To use environment variables in a Node.js application, install dotenv, create a .env file to store your variables, and access them in your code.

Using environment variables in a Node.js application is essential for managing configurations, especially sensitive information like API keys, database connections, and other settings that should not be hard-coded. This guide will help you set up and use environment variables effectively in your application:

1. Prerequisites: Ensure you have Node.js and npm installed. Familiarity with Node.js basics and configuration management concepts will be beneficial.

2. Initialize Your Project: Create a new directory for your project and navigate to it in your terminal. Run npm init -y to generate a package.json file.

3. Install dotenv: To manage environment variables, install the dotenv package by running:

   npm install dotenv
   

   This package allows you to load environment variables from a .env file into your Node.js application.

4. Create a .env File: In the root directory of your project, create a new file named .env. This file will hold your environment variables in the format KEY=VALUE. For example:

   PORT=3000
   DB_URL=mongodb://localhost:27017/mydatabase
   API_KEY=your_api_key_here
   

   Make sure to never commit this file to your version control system, especially if it contains sensitive information.

5. Load Environment Variables in Your Code: In your main JavaScript file (e.g., server.js), require and configure dotenv at the very top:

   require('dotenv').config();
   

   This loads the environment variables from your .env file into process.env, which is a global object available throughout your Node.js application.

6. Accessing Environment Variables: You can now access your environment variables anywhere in your code using process.env.VARIABLE_NAME. For example:

   const PORT = process.env.PORT || 3000;
   const DB_URL = process.env.DB_URL;
   console.log(`Server running on port: ${PORT}`);
   

   This code sets the server port from the environment variable or defaults to 3000 if not set.

7. Best Practices:

   • Never hard-code sensitive information: Always use environment variables to store sensitive data.
   • Use a .env.example file: Create a .env.example file that contains the keys without actual values. This file can serve as documentation for other developers on what environment variables are needed.
   • Add .env to .gitignore: Make sure to add your .env file to .gitignore to prevent it from being tracked by Git.

8. Conclusion: By following these steps, you can effectively manage configuration settings and sensitive information in your Node.js applications using environment variables. This approach promotes security and flexibility in your application development.