dotenv for environment configuration in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this dotenv usage code?

Consider this Node.js code using dotenv to load environment variables. What will be logged to the console?

Node.js

import dotenv from 'dotenv';
dotenv.config();
console.log(process.env.APP_NAME);

A The value of APP_NAME from the .env file

B undefined

C Throws ReferenceError because dotenv is not imported correctly

D Throws SyntaxError due to missing dotenv config call

💡 Hint

Remember dotenv loads variables from .env into process.env when config() is called.

dotenv.config() reads the .env file and sets process.env variables. So console.log prints the APP_NAME value if defined.

❓ component_behavior

intermediate

How does dotenv behave when .env file is missing?

If you run a Node.js app with dotenv but the .env file is missing, what happens?

A dotenv.config() returns an error and stops the app

B dotenv.config() throws a runtime exception

C dotenv.config() returns an object with an error property but app continues

D dotenv.config() silently creates a new empty .env file

💡 Hint

Check dotenv.config() return value when .env is missing.

dotenv.config() returns an object with an error property if .env is missing, but does not throw or stop the app.

📝 Syntax

advanced

Which option correctly loads dotenv in ES module syntax?

You want to use dotenv in a Node.js ES module. Which code snippet correctly loads and configures dotenv?

A const dotenv = require('dotenv'); dotenv.config();

B import dotenv from 'dotenv'; dotenv.config();

C import { config } from 'dotenv'; config();

D import * as dotenv from 'dotenv'; dotenv.load();

💡 Hint

Remember ES modules use import syntax and dotenv.config() is the correct method.

Options B and C both use ES module import syntax and call config(), which is correct for ES modules.

🔧 Debug

advanced

Why does process.env.VAR remain undefined after dotenv.config()?

Given this code: import dotenv from 'dotenv'; console.log(process.env.MY_VAR); dotenv.config(); console.log(process.env.MY_VAR); MY_VAR is defined in .env. Why is the first console.log undefined?

A dotenv.config() must be called before accessing process.env variables

B MY_VAR is misspelled in .env file

C Node.js caches process.env before dotenv runs

D dotenv.config() does not load variables automatically

💡 Hint

Think about when dotenv loads variables relative to when you read them.

dotenv.config() loads variables into process.env. Accessing process.env before config() runs shows undefined.

🧠 Conceptual

expert

What is the best practice for managing multiple environment files with dotenv?

You have different environment files like .env.development and .env.production. How should you load the correct one using dotenv?

A dotenv automatically detects and loads .env.production if NODE_ENV=production

B Manually specify path in dotenv.config({ path: '.env.production' }) based on NODE_ENV

C Rename the desired file to .env before running the app

D Use multiple dotenv.config() calls for each file

💡 Hint

dotenv.config() accepts a path option to specify which file to load.

dotenv does not auto-detect environment files. You must specify the path manually based on environment.