TOML vs JSON: Complete Comparison and Node.js Usage Guide

Configuration files are essential in modern development. Two popular formats, TOML and JSON, serve different purposes and have distinct advantages. This guide will help you understand when to use each format and how to work with them in Node.js.

What is TOML?

TOML (Tom's Obvious, Minimal Language) is a configuration file format designed to be easy to read and write. It was created by Tom Preston-Werner, co-founder of GitHub.

TOML Example

toml(30 lines, showing 15)

1# config.toml
2title = "My Application"
3version = "1.0.0"
4 
5[database]
6host = "localhost"
7port = 5432
8username = "admin"
9password = "secret123"
10ssl = true
11 
12[server]
13host = "0.0.0.0"
14port = 3000
15timeout = 30

What is JSON?

JSON (JavaScript Object Notation) is a lightweight data-interchange format that's widely used for APIs, configuration files, and data storage.

JSON Example

json(33 lines, showing 15)

1{
2  "title": "My Application",
3  "version": "1.0.0",
4  "database": {
5    "host": "localhost",
6    "port": 5432,
7    "username": "admin",
8    "password": "secret123",
9    "ssl": true
10  },
11  "server": {
12    "host": "0.0.0.0",
13    "port": 3000,
14    "timeout": 30
15  },

Key Differences

1. Readability

TOML:

More human-readable

Supports comments

Better for configuration files

Easier to edit manually

JSON:

Less readable for complex nested structures

No comments (though some parsers support them)

More verbose

Better for programmatic generation

2. Data Types

TOML Supports:

Strings, integers, floats, booleans

Dates and times

Arrays and tables

Inline tables

Array of tables

JSON Supports:

Strings, numbers, booleans

Arrays

Objects

null

3. Comments

TOML:

toml

1# This is a comment
2name = "value"  # Inline comment

JSON:

json

1{
2  // Comments are not officially supported
3  "name": "value"
4}

4. Use Cases

TOML is better for:

Configuration files (Cargo.toml, pyproject.toml, package.json alternatives)

Human-edited settings

Documentation in code

CI/CD configuration

JSON is better for:

API responses

Data exchange between services

Programmatically generated files

Web applications

NoSQL databases

Working with TOML in Node.js

Installation

bash

1npm install @iarna/toml
2# or
3npm install toml

Using @iarna/toml (Recommended)

javascript(27 lines, showing 15)

1const fs = require('fs');
2const TOML = require('@iarna/toml');
3 
4// Reading TOML file
5try {
6  const tomlContent = fs.readFileSync('config.toml', 'utf-8');
7  const config = TOML.parse(tomlContent);
8  
9  console.log(config.title);
10  console.log(config.database.host);
11  console.log(config.users);
12} catch (error) {
13  console.error('Error parsing TOML:', error);
14}
15

Complete TOML Example

javascript(55 lines, showing 15)

1// config-loader.js
2const fs = require('fs');
3const path = require('path');
4const TOML = require('@iarna/toml');
5 
6class ConfigLoader {
7  constructor(configPath) {
8    this.configPath = configPath;
9    this.config = null;
10  }
11 
12  load() {
13    try {
14      const content = fs.readFileSync(this.configPath, 'utf-8');
15      this.config = TOML.parse(content);

Working with JSON in Node.js

Native JSON Support

javascript(25 lines, showing 15)

1const fs = require('fs');
2 
3// Reading JSON file
4try {
5  const jsonContent = fs.readFileSync('config.json', 'utf-8');
6  const config = JSON.parse(jsonContent);
7  
8  console.log(config.title);
9  console.log(config.database.host);
10} catch (error) {
11  console.error('Error parsing JSON:', error);
12}
13 
14// Writing JSON file
15const config = {

Advanced JSON Handling

javascript(96 lines, showing 15)

1// json-utils.js
2const fs = require('fs').promises;
3const path = require('path');
4 
5class JSONConfigManager {
6  constructor(configPath) {
7    this.configPath = configPath;
8    this.config = null;
9  }
10 
11  async load() {
12    try {
13      const content = await fs.readFile(this.configPath, 'utf-8');
14      this.config = JSON.parse(content);
15      return this.config;

Converting Between TOML and JSON

TOML to JSON

javascript(16 lines, showing 15)

1const fs = require('fs');
2const TOML = require('@iarna/toml');
3 
4function tomlToJson(tomlPath, jsonPath) {
5  try {
6    const tomlContent = fs.readFileSync(tomlPath, 'utf-8');
7    const parsed = TOML.parse(tomlContent);
8    const jsonString = JSON.stringify(parsed, null, 2);
9    fs.writeFileSync(jsonPath, jsonString);
10    console.log('Converted TOML to JSON successfully');
11  } catch (error) {
12    console.error('Conversion error:', error);
13  }
14}
15

JSON to TOML

javascript(16 lines, showing 15)

1const fs = require('fs');
2const TOML = require('@iarna/toml');
3 
4function jsonToToml(jsonPath, tomlPath) {
5  try {
6    const jsonContent = fs.readFileSync(jsonPath, 'utf-8');
7    const parsed = JSON.parse(jsonContent);
8    const tomlString = TOML.stringify(parsed);
9    fs.writeFileSync(tomlPath, tomlString);
10    console.log('Converted JSON to TOML successfully');
11  } catch (error) {
12    console.error('Conversion error:', error);
13  }
14}
15

Real-World Examples

Example 1: Express.js Configuration

Using TOML (config.toml):

toml(21 lines, showing 15)

1[app]
2name = "My Express App"
3env = "production"
4port = 3000
5 
6[database]
7type = "postgresql"
8host = "localhost"
9port = 5432
10name = "mydb"
11user = "admin"
12password = "secret"
13 
14[redis]
15host = "localhost"

Using JSON (config.json):

json(24 lines, showing 15)

1{
2  "app": {
3    "name": "My Express App",
4    "env": "production",
5    "port": 3000
6  },
7  "database": {
8    "type": "postgresql",
9    "host": "localhost",
10    "port": 5432,
11    "name": "mydb",
12    "user": "admin",
13    "password": "secret"
14  },
15  "redis": {

Loading in Express.js:

javascript

1// Using TOML
2const TOML = require('@iarna/toml');
3const fs = require('fs');
4const config = TOML.parse(fs.readFileSync('config.toml', 'utf-8'));
5 
6// Using JSON
7const config = require('./config.json');
8 
9// Express app setup
10const express = require('express');
11const app = express();
12 
13app.listen(config.app.port, () => {
14  console.log(`${config.app.name} running on port ${config.app.port}`);
15});

Example 2: Environment-Specific Configuration

javascript(30 lines, showing 15)

1// config-loader.js
2const fs = require('fs');
3const TOML = require('@iarna/toml');
4 
5function loadConfig(env = 'development') {
6  const configPath = `config.${env}.toml`;
7  
8  if (!fs.existsSync(configPath)) {
9    throw new Error(`Config file ${configPath} not found`);
10  }
11  
12  const content = fs.readFileSync(configPath, 'utf-8');
13  const config = TOML.parse(content);
14  
15  // Override with environment variables

Example 3: Package Configuration

package.toml (alternative to package.json):

toml(18 lines, showing 15)

1[package]
2name = "my-project"
3version = "1.0.0"
4description = "My awesome project"
5main = "index.js"
6 
7[scripts]
8start = "node index.js"
9test = "jest"
10build = "webpack"
11 
12[dependencies]
13express = "^4.18.0"
14lodash = "^4.17.21"
15

Performance Comparison

Parsing Speed

javascript(27 lines, showing 15)

1const fs = require('fs');
2const TOML = require('@iarna/toml');
3 
4// Benchmark function
5function benchmark(name, fn, iterations = 1000) {
6  const start = process.hrtime.bigint();
7  for (let i = 0; i < iterations; i++) {
8    fn();
9  }
10  const end = process.hrtime.bigint();
11  const duration = Number(end - start) / 1000000; // Convert to milliseconds
12  console.log(`${name}: ${duration.toFixed(2)}ms (${(duration / iterations).toFixed(4)}ms per operation)`);
13}
14 
15// Test files

Results:

JSON parsing is typically faster (native support)

TOML parsing is slightly slower but still very fast

For most applications, the difference is negligible

When to Use Each Format

Use TOML When:

✅ Configuration files that humans need to edit

✅ Documentation needs to be embedded

✅ Comments are important

✅ Working with Rust, Python, or other TOML-native ecosystems

✅ CI/CD configuration files

✅ Project metadata (like Cargo.toml)

Use JSON When:

✅ API responses and requests

✅ Data exchange between services

✅ Programmatically generated files

✅ Web applications (browser-native support)

✅ NoSQL databases

✅ When comments aren't needed

✅ When maximum compatibility is required

Best Practices

TOML Best Practices

toml(19 lines, showing 15)

1# Use comments to document configuration
2# Database connection settings
3[database]
4# PostgreSQL connection string
5host = "localhost"
6port = 5432
7 
8# Use tables for logical grouping
9[server.production]
10port = 8080
11 
12[server.development]
13port = 3000
14 
15# Use arrays for multiple values

JSON Best Practices

json

1{
2  "version": "1.0.0",
3  "config": {
4    "database": {
5      "host": "localhost",
6      "port": 5432
7    }
8  },
9  "features": {
10    "enabled": [
11      "auth",
12      "logging"
13    ],
14    "disabled": [
15      "debug"
16    ]
17  }
18}

Migration Guide

Migrating from JSON to TOML

javascript

1// migrate-to-toml.js
2const fs = require('fs');
3const TOML = require('@iarna/toml');
4 
5function migrateJsonToToml(jsonPath, tomlPath) {
6  const jsonContent = fs.readFileSync(jsonPath, 'utf-8');
7  const jsonData = JSON.parse(jsonContent);
8  const tomlContent = TOML.stringify(jsonData);
9  fs.writeFileSync(tomlPath, tomlContent);
10  console.log(`Migrated ${jsonPath} to ${tomlPath}`);
11}
12 
13migrateJsonToToml('package.json', 'package.toml');

Migrating from TOML to JSON

javascript

1// migrate-to-json.js
2const fs = require('fs');
3const TOML = require('@iarna/toml');
4 
5function migrateTomlToJson(tomlPath, jsonPath) {
6  const tomlContent = fs.readFileSync(tomlPath, 'utf-8');
7  const tomlData = TOML.parse(tomlContent);
8  const jsonContent = JSON.stringify(tomlData, null, 2);
9  fs.writeFileSync(jsonPath, jsonContent);
10  console.log(`Migrated ${tomlPath} to ${jsonPath}`);
11}
12 
13migrateTomlToJson('config.toml', 'config.json');

Conclusion

Both TOML and JSON have their place in modern development:

TOML excels at human-readable configuration files with comments and better readability

JSON is the standard for APIs, data exchange, and web applications

Key Takeaways:

Use TOML for configuration files that need comments and human editing

Use JSON for APIs, data exchange, and when you need native browser support

Both formats work well in Node.js with appropriate libraries

Performance differences are minimal for most use cases

Choose based on your specific needs and team preferences

For Node.js applications, you can use both formats effectively. TOML is great for application configuration, while JSON remains the standard for APIs and data exchange.

Additional Resources

[TOML Specification](https://toml.io/)

[@iarna/toml npm package](https://www.npmjs.com/package/@iarna/toml)

[JSON Specification](https://www.json.org/)

[Node.js fs module](https://nodejs.org/api/fs.html)

Happy coding!

TOML vs JSON: Complete Comparison and Node.js Usage Guide

What is TOML?

TOML Example

What is JSON?

JSON Example

Key Differences

1. Readability

2. Data Types

3. Comments

4. Use Cases

Working with TOML in Node.js

Installation

Using @iarna/toml (Recommended)

Complete TOML Example

Working with JSON in Node.js

Native JSON Support

Advanced JSON Handling

Converting Between TOML and JSON

TOML to JSON

JSON to TOML

Real-World Examples

Example 1: Express.js Configuration

Example 2: Environment-Specific Configuration

Example 3: Package Configuration

Performance Comparison

Parsing Speed

When to Use Each Format

Use TOML When:

Use JSON When:

Best Practices

TOML Best Practices

JSON Best Practices

Migration Guide

Migrating from JSON to TOML

Migrating from TOML to JSON

Conclusion

Additional Resources

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