When building modern applications, especially in multi-environment setups like development, QA, and production, managing environment-specific configurations efficiently is crucial. Manually switching environment settings can be error-prone and time-consuming. This guide demonstrates how to automate the process using Node.js and a simple script.

Problem Statement

In a project with multiple environments, we often have separate configuration files for each environment. Instead of manually renaming or replacing these files when switching environments, we can automate this process with a script.

For example, if we have three environments: dev, qa, and prod, we can use a script to dynamically copy the corresponding configuration file to a unified env.json file.

Prerequisites

• Node.js installed on your system.
• Basic knowledge of Node.js file system (fs) and path modules.

Folder Structure

Ensure your environment configuration files are organized as follows:

project-root/
│
├── src/
│   ├── config/
│       └── scripts/
│           └── set-environment.js
│   └── envs/
│       ├── dev.json
│       ├── qa.json
│       ├── prod.json
│       └── env.json

• dev.json, qa.json, prod.json: Contain environment-specific configurations.
• env.json: The active environment configuration file (automatically generated).
• set-environment.js: The script to automate the environment setup.

Environment Configuration Files

env.json

This file will be dynamically generated by the script. Here's the format:

{
  "API_URL": "",
  "ENVIRONMENT": ""
}

prod.json

For production:

{
  "API_URL": "https://prod.example.com",
  "ENVIRONMENT": "production"
}

dev.json

For production:

{
  "API_URL": "https://dev.example.com",
  "ENVIRONMENT": "development"
}

qa.json

For QA:

{
  "API_URL": "https://qa.example.com",
  "ENVIRONMENT": "qa"
}

The Automation Script

Below is the set-environment.js script:

const fs = require('fs');
const path = require('path');

// Map environment names to JSON files
const envMapping = {
    dev: 'dev.json',
    qa: 'qa.json',
    prod: 'prod.json',
};

// Get the environment argument
const environment = process.argv[2];
console.log("🚀 ~ environment:", environment);

if (!environment || !envMapping[environment]) {
  console.error(`Invalid or missing environment argument. Use one of: ${Object.keys(envMapping).join(', ')}`);
  process.exit(1);
}

// Resolve paths for source and destination files
const sourceFile = path.resolve(__dirname, `../envs/${envMapping[environment]}`);
const destinationFile = path.resolve(__dirname, '../envs/env.json');

// Check if the source file exists
if (!fs.existsSync(sourceFile)) {
  console.error(`Environment file not found: ${sourceFile}`);
  process.exit(1);
}

// Copy the selected file to `env.json`
fs.copyFileSync(sourceFile, destinationFile);
console.log("🚀 ~ Environment set to:", environment);

Adding NPM Scripts

To simplify the usage of the script, add the following commands to the scripts section of your package.json:

"scripts": {
    "env:dev": "node ./src/config/scripts/set-environment.js dev",
    "env:qa": "node ./src/config/scripts/set-environment.js qa",
    "env:prod": "node ./src/config/scripts/set-environment.js prod"
}

How It Works

1. Environment Mapping: The script uses an envMapping object to map environment names (dev, qa, prod) to their corresponding JSON files (dev.json, qa.json, prod.json).

2. Command-Line Argument: The desired environment (e.g., dev) is passed as a command-line argument.

3. File Path Resolution: Using the path module, the script dynamically identifies the source file (dev.json) and the destination file (env.json).

4. File Existence Check: Before copying, the script ensures that the source file exists, avoiding runtime errors.

5. File Copy Operation: The fs.copyFileSync method copies the selected configuration file to env.json.

Using the Script

Run the following commands to set the environment:

• For Development:

npm run env:dev

• For QA:

npm run env:qa

• For Production:

npm run env:prod

Benefits

• Automation: Eliminates manual file management.
• Error Prevention: Reduces the risk of incorrect configurations.
• Flexibility: Easily extendable for additional environments.

Conclusion

Automating environment configuration is a simple yet powerful way to improve workflow efficiency in your project. With this setup, you can seamlessly switch between environments with just a single command.

Happy coding! 🚀