أساسيات بيئة تشغيل Deno

Welcome! In this lesson, we'll dive into Deno, a modern, secure runtime for JavaScript and TypeScript.

Created by Ryan Dahl (who also created Node.js), Deno addresses some of the design choices made in Node.js, focusing on security and a great developer experience.

One of Deno's biggest differences is its security model. By default, Deno scripts run in a sandbox, meaning they have no access to:

• The file system
• The network
• Environment variables
• Subprocesses

You must explicitly grant these permissions using command-line flags. This prevents malicious code from doing harm without your knowledge.

Deno comes with a powerful set of built-in tools. Forget installing separate packages for formatting, linting, or testing!

Key tools include:

• deno fmt: Code formatter
• deno lint: Linter for code quality
• deno test: Test runner
• deno doc: Documentation generator
• deno compile: Compiles scripts into self-contained executables

This integrated experience simplifies project setup and maintenance.

Deno supports TypeScript out of the box. This means you can write TypeScript code without needing a separate compilation step or tsconfig.json file.

It also embraces ES Modules, allowing you to import modules directly from URLs, much like how browsers work. No more node_modules folder!

Let's write a simple Deno program. Save this as hello.ts (or .js) and run it with deno run hello.ts.

While both Deno and Node.js are JavaScript runtimes, they have fundamental differences:

• Security: Deno is secure by default (permissions needed), Node.js has full access.
• TypeScript: Deno supports TS natively, Node.js requires transpilation.
• Tooling: Deno has built-in tools (fmt, lint, test), Node.js relies on npm packages.
• Module System: Deno uses URL-based ES Modules, Node.js uses CommonJS (though ES Modules are gaining traction).
• Standard Library: Deno has a robust standard library, Node.js has a smaller core.

Deno exposes a global Deno object that provides access to runtime-specific APIs, like file system operations, network access, and environment variables.

Here's how you can access command-line arguments passed to your script:

To demonstrate Deno's permission model, let's try to read a file. This script will fail without explicit permission.

To run it successfully, you'll need to add the --allow-read flag: deno run --allow-read file_reader.ts

Great job! In this lesson, you've learned about Deno's foundational features:

• Its security-first approach with a granular permission model.
• The convenience of its built-in tooling.
• Native TypeScript and ES Module support.
• The global Deno object for runtime interactions.

These essentials make Deno a powerful and modern runtime for web development, especially at the edge!