Deno

JaxNode July 2020

Deno pronounced

Dee-No

What is Deno

  • A runtime for TypeScript and JavaScript
  • Built with Rust, v8, Tokio, TypeScript and JS
  • CLI tools
  • Webservers
  • Micro-services
  • Back-end server tools

History

  • Ryan Dahl introduced Node.js 2009
  • He left the project 2012
  • Node became extremely popular
  • Dahl introduced Deno two years ago

Is Deno a replacement

for Node?

  • No

Node shortcomings

  • Everything is asynchronous
  • Forces developers to program using callbacks
  • Dahl liked Go's approach to synchronous with channels
  • Modules not always compatible with browsers
  • No 'window' object
  • No built in fetch

Deno features

  • Write in either TypeScript or JavaScript
  • Not tied to NPM
  • Standard Core library
  • Full support for 'import' and 'export'
  • Deno.land site hosts some modules
  • Enhanced security through flags

Deno shortcomings

  • 1.0, now 1.2
  • Not full support for 3rd party services
  • Not backwards compatible with NPM
  • Requires flags for some features to work
  • Is it safe to use in Prod?

Deno

  • Chocolatey (Windows)
  • Homebrew (macOS)
  • Cargo
  • Shell
  • PowerShell

Install

  • choco install deno
  • brew install deno
  • cargo install deno 
  • curl -fsSL https://deno.land/x/install/install.sh | sh

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

Sample

// hello.ts
const message: string = 'Hello JaxNode!';
console.log(message);

// run the following command > deno run hello.ts
// httpserve.ts
import { serve } from "https://deno.land/std@0.59.0/http/server.ts";
const s = serve({ port: 8000 });
console.log("http://localhost:8000/");
for await (const req of s) {
  req.respond({ body: "Hello World\n" });
}

Security flags

  • deno run --allow-net
  • --allow-net=api.google.com
  • deno run --allow-write
  • deno run --allow-read
  • --allow-read=/tmp
  • deno run --allow-all
  • deno run --allow-env

Existing frameworks

  • Oak for webservices
  • opine (Express clone)
  • lodash
  • moment
  • redis

Package managers

  • deno.land
  • pika.dev
  • jspm.io

Modules

  • No 'node_modules' folder
  • modules are downloaded and cached in the $HOME/Library/Cache/deno
  • Can also store in your src

Deno Tooling

  • Use Cargo to create specific Deno builds
  • Deno bundle
  • Deno Test
  • Deno Linter
  • Deno Install
  • Deno info
  • Deno fmt

Deno Test

  • asserts.ts module had a bug in 1.12
  • Looks for files that 'test' in the filename
  • Create tests with Deno.test(name, fn())

Deno Install

  • > deno install
  • deno install --allow-net --allow-read -n serve https://deno.land/std/http/file_server.ts -p 8080
  • > cd ~/ && serve

WebAssembly

  • Deno supports WASM through V8 
  • Deno is compiled with Rust
  • Many Deno modules have coded in Rust, and converted into WebAssembly
  • SQLite Deno module is C compiled into Wasm with emscripten

Deploying Deno

  • Host as a Server app
  • Deploy using Docker
  • Heroku has a buildpack for Deno, will require Procfile
  • Vercel (formally Zeit) lets you deploy deno as micro-services

Demo Deno

Questions?

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