Deno Cheatsheet

Deno is a runtime for JavaScript and TypeScript that is built on the V8 JavaScript engine. It is designed to be secure, simple, and reliable. Here's a cheat sheet to help you get started with Deno:

Installation

Using Shell (Linux/macOS):

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

Using PowerShell (Windows):

iwr https://deno.land/x/install/install.ps1 -useb | iex

Using Chocolatey (Windows):

choco install deno

Basic Commands

• deno run : Run a TypeScript or JavaScript file.
• deno eval "console.log('Hello, Deno!')": Execute JavaScript/TypeScript code directly.
• deno info : Display information about the TypeScript/JavaScript file.
• deno repl: Start an interactive REPL (Read-Eval-Print Loop).

Permissions

Deno has a permission-based model for accessing resources. When you run a script, it may need certain permissions to perform actions like accessing the file system or network. Use the --allow-* flags to grant permissions.

• --allow-read: Read access to files and directories.
• --allow-write: Write access to files and directories.
• --allow-net: Network access.
• --allow-env: Access to environment variables.
• --allow-run: Execute other programs.

Example:

deno run --allow-read myscript.ts

Package Management

Deno uses ES modules for importing dependencies. You can import modules directly from URLs or use a package manager like deno.land/x.

• Import from URL: import { something } from 'https://deno.land/x/something/mod.ts';

Dependency Locking

• Generate a lock.json file: deno cache --lock=lock.json --lock-write deps.ts
• Use the lock.json file to ensure reproducible builds: deno cache --lock=lock.json

Third-Party Tools

Deno has several third-party tools and libraries available:

• Oak: A middleware framework for building web applications. GitHub: https://github.com/oakserver/oak
• DenoDB: A simple and efficient database toolkit for Deno. GitHub: https://github.com/eveningkid/denodb
• Deno Postgres: A PostgreSQL database driver for Deno. GitHub: https://github.com/buildondata/deno-postgres
• oakCors: Middleware for enabling CORS in Oak. GitHub:https://github.com/oakserver/oak/blob/main/middleware/cors.ts

TypeScript Support

Deno has excellent TypeScript support by default. You can use TypeScript features like type checking and interfaces seamlessly.

Deno CLI Flags

• --allow-all: Grants all permissions (use with caution).
• --unstable: Enables unstable APIs.

Upgrade Deno

To upgrade Deno to the latest version, you can use the following command:

deno upgrade

This cheat sheet covers the basics of Deno. For more in-depth information and documentation, please visit the official Deno website: https://deno.land/