process.env for environment variables in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is process.env in Node.js?

process.env is an object in Node.js that holds environment variables as key-value pairs. It allows your app to access system or user-defined settings.

beginner

How do you access an environment variable named PORT in Node.js?

<p>You access it using <code>process.env.PORT</code>. For example, <code>const port = process.env.PORT;</code></p>

beginner

Why should sensitive data like API keys be stored in environment variables instead of code?

Storing sensitive data in environment variables keeps secrets out of your codebase. This helps protect them from being exposed if the code is shared or published.

beginner

What happens if you try to access an environment variable that is not set?

If the variable is not set, process.env.VARIABLE_NAME returns undefined. You can provide a default value to avoid errors.

intermediate

How can you set environment variables for a Node.js app when running it locally?

You can set them inline before the command, like PORT=3000 node app.js on Unix systems, or use a .env file with packages like dotenv.

What type of value does process.env store for each environment variable?

A Strings

B Numbers

C Booleans

D Objects

All environment variable values in process.env are strings.

How do you safely provide a default port if process.env.PORT is undefined?

A const port = process.env.PORT ? null : 3000;

B const port = 3000 || process.env.PORT;

C const port = process.env.PORT && 3000;

D const port = process.env.PORT || 3000;

Using || returns the first truthy value, so if process.env.PORT is undefined, it uses 3000.

Which package helps load environment variables from a .env file in Node.js?

A express

B dotenv

C nodemon

D cors

dotenv loads variables from a .env file into process.env.

Why is it a bad idea to hardcode API keys directly in your Node.js code?

A It makes the code run slower

B It causes syntax errors

C It exposes secrets if code is shared

D It prevents the app from starting

Hardcoding secrets risks exposing them publicly if the code is shared or pushed to repositories.

What will console.log(process.env.MY_VAR) output if MY_VAR is not set?

A undefined

B null

C empty string

D 0

Accessing an unset environment variable returns undefined.

Explain how to use process.env to manage configuration in a Node.js app.

Think about how environment variables help keep your app flexible and secure.

Describe how to set environment variables locally and how to load them automatically in Node.js.

Consider both manual and automated ways to provide environment variables.