Configuration management in Deno

Introduction

Configuration management helps your program know important settings like database info or API keys without changing the code. It keeps your app flexible and safe.

When you want to keep secret keys safe and not write them directly in your code.

When your app needs different settings for development and production.

When you want to change settings without changing the program code.

When you want to share the same code but use different configurations on different computers.

Syntax

Deno

import { config } from "https://deno.land/std@0.203.0/dotenv/mod.ts";

const env = await config();

console.log(env.MY_SETTING);

Use the config() function to load environment variables from a .env file.

The await keyword is needed because config() returns a promise.

Examples

This loads environment variables and prints the value of PORT from your .env file.

Deno

import { config } from "https://deno.land/std@0.203.0/dotenv/mod.ts";

const env = await config();
console.log(env.PORT);

This loads variables and also sets them in Deno's environment so you can use Deno.env.get().

Deno

import { config } from "https://deno.land/std@0.203.0/dotenv/mod.ts";

const env = await config({ export: true });
console.log(Deno.env.get("API_KEY"));

This loads variables from a specific file named .env.production.

Deno

import { config } from "https://deno.land/std@0.203.0/dotenv/mod.ts";

const env = await config({ path: ".env.production" });
console.log(env.DATABASE_URL);

Sample Program

This program loads configuration from a .env file and prints which port the server will use. If PORT is not set, it uses 3000 by default.

Deno

import { config } from "https://deno.land/std@0.203.0/dotenv/mod.ts";

// Load environment variables from .env file
const env = await config();

// Use a setting from the config
const port = env.PORT || "3000";

console.log(`Server will run on port: ${port}`);

Important Notes

Always keep your .env file out of public code repositories to protect secrets.

You can use different .env files for different environments like development and production.

Use await because loading config is asynchronous in Deno.

Summary

Configuration management keeps your app flexible and secure by separating settings from code.

Use Deno's dotenv module to load settings from .env files easily.

Always protect your secret keys and use different configs for different environments.

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