Getting Started with Deno 2: A Comprehensive Tutorial

Deno 2 is the latest iteration of Deno, a modern JavaScript/TypeScript runtime built on V8. This release introduces significant improvements, including zero-config Node compatibility, a built-in package manager, and enhanced CLI capabilities. This tutorial will guide you through the new features and how to get started with Deno 2.

1. Installation

Before diving into Deno 2, you need to install it. Use the following command to install Deno:

curl -fsSL https://deno.land/install.sh | sh

Once installed, verify the installation by running:

deno --version

This should display Deno 2.x or higher.

2. New Features in Deno 2

Node Compatibility

Deno 2 is now zero-config, Node-compatible and supports package.json, node_modules, and npm workspaces. This allows you to run Node.js packages seamlessly:

{
  "name": "deno2-project",
  "version": "1.0.0",
  "scripts": {
    "start": "deno run mod.ts"
  },
  "dependencies": {
    "@types/node": "^20.11.0",
    "express": "^4.18.2"
  }
}

You can install and run npm packages directly:

npm install
npm start

Package Manager

Deno 2 includes a built-in package manager with commands like deno install/add/remove. These commands respect semver and cache packages globally:

deno install lodash

Backwards Compatibility

Deno 2 is backwards compatible with Deno 1.x, making it safe to adopt incrementally. You can drop existing Deno tools (fmt, lint, test) into Node repositories:

deno fmt --recursive
deno lint --unstable
deno test --file-lock-ignore

JSR Registry

The JSR (JavaScript Registry) is a TypeScript-first ESM registry for cross-runtime libraries. It provides high-quality, TypeScript-compatible packages:

deno install typescript@latest

CLI Boosts

Deno 2 introduces several CLI enhancements:

1. Code signing and compilation:

deno compile main.ts

1. Multi-core serving:

deno serve --unstable

1. Jupyter notebook support:

deno jupyter https://deno.land/x/jupyter@latest

LTS Channel

Deno 2 introduces an LTS (Long-Term Support) channel, providing predictable support windows for production workloads.

3. Getting Started with Deno 2

Step 1: Create a New Project

Create a new directory for your project and navigate into it:

mkdir deno2-project
cd deno2-project

Step 2: Initialize Your Project

Create a simple "Hello, World!" script:

// hello.ts
console.log("Hello, World!");

Run it using Deno:

deno run hello.ts

Step 3: Explore Deno's Capabilities

Installing Modules

Install external modules using the Deno package manager:

deno install https://deno.land/x/[email protected]/mod.ts

Using Modules in Scripts

// script.ts
import _ from 'https://deno.land/x/[email protected]/mod.ts';
console.log(_.chunk(['a', 'b', 'c'], 2)); // Output: ['a', 'c']

Run the script:

deno run script.ts

Running Tasks

You can run Deno tasks using:

deno task build
deno task watch

4. Packaging and Publishing

Step 1: Create a Package

Create a simple package:

// main.ts
export function greet(name: string) {
  return `Hello, ${name}!`;
}

Step 2: Initialize npm Package

Create a package.json file:

{
  "name": "deno-greet",
  "version": "1.0.0",
  "description": "A simple greeting package",
  "main": "main.ts",
  "scripts": {
    "test": "deno test"
  },
  "keywords": [],
  "author": "Your Name",
  "license": "MIT"
}

Step 3: Publish Your Package

Build your package and publish it to npm:

deno build main.ts
npm publish

Step 4: Use Your Package

Install your package in another project:

npm install deno-greet

Step 5: Share Your Package

Share your package with others. They can import it as:

import { greet } from 'deno-greet';

Conclusion

Deno 2 offers a powerful, modern way to build JavaScript and TypeScript applications. With its Node compatibility, built-in package manager, and enhanced CLI capabilities, Deno 2 is the perfect choice for developers looking for a secure and efficient runtime environment. By following this tutorial, you should now have a solid understanding of how to get started with Deno 2 and leverage its features to build robust applications.