dotenv for environment configuration in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to load environment variables from a .env file.

Node.js

require('[1]').config();
console.log(process.env.MY_VAR);

Drag options to blanks, or click blank then click option'

Adotenv

Bexpress

Chttp

Dfs

Attempts:

3 left

💡 Hint

Common Mistakes

Using other packages like express or fs instead of dotenv.

The dotenv package loads environment variables from a .env file into process.env.

2fill in blank

medium

Complete the code to access the environment variable named PORT.

Node.js

const port = process.env.[1] || 3000;
console.log(`Server runs on port ${port}`);

Drag options to blanks, or click blank then click option'

APORT

Bport

CPath

DHOST

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'port' instead of uppercase 'PORT'.

Environment variables are case-sensitive. The variable is named PORT in uppercase.

3fill in blank

hard

Fix the error in the code to correctly load environment variables.

Node.js

import dotenv from '[1]';
dotenv.[2]();
console.log(process.env.SECRET_KEY);

Drag options to blanks, or click blank then click option'

Aconfig

Bdotenv

Cexpress

Dload

Attempts:

3 left

💡 Hint

Common Mistakes

Importing from wrong package names like 'express' or 'load'.

The package name to import is dotenv. The method to load variables is config().

4fill in blank

hard

Fill both blanks to create a .env file and load a variable named API_KEY.

Node.js

API_KEY=[1]

require('dotenv').[2]();
console.log(process.env.API_KEY);

Drag options to blanks, or click blank then click option'

A"12345abcde"

Bconfig

Cload

D"apikey"

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the value or using wrong method name to load variables.

The .env file stores variables as key=value pairs. The value should be quoted if it contains letters and numbers. The method to load is config().

5fill in blank

hard

Fill all three blanks to create a Node.js script that loads dotenv, reads PORT, and starts a server.

Node.js

import dotenv from '[1]';
dotenv.[2]();
const port = process.env.[3] || 8080;

Drag options to blanks, or click blank then click option'

Adotenv

Bconfig

CPORT

Dexpress

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong package names or method names, or wrong variable case.

Import dotenv, call config() to load variables, then read PORT from process.env.

Practice

1. What is the main purpose of using dotenv in a Node.js project?

easy

A. To manage database connections automatically

B. To compile JavaScript code faster

C. To load environment variables from a file into process.env

D. To create HTTP servers easily

Solution

1. Step 1: Understand what dotenv does

   dotenv reads a file (usually .env) and loads variables into process.env.

2. Step 2: Identify the main purpose

   This allows your app to access secret or environment-specific settings safely without hardcoding them.

3. Final Answer:

   To load environment variables from a file into process.env -> Option C

4. Quick Check:

   dotenv loads env vars = C [OK]

Hint: dotenv loads .env variables into process.env [OK]

Common Mistakes:

• Thinking dotenv compiles or runs code
• Confusing dotenv with database or server tools
• Expecting dotenv to manage app logic

2. Which of the following is the correct way to load environment variables using dotenv in a Node.js file?

easy

A. require('dotenv').config()

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

C. dotenv.setup()

D. require('dotenv').loadEnv()

Solution

1. Step 1: Recall the dotenv usage syntax

   The official and common way to load variables is calling require('dotenv').config() at the start of your app.

2. Step 2: Check other options for correctness

   The other options use incorrect method names or syntax not supported by dotenv.

3. Final Answer:

   require('dotenv').config() -> Option A

4. Quick Check:

   Use config() method to load dotenv [OK]

Hint: Use require('dotenv').config() to load env vars [OK]

Common Mistakes:

• Using wrong method names like load or setup
• Forgetting to call config() function
• Trying to import dotenv without config call

3. Given the following code and .env file, what will be the output?

// .env file content
API_KEY=12345
PORT=8080

require('dotenv').config();
console.log(process.env.API_KEY);
console.log(process.env.PORT);

medium

A. undefined\nundefined

B. null\nnull

C. API_KEY\nPORT

D. 12345\n8080

Solution

1. Step 1: dotenv loads variables from .env into process.env

   After calling require('dotenv').config(), process.env.API_KEY is set to "12345" and process.env.PORT is set to "8080" as strings.

2. Step 2: console.log prints the values

   The console will output the values exactly as strings, separated by new lines.

3. Final Answer:

   12345 8080 -> Option D

4. Quick Check:

   dotenv loads vars as strings = 12345\n8080 [OK]

Hint: dotenv sets process.env vars as strings from .env [OK]

Common Mistakes:

• Expecting numbers instead of strings
• Not calling config() before accessing vars
• Assuming variables are undefined without loading dotenv

4. What is the error in the following code snippet that prevents environment variables from loading correctly?

const dotenv = require('dotenv');
dotenv.config;
console.log(process.env.SECRET_KEY);

medium

A. Missing parentheses after config function call

B. dotenv package not installed

C. SECRET_KEY not defined in .env file

D. Using require instead of import

Solution

1. Step 1: Check how dotenv.config is called

   The code uses dotenv.config; without parentheses, so the function is not executed.

2. Step 2: Understand the effect of missing parentheses

   Without calling config(), environment variables are not loaded into process.env, so SECRET_KEY remains undefined.

3. Final Answer:

   Missing parentheses after config function call -> Option A

4. Quick Check:

   Call config() with () to load env vars [OK]

Hint: Always call config() with parentheses to load env [OK]

Common Mistakes:

• Forgetting parentheses on config function
• Assuming require auto-executes config
• Ignoring missing .env file or variable

5. You want to use dotenv to load different environment variables for development and production. Your .env file has NODE_ENV=development and API_URL=http://localhost:3000. You also have a .env.production file with NODE_ENV=production and API_URL=https://api.example.com. How can you load the correct file based on the environment?

hard

A. Use dotenv.loadEnv(process.env.NODE_ENV) to auto-load

B. Call require('dotenv').config({ path: `.env.${process.env.NODE_ENV}` }) after setting NODE_ENV

C. Rename .env.production to .env manually before running

D. Call require('dotenv').config() only once without options

Solution

1. Step 1: Understand dotenv supports custom paths

   dotenv's config function accepts a path option to specify which file to load.

2. Step 2: Use NODE_ENV to select the file dynamically

   By calling require('dotenv').config({ path: `.env.${process.env.NODE_ENV}` }), you load .env.development or .env.production based on the environment.

3. Final Answer:

   Call require('dotenv').config({ path: `.env.${process.env.NODE_ENV}` }) after setting NODE_ENV -> Option B

4. Quick Check:

   Use config({ path }) to load env files by environment [OK]

Hint: Use config({ path: `.env.${NODE_ENV}` }) to load env files [OK]

Common Mistakes:

• Not specifying path option for different env files
• Manually renaming files instead of dynamic loading
• Using nonexistent dotenv.loadEnv method