Introduction to Deno

Deno.js, created by Ryan Dahl, who also founded Node.js, is a runtime for JavaScript and TypeScript. It's built on the V8 engine and developed in Rust. In this topic, you'll learn about the key features of Deno.js, its differences from Node.js, how to install and set it up, practical usage examples, and how it compares to Node.js.

Key features of Deno

The architecture of Deno offers several impressive features, increasing its attractiveness as a modern runtime for JavaScript and TypeScript. The most important of these is the built-in support for TypeScript, which gives developers a high-quality experience. You can run TypeScript code directly in Deno without needing extra transpilation steps or external packages, making the development process much smoother.

Security is another fundamental aspect of Deno; it's designed to be secure by default. This means scripts can't freely access system files, environment details, or the network. Deno asks for permission explicitly through command-line flags, such as --allow-net for network access, before a script can touch protected system resources.

Another key feature of Deno is its browser compatibility. It aims to match its server-side API with what you would see in a web browser, with full support for the fetch API. This design principle simplifies shifting between front-end and back-end development; it also promotes code consistency in various environments.

Installation and setup

Installing Deno.js is a straightforward process, differing slightly based on the operating system. Here are the general steps for various platforms:

• macOS & Linux: Utilize the CURL command in the terminal:

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

• Windows: Use Powershell for installation:

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

• macOS Alternative: Homebrew can also be used for macOS users:

  brew install deno
  

After installation, verify the installation by running deno --version in the terminal. This command should display the installed version of Deno, ensuring that it's ready for use.

Getting started with Deno

Deno provides an interactive shell known as the Read-Evaluate-Print-Loop (REPL), where you can execute JavaScript and TypeScript expressions on the fly. To access the REPL, simply type deno into your terminal. This mode is excellent for testing small snippets of code or learning Deno's API.

For running scripts, let's say you want to create a "Hello World" script using Deno. You'd write your code in a .ts file like so:

console.log("Hello World!");

Save this as hello_world.ts. To run this script, open the terminal, navigate to the directory where this file is saved, and execute it by typing:

deno run hello_world.ts

Deno will compile the TypeScript and run it, displaying "Hello World!" in the terminal. This demonstrates Deno's capability to execute TypeScript directly, a helpful feature for developers to quickly test and run their code.

Module management and standard library

Deno diverges from traditional JavaScript runtime environments by rejecting the concept of a central package manager. Instead, it leverages the web's architecture, loading modules from any URL. Here's an example of how you would import a module directly in your Deno script:

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

This line fetches the serve function from Deno's standard module library hosted at deno.land. The module is downloaded, cached, and compiled on the first run, and subsequently reused.

The standard library, a collection of modules vetted by the Deno team, encompasses a wide range of functionalities. For instance, if you need to format dates, you could use the datetime module:

import { format } from "https://deno.land/std/datetime/mod.ts";

console.log(format(new Date(), "yyyy-MM-dd"));

This code snippet demonstrates the ease with which developers can utilize Deno's standard library for tasks like date formatting, all without the need for third-party modules. This approach not only reinforces the runtime's commitment to security but also streamlines the development process.

Key features and differences from node.js

In contrasting Deno.js with Node.js, it's essential to understand their distinct features and approaches. While both serve as runtimes for JavaScript, Deno.js was developed to address some of the limitations of Node.js, with particular focus on security, module management, and support for modern web standards. Here's a comparison table highlighting the key differences between Deno.js and Node.js across several important aspects:

This table highlights the significant differences between Deno.js and Node.js, focusing on language support, security, module management, standard library offerings, and API compatibility. These distinctions showcase Deno.js's approach to addressing some of the limitations and complexities associated with Node.js.

Conclusion

Deno provides a safe and up-to-date runtime environment for JavaScript and TypeScript, notable for its inherent TypeScript support and security framework. Its method for managing modules through URLs and a scrutinized standard library illustrates its goal for simplicity and safety. As Deno evolves, it could become an essential tool for developers who seek these characteristics.