What are Environment Variables?

• Environment Variables are key-value pairs stored outside the source code.
• Used to store configuration settings like:
  • API keys
  • Database URLs
  • Port numbers
  • Secret tokens
• Keeps sensitive data secure and separate from your application code.

Accessing Environment Variables

• In Node.js, environment variables are accessed using process.env object.

console.log(process.env.PORT); // prints the value of PORT

Setting Environment Variables

Temporarily (per command):

PORT=3000 node app.js

Permanently (using a .env file + dotenv package):

1️⃣ Install dotenv

npm install dotenv

2️⃣ Create a .env file

PORT=3000
DB_URL=mongodb://localhost:27017/mydb
SECRET_KEY=secret#199

3️⃣ Load .env variables in your app

require('dotenv').config();

console.log(process.env.PORT);        // 3000
console.log(process.env.DB_URL);      // mongodb://localhost:27017/mydb

Best Practices

• Never hardcode secrets or environment-specific data in your code.
• Add .env to .gitignore to avoid pushing it to version control.