Deno vs Node.js comparison - Hands-On Comparison

Deno vs Node.js Comparison Project

📖 Scenario: You are building a simple Deno script to compare basic features of Deno and Node.js. This will help you understand how Deno handles modules, permissions, and runtime differences compared to Node.js.

🎯 Goal: Create a Deno script that sets up a basic data structure comparing Deno and Node.js features, configures a permission setting, processes the data with a loop, and finally exports the comparison results.

📋 What You'll Learn

Create a dictionary called features with exact keys and values comparing Deno and Node.js

Add a boolean variable called allowNetwork set to true

Use a for loop with variables feature and description to iterate over features.entries()

Export the final features dictionary using export keyword

💡 Why This Matters

🌍 Real World

Understanding the differences between Deno and Node.js helps developers choose the right runtime for their projects and write compatible code.

💼 Career

Many modern backend and full-stack developer roles require knowledge of JavaScript runtimes like Node.js and Deno, including module systems and security models.

1

DATA SETUP: Create the features dictionary

Create a dictionary called features with these exact entries: 'Module System': 'Deno uses ES Modules by default', 'Permissions': 'Deno requires explicit permission flags', 'Package Manager': 'Deno does not use npm', 'Runtime': 'Deno is built on V8 and Rust'

Deno

# Your code here

Hint

Use new Map() with an array of key-value pairs for the features.

2

CONFIGURATION: Add a permission flag variable

Add a boolean variable called allowNetwork and set it to true to represent network permission in Deno

Deno

const features = new Map([
  ['Module System', 'Deno uses ES Modules by default'],
  ['Permissions', 'Deno requires explicit permission flags'],
  ['Package Manager', 'Deno does not use npm'],
  ['Runtime', 'Deno is built on V8 and Rust']
]);

// Your code here

Hint

Declare allowNetwork as a constant boolean set to true.

3

CORE LOGIC: Loop through features and log descriptions

Use a for loop with variables feature and description to iterate over features.entries() and add a comment inside the loop describing the feature

Deno

const features = new Map([
  ['Module System', 'Deno uses ES Modules by default'],
  ['Permissions', 'Deno requires explicit permission flags'],
  ['Package Manager', 'Deno does not use npm'],
  ['Runtime', 'Deno is built on V8 and Rust']
]);

const allowNetwork = true;

// Your code here

Hint

Use for (const [feature, description] of features.entries()) to loop through the Map.

4

COMPLETION: Export the features Map

Export the features Map using the export keyword at the end of the file

Deno

const features = new Map([
  ['Module System', 'Deno uses ES Modules by default'],
  ['Permissions', 'Deno requires explicit permission flags'],
  ['Package Manager', 'Deno does not use npm'],
  ['Runtime', 'Deno is built on V8 and Rust']
]);

const allowNetwork = true;

for (const [feature, description] of features.entries()) {
  // Feature: feature, Description: description
}

// Your code here

Hint

Use export { features }; to make the features Map available outside this module.

Practice

1. Which of the following is a key security feature of Deno compared to Node.js?

easy

A. Node.js has built-in sandboxing for all scripts.

B. Deno allows all file and network access without restrictions.

C. Deno runs code with restricted permissions by default.

D. Node.js requires explicit permission flags for network access.

Solution

1. Step 1: Understand Deno's default security model

   Deno runs scripts with no file, network, or environment access unless explicitly allowed.

2. Step 2: Compare with Node.js default behavior

   Node.js allows full access by default without permission restrictions.

3. Final Answer:

   Deno runs code with restricted permissions by default. -> Option C

4. Quick Check:

   Deno security = restricted by default [OK]

Hint: Remember: Deno locks down access unless you say otherwise [OK]

Common Mistakes:

• Thinking Node.js restricts permissions by default
• Assuming Deno allows all access without flags
• Confusing Node.js and Deno security models

2. Which syntax correctly runs a Deno script with network access permission?

easy

A. deno run --allow-net script.ts

B. node run --allow-net script.ts

C. deno run script.ts --allow-net

D. node run script.ts --allow-net

Solution

1. Step 1: Recall Deno command structure

   Deno uses deno run followed by permission flags before the script name.

2. Step 2: Identify correct flag placement

   The flag --allow-net must come before the script file name.

3. Final Answer:

   deno run --allow-net script.ts -> Option A

4. Quick Check:

   Deno run + flags before script [OK]

Hint: Flags come before script name in Deno commands [OK]

Common Mistakes:

• Placing flags after the script name
• Using Node.js commands for Deno
• Mixing up 'node' and 'deno' commands

3. What will the following Deno code output if run without any permission flags?

console.log("Reading file...");
const data = await Deno.readTextFile("example.txt");
console.log(data);

medium

A. PermissionDenied: read access to 'example.txt' is not allowed

B. Contents of example.txt printed

C. SyntaxError due to await outside async function

D. FileNotFoundError if example.txt does not exist

Solution

1. Step 1: Check permission requirements for file reading

   Deno requires explicit --allow-read permission to read files.

2. Step 2: Analyze code run without permissions

   Running without --allow-read causes a PermissionDenied error when reading a file.

3. Final Answer:

   PermissionDenied: read access to 'example.txt' is not allowed -> Option A

4. Quick Check:

   Deno file read needs permission [OK]

Hint: Deno blocks file reads without --allow-read flag [OK]

Common Mistakes:

• Assuming file reads work without permission
• Confusing syntax errors with permission errors
• Ignoring Deno's security model

4. Identify the error in this Node.js code snippet compared to Deno's approach:

import { serve } from "https://deno.land/std/http/server.ts";
serve(() => new Response("Hello"));

medium

A. Node.js needs the 'serve' function to be called with 'new'.

B. Node.js cannot import modules directly from URLs like Deno.

C. Node.js does not support async functions.

D. Node.js requires 'require' instead of 'import'.

Solution

1. Step 1: Understand module import differences

   Deno supports direct URL imports; Node.js does not support this natively.

2. Step 2: Identify Node.js module system

   Node.js uses local files or npm packages, not direct URL imports.

3. Final Answer:

   Node.js cannot import modules directly from URLs like Deno. -> Option B

4. Quick Check:

   Node.js import URL support = no [OK]

Hint: Node.js needs local or npm modules, not URL imports [OK]

Common Mistakes:

• Thinking Node.js supports URL imports
• Confusing import syntax with async support
• Assuming 'new' is needed for serve function

5. You want to build a secure web server that only allows network access and no file system access. Which setup best fits this requirement using Deno and Node.js?

hard

A. Use Node.js with node --allow-net server.js to restrict file access.

B. Use Node.js with node server.js and rely on default security.

C. Use Deno with deno run server.ts without flags to allow all access.

D. Use Deno with deno run --allow-net server.ts to restrict file access.

Solution

1. Step 1: Identify security needs

   The server should allow only network access, no file system access.

2. Step 2: Compare Deno and Node.js permission models

   Deno allows fine-grained permission control via flags; Node.js does not restrict by default.

3. Step 3: Choose correct command

   deno run --allow-net server.ts grants network access only, blocking file system access.

4. Final Answer:

   Use Deno with deno run --allow-net server.ts to restrict file access. -> Option D

5. Quick Check:

   Deno permission flags enable precise access control [OK]

Hint: Deno flags control access; Node.js lacks default restrictions [OK]

Common Mistakes:

• Assuming Node.js restricts access by default
• Using Deno without flags allows no permissions
• Thinking Node.js supports --allow-net flag