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Is there a way to read environment variables in Node.js code?

Yes! In Node.js, you can access environment variables through the built-in process.env object. These variables are typically set outside of your Node.js code—often in your operating system’s environment, in a Docker container, or from a CI/CD pipeline. Below are the most common ways to read environment variables:

1. Using process.env Directly

// server.js
const port = process.env.PORT || 3000;
console.log('Server will run on port:', port);
  • Here, process.env.PORT will pull the value of the PORT environment variable.
  • If it’s undefined, we use a default fallback: 3000.

Setting Environment Variables

  • macOS/Linux: 
    PORT=5000 node server.js
  • Windows (cmd.exe): 
    set PORT=5000 && node server.js
  • PowerShell: 
    $env:PORT=5000; node server.js

2. Using a .env File with dotenv

A popular approach for local development is to create a .env file that stores your environment variables. Then use the dotenv library to load them into process.env:

  1. Install dotenv:

    npm install dotenv

  2. Create a .env file in your project root:

    PORT=3000
DB_HOST=localhost
DB_USER=myuser
DB_PASS=mypassword

  3. Load variables in code:

    // server.js
require('dotenv').config(); // load .env into process.env

const port = process.env.PORT || 3000;
console.log('Server will run on port:', port);

console.log('DB Host:', process.env.DB_HOST);
console.log('DB User:', process.env.DB_USER);
console.log('DB Password:', process.env.DB_PASS);

Important Notes

  • Do not commit your .env file to public repositories if it contains sensitive data (like passwords or API keys).
  • You can list .env in your .gitignore to ensure it stays out of version control.

3. Best Practices for Managing Environment Variables

  1. Avoid Committing Secrets

    • Use local .env files or environment configuration on your hosting platform, but don’t store sensitive data in code repositories.

  2. Use a Library

    • dotenv is widely adopted for local dev. In production (e.g., Docker, Kubernetes, or cloud hosting), environment variables are often set at the infrastructure level.

  3. Validate Variables

    • For critical environment variables, consider using a validation library or custom checks to ensure they are defined before your app proceeds.

  4. Keep Production Config Out of Dev

    • Maintain separate .env files or environment management for each stage (development, staging, production) to avoid mixing credentials or configurations.

Recommended Resource

Summary

  • Native Approach: Use process.env.VARIABLE_NAME directly in your code.
  • Local Development: Rely on dotenv and a .env file to easily manage environment variables.
  • Production: Typically set variables via the hosting environment or deployment scripts.

This approach ensures your application logic stays flexible and secure, separating environment-specific details (like ports, database credentials, or API keys) from your codebase.

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