = {}) - Parse CSV from a File using streaming with progress callbacks for large files
• utf8Encoding(), latin1Encoding(), etc. - Set file encoding

Examples

fieldDelimiter(char) - Set field delimiter (default: ,)

// Semicolon-delimited
csvToJson.fieldDelimiter(';').getJsonFromCsv('data.csv');

// Tab-delimited
csvToJson.fieldDelimiter('\t').getJsonFromCsv('data.tsv');

// Pipe-delimited
csvToJson.fieldDelimiter('|').getJsonFromCsv('data.psv');

formatValueByType() - Auto-convert numbers, booleans

// Input: name,age,active
//        John,30,true
csvToJson.formatValueByType().getJsonFromCsv('data.csv');
// Output: { name: 'John', age: 30, active: true }

supportQuotedField(bool) - Handle quoted fields with embedded delimiters

// Input: name,description
//        "Smith, John","He said ""Hello"""
csvToJson.supportQuotedField(true).getJsonFromCsv('data.csv');
// Output: { name: 'Smith, John', description: 'He said "Hello"' }

indexHeader(num) - Specify header row (default: 0)

// If headers are in row 2 (3rd line):
csvToJson.indexHeader(2).getJsonFromCsv('data.csv');

trimHeaderFieldWhiteSpace(bool) - Remove spaces from headers

// Input: " First Name ", " Last Name "
csvToJson.trimHeaderFieldWhiteSpace(true).getJsonFromCsv('data.csv');
// Output: { FirstName: 'John', LastName: 'Doe' }

parseSubArray(delim, sep) - Parse delimited arrays

// Input: name,tags
//        John,*javascript,nodejs,typescript*
csvToJson.parseSubArray('*', ',').getJsonFromCsv('data.csv');
// Output: { name: 'John', tags: ['javascript', 'nodejs', 'typescript'] }

ignoreColumnIndexes(indexes) - Exclude specific columns by index

// Input: firstName,lastName,age
//        John,Doe,30
//        Jane,Smith,25
csvToJson.ignoreColumnIndexes([1]).getJsonFromCsv('data.csv');
// Output: [{ firstName: 'John', age: '30' }, { firstName: 'Jane', age: '25' }]

mapRows(fn) - Transform, filter, or enrich each row

// Filter out rows that don't match a condition
const result = csvToJson
  .fieldDelimiter(',')
  .mapRows((row) => {
    // Only keep rows where age >= 30
    if (parseInt(row.age) >= 30) {
      return row;
    }
    return null; // Filters out this row
  })
  .getJsonFromCsv('input.csv');

See mapRows Feature - Usage Guide.

utf8Encoding(), latin1Encoding(), etc. - Set file encoding

// UTF-8 encoding
csvToJson.utf8Encoding().getJsonFromCsv('data.csv');

// Latin-1 encoding
csvToJson.latin1Encoding().getJsonFromCsv('data.csv');

// Custom encoding
csvToJson.customEncoding('ucs2').getJsonFromCsv('data.csv');

getJsonFromStreamAsync(stream) - Process CSV from Readable streams

const fs = require('fs');
const csvToJson = require('convert-csv-to-json');

// Process large files without loading them entirely into memory
async function processLargeCSV() {
  const stream = fs.createReadStream('large-dataset.csv');
  const jsonData = await csvToJson
    .fieldDelimiter(';')
    .supportQuotedField(true)
    .getJsonFromStreamAsync(stream);
    
  console.log(`Processed ${jsonData.length} records efficiently`);
  return jsonData;
}

getJsonFromFileStreamingAsync(filePath) - Stream processing for large files

const csvToJson = require('convert-csv-to-json');

// Most efficient way to process large CSV files
async function processLargeCSV(filePath) {
  const jsonData = await csvToJson
    .fieldDelimiter(',')
    .formatValueByType()
    .getJsonFromFileStreamingAsync(filePath);
    
  console.log(`Streamed and processed ${jsonData.length} records`);
  return jsonData;
}

// Usage - handles files of any size without memory constraints
const data = await processLargeCSV('massive-dataset.csv');

getJsonFromFileStreamingAsyncWithCallback(filePath, options = {}) - Parse CSV from a File object using streaming with progress callbacks for large files

const csvToJson = require('convert-csv-to-json');
const fileInput = document.querySelector('#csvfile').files[0];

 csvToJson.browser.getJsonFromFileStreamingAsyncWithCallback(fileInput, {
   chunkSize: 500,
   onChunk: (rows, processed, total) => {
     console.log(`Processed ${processed}/${total} rows`);
     // Handle chunk of rows here
   },
   onComplete: (allRows) => {
     console.log('Processing complete!');
   },
   onError: (error) => {
     console.error('Error:', error);
   }
 });

See SYNC.md, ASYNC.md or BROWSER.md for complete configuration details.

Example: Complete Workflow

const csvToJson = require('convert-csv-to-json');

async function processCSV() {
  const data = await csvToJson
    .fieldDelimiter(',')
    .formatValueByType()
    .supportQuotedField(true)
    .getJsonFromCsvAsync('data.csv');
  
  console.log(`Parsed ${data.length} records`);
  return data;
}

Migration Guides

• RFC 4180 Breaking Changes - See RFC4180_MIGRATION_GUIDE.md
• Sync to Async Migration - See MIGRATION.md
• Error Handling - See docs/ERROR_HANDLING.md for comprehensive error documentation

Development

Install dependencies:

npm install

Run tests:

npm test

Debug tests:

npm run test-debug

CI/CD GitHub Action

See CI/CD GitHub Action.

Release

When pushing to the master branch:

• Include [MAJOR] in commit message for major release (e.g., v1.0.0 → v2.0.0)
• Include [PATCH] in commit message for patch release (e.g., v1.0.0 → v1.0.1)
• Minor release is applied by default (e.g., v1.0.0 → v1.1.0)

License

CSVtoJSON is licensed under the MIT License.

Support

Found a bug or need a feature? Open an issue on GitHub.

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