Configuration management in Deno - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the configuration file in Deno.

Deno

import config from './config.[1]';

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

Atxt

Bts

Cjs

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Using .json extension without proper import assertion

Using .js extension when the config is in TypeScript

In Deno, configuration files can be TypeScript files. So the correct extension is .ts.

2fill in blank

medium

Complete the code to read environment variables in Deno.

Deno

const port = Deno.env.get('[1]');

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

AENV_PORT

Bport

CSERVER_PORT

DPORT

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase variable names which do not match environment variables

Using custom names not set in environment

Environment variables are case-sensitive and usually uppercase. The common name for the port variable is PORT.

3fill in blank

hard

Fix the error in the code to import a JSON config file with assertion in Deno.

Deno

import config from './config.json' [1];

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

Aassert { type: 'json' }

Bassert { json: true }

Cassert { format: 'json' }

Dassert { type: 'js' }

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect assertion keys or values

Omitting the assertion causing runtime errors

Deno requires an import assertion for JSON files. The correct syntax is assert { type: 'json' }.

4fill in blank

hard

Fill both blanks to create a config object with default values using environment variables.

Deno

const config = {
  port: Number(Deno.env.get('[1]')) || [2],
};

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

APORT

B3000

C8080

DHOST

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for default port

Using wrong environment variable names

The environment variable PORT is read and converted to a number. If not set, it defaults to 3000.

5fill in blank

hard

Fill all three blanks to export a configuration object with environment variables and default values.

Deno

export const config = {
  host: Deno.env.get('[1]') || '[2]',
  port: Number(Deno.env.get('[3]')) || 4000,
};

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

AHOST

Blocalhost

CPORT

D127.0.0.1

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up host and port environment variable names

Using IP address string instead of hostname for default

The host uses environment variable HOST or defaults to localhost. The port uses PORT or defaults to 4000.

Practice

1. What is the main purpose of configuration management in a Deno application?

easy

A. To separate settings like API keys from the main code for flexibility and security

B. To write all code and settings in a single file for simplicity

C. To hardcode secret keys directly in the source code

D. To avoid using environment variables altogether

Solution

1. Step 1: Understand configuration management role

   Configuration management separates settings from code to keep apps flexible and secure.

2. Step 2: Identify correct practice in Deno

   Using environment variables or .env files keeps secrets out of code and allows easy changes.

3. Final Answer:

   To separate settings like API keys from the main code for flexibility and security -> Option A

4. Quick Check:

   Config management = separate settings [OK]

Hint: Remember: keep secrets out of code, use config files [OK]

Common Mistakes:

• Hardcoding secrets in source code
• Mixing code and settings in one file
• Ignoring environment-specific configs

2. Which of the following is the correct way to load environment variables from a .env file in Deno?

easy

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

B. import { config } from "https://deno.land/std/dotenv/mod.ts"; const env = config();

C. import dotenv from "dotenv"; dotenv.load();

D. import { loadEnv } from "deno_env"; loadEnv();

Solution

1. Step 1: Identify Deno's dotenv import syntax

   Deno uses ES module imports from URLs, like importing config from std/dotenv.

2. Step 2: Check correct usage

   Calling config() loads environment variables from .env file correctly in Deno.

3. Final Answer:

   import { config } from "https://deno.land/std/dotenv/mod.ts"; const env = config(); -> Option B

4. Quick Check:

   Deno dotenv import = import { config } from "https://deno.land/std/dotenv/mod.ts"; const env = config(); [OK]

Hint: Use Deno's std/dotenv with ES module import [OK]

Common Mistakes:

• Using Node.js require syntax in Deno
• Using non-existent packages
• Calling wrong functions to load env

3. Given this Deno code snippet:

import { config } from "https://deno.land/std/dotenv/mod.ts";
const env = config();
console.log(env.API_KEY);

If the .env file contains API_KEY=12345, what will be printed?

medium

A. undefined

B. Error: .env file not found

C. API_KEY

D. 12345

Solution

1. Step 1: Understand config() output

   The config() function reads .env and returns an object with keys and values.

2. Step 2: Access API_KEY value

   env.API_KEY accesses the value '12345' from the loaded environment variables.

3. Final Answer:

   12345 -> Option D

4. Quick Check:

   env.API_KEY = '12345' [OK]

Hint: config() returns env vars as object keys [OK]

Common Mistakes:

• Expecting config() to print keys directly
• Forgetting to create .env file
• Assuming env variables are undefined

4. What is wrong with this Deno code snippet for loading environment variables?

import { config } from "https://deno.land/std/dotenv/mod.ts";
const env = config;
console.log(env.API_SECRET);

medium

A. config is not imported correctly

B. API_SECRET is not a valid environment variable name

C. config is assigned without calling it as a function

D. console.log syntax is incorrect

Solution

1. Step 1: Check how config is used

   config is a function and must be called with parentheses to load env variables.

2. Step 2: Identify the error

   Assigning config without () means env is the function itself, not the loaded object.

3. Final Answer:

   config is assigned without calling it as a function -> Option C

4. Quick Check:

   Call config() to load env [OK]

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

Common Mistakes:

• Assigning function reference instead of calling it
• Misspelling config import
• Using wrong variable names

5. You want to manage different configurations for development and production in a Deno app. Which approach is best practice?

hard

A. Use separate .env files like .env.development and .env.production and load the correct one based on an environment variable

B. Hardcode production secrets in the code and use .env only for development

C. Use a single .env file with all keys and comment out unused ones manually

D. Store all secrets in a JSON file checked into version control

Solution

1. Step 1: Understand environment-specific configs

   Different environments need different settings to avoid mistakes and leaks.

2. Step 2: Choose best practice for Deno

   Using separate .env files and loading based on an environment variable keeps configs clean and secure.

3. Final Answer:

   Use separate .env files like .env.development and .env.production and load the correct one based on an environment variable -> Option A

4. Quick Check:

   Separate env files per environment = Use separate .env files like .env.development and .env.production and load the correct one based on an environment variable [OK]

Hint: Use multiple .env files and switch by env variable [OK]

Common Mistakes:

• Hardcoding secrets in code
• Using one .env for all environments
• Checking secrets into version control