Deno vs Node.js comparison

Introduction

Deno and Node.js are tools to run JavaScript outside the browser. Knowing their differences helps you pick the right one for your project.

You want a simple, secure way to run JavaScript on your computer.

You need to use modern JavaScript features without extra setup.

You want built-in tools like a formatter and test runner without installing more packages.

You have an existing Node.js project and wonder if switching to Deno is worth it.

You want to write scripts that run quickly with minimal configuration.

Syntax

Deno

No special syntax here, but both use JavaScript or TypeScript to write code that runs on your computer.

Deno uses ES Modules by default, so you import files with URLs or relative paths.

Node.js traditionally uses CommonJS modules but now supports ES Modules with some setup.

Examples

Deno imports modules directly from URLs without needing a package manager.

Deno

import { serve } from "https://deno.land/std@0.177.0/http/server.ts";

serve(() => new Response("Hello from Deno!"));

Node.js uses require() for modules in CommonJS style by default.

Deno

const http = require('http');

const server = http.createServer((req, res) => {
  res.end('Hello from Node.js!');
});

server.listen(3000);

Node.js can also use ES Modules with import syntax if configured.

Deno

import http from 'node:http';

const server = http.createServer((req, res) => {
  res.end('Hello with ES Modules in Node.js!');
});

server.listen(3000);

Sample Program

This Deno program starts a web server that responds with a greeting. It uses a URL to import the server function.

Deno

// Deno example: simple HTTP server
import { serve } from "https://deno.land/std@0.177.0/http/server.ts";

serve(() => new Response("Hello from Deno!"));

Important Notes

Deno has built-in security. It asks permission before accessing files, network, or environment.

Node.js has a huge ecosystem of packages via npm, which Deno can also use but with extra steps.

Deno supports TypeScript out of the box, so you can run TypeScript files without compiling first.

Summary

Deno is newer, secure by default, and uses modern JavaScript features easily.

Node.js is older, widely used, and has a large package library.

Choose Deno for simplicity and security; choose Node.js for compatibility and ecosystem.

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