Using Environment Variables in Node.js

What You’ll Learn 📚

• What environment variables are and why they’re important
• How to set up and use environment variables in Node.js
• Common pitfalls and how to avoid them
• Practical examples and exercises to solidify your understanding

Introduction to Environment Variables

Environment variables are like little secret notes that your application can read to understand its environment. They help your app adapt to different settings without changing the code. Imagine them as instructions you give to your app about how it should behave in different scenarios.

Key Terminology

• Environment Variable: A key-value pair used to configure the environment in which an application runs.
• Process.env: An object in Node.js that stores all environment variables.

Getting Started with a Simple Example 🌱

// Step 1: Create a file named '.env' in your project root with the following content:
// PORT=3000

// Step 2: Create a file named 'index.js' with the following content:
require('dotenv').config(); // Load environment variables from .env file

console.log('Your app is running on port:', process.env.PORT);

Progressively Complex Examples

Example 1: Using Environment Variables for Configuration

// .env
// DB_HOST=localhost
// DB_USER=root
// DB_PASS=s1mpl3

// index.js
require('dotenv').config();

const dbConfig = {
  host: process.env.DB_HOST,
  user: process.env.DB_USER,
  password: process.env.DB_PASS
};

console.log('Database Configuration:', dbConfig);

Example 2: Environment Variables for Different Environments

// .env.development
// API_URL=https://dev.api.example.com

// .env.production
// API_URL=https://api.example.com

// index.js
require('dotenv').config({ path: `.env.${process.env.NODE_ENV}` });

console.log('API URL:', process.env.API_URL);

Example 3: Handling Missing Environment Variables

require('dotenv').config();

if (!process.env.API_KEY) {
  throw new Error('Missing API_KEY environment variable');
}

console.log('API Key:', process.env.API_KEY);

Common Questions and Answers

1. What are environment variables used for?

   They are used to configure application settings without hardcoding them into your codebase.

2. How do I set environment variables?

   You can set them in a .env file or directly in your system’s environment settings.

3. Why use the dotenv package?

   It simplifies loading environment variables from a .env file into process.env.

4. What if an environment variable is missing?

   Your application might fail or behave unexpectedly. It’s good practice to handle such cases gracefully.

5. Can I use environment variables in production?

   Yes, they are commonly used in production to manage configuration settings.

Troubleshooting Common Issues

Ensure your .env file is not committed to version control as it may contain sensitive information.

If your environment variables are not loading, check if the dotenv package is installed and properly configured.

Remember to restart your Node.js application after changing environment variables to ensure changes take effect.

Practice Exercises 🏋️‍♂️

• Create a new Node.js project and set up environment variables for a mock API configuration.
• Experiment with different .env files for different environments and switch between them using NODE_ENV.
• Try handling missing environment variables by providing default values or throwing errors.

Great job making it through this tutorial! 🎉 Keep practicing, and soon, using environment variables will feel like second nature. Happy coding! 💻