What is Deno? What are the differences between Deno and Node.js?

Deno is a modern JavaScript and TypeScript runtime environment developed by Ryan Dahl, the creator of Node.js. Deno was designed to address some of Node.js's early design flaws and provide a safer, more streamlined development experience.

Core Features

Deno includes the following core features:

1. Secure by Default: Scripts cannot access the file system, network, or environment variables unless explicitly granted permissions
2. Built-in TypeScript Support: Native TypeScript support without additional transpilation steps
3. Decentralized Module System: Uses URL-based imports, eliminating the need for package.json and node_modules
4. Single Executable: Deno consists of just one executable file with no complex installation process
5. Built-in Toolchain: Includes formatting, testing, linting, bundling, and other development tools
6. Standard Library: Provides audited standard library to ensure code quality

Key Differences from Node.js

Feature	Deno	Node.js
Module System	ES Modules (URL imports)	CommonJS + ES Modules
Package Management	No package.json, direct URL imports	npm + package.json
Security	Secure by default, explicit authorization required	No security restrictions by default
TypeScript	Native support	Requires configuration and transpilation
API Design	Promise-based	Mix of callbacks and Promises
Architecture	Rust + V8	C++ + V8

Permission System

Deno's permission system is central to its security features:

bash
# Grant file system read permission
deno run --allow-read script.ts

# Grant network access permission
deno run --allow-net script.ts

# Grant all permissions (not recommended)
deno run --allow-all script.ts

Module Import Examples

typescript
// Import modules directly from URL
import { serve } from "https://deno.land/std/http/server.ts";

// Import from local files
import { myFunction } from "./utils.ts";

// Use standard library
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

Typical Use Cases

• Web servers and API development
• Command-line tool development
• Automation scripts
• Microservices architecture
• Real-time applications (WebSocket)

Deno is particularly suitable for projects requiring rapid development, security, and a modern development experience.