@deepu105 #devoxxUkraine By Deepu K Sasidharan, XebiaLabs November 2, 2019 Building Native TypeScript applications using Deno 

@deepu105 #devoxxUkraine About Me Deepu K Sasidharan OSS aficionado Co-lead Senior developer Robotics & Astronomy enthusiast https://www.packtpub.com/application-development/full-stack-development-jhipster 

@deepu105 #devoxxUkraine About XebiaLabs 

@deepu105 #devoxxUkraine What about you? How many of you are JavaScript developers? How many are web developers? Who likes TypeScript more than JavaScript? Any NodeJS application developers? 

@deepu105 #devoxxUkraine What about you? Have you heard of Deno? 

@deepu105 #devoxxUkraine What is Deno? A modern JavaScript/TypeScript runtime & scripting environment Created by Ryan Dahl(Creator of NodeJS) in 2018 Built with V8, Rust and Tokio Secure by default Built in tooling Execute remote scripts Lightweight multi-platform executable(~10MB) Many inspirations from Go and Rust https://deno.land/ 

Does not use NPM No more node_modules hell! 

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@deepu105 #devoxxUkraine 

@deepu105 #devoxxUkraine What is TypeScript A strict syntactical superset of JavaScript - upto ES2019(ES10) JavaScript that scales Optional static typing support Transpiles to JavaScript Maintained by Microsoft with major collaboration from Google Great editor and IDE support 

@deepu105 #devoxxUkraine Why 

@deepu105 #devoxxUkraine Why TypeScript Type safety and Type inference Great IDE support Easier refactoring Better linting and error identification Features from the Future Additional language features Much better code style 

I hate transpiling my code, but if have to do so I’ll do it with TypeScript 

Getting started! 

@deepu105 #devoxxUkraine Install Deno brew install deno or cargo install deno_cli or curl -fsSL https://deno.land/x/install/install.sh | sh Or using PowerShell iwr https://deno.land/x/install/install.ps1 -useb | iex 

Main features 

@deepu105 #devoxxUkraine Execute remote scripts deno https://deno.land/std/examples/welcome.ts 

@deepu105 #devoxxUkraine Secure by default Scripts can't access files, the environment, subprocesses or the network unless specifically allowed by the script during execution or with flags --allow-all --allow-env --allow-write --allow-net --allow-run ● Granular permissions ● Permissions can be revoked ● Permissions whitelist support 

@deepu105 #devoxxUkraine Secure by default 

@deepu105 #devoxxUkraine Standard modules ● colors - ANSI colors on console ● datetime - Datetime parse utilities ● encoding - Read CSV & TOML ● flags - CLI argument parser ● fs - Filesystem API ● http - HTTP server framework ● log - Logging framework ● media_types - Resolve media types ● prettier - Prettier formatting API ● strings - String utils ● testing - Testing utils ● uuid - UUID support ● ws - Websocket client/server 

@deepu105 #devoxxUkraine Supports only ES Modules ● require() is not supported, so no confusion with import syntax ● No "magical" module resolution ● Third party modules are imported by URL(Local and remote) ● Remote code is fetched only once and catched globally for later use ● Remote code is considered immutable and never updated unless --reload flag is used ● Dynamic imports ● Supports import maps ● Third party modules in https://deno.land/x/ ● NPM modules can be used if required as simple local file URL or from https://jspm.io/ or https://www.pika.dev/ 

@deepu105 #devoxxUkraine Supports only ES Modules 

@deepu105 #devoxxUkraine Built in tooling ● dependency inspector (deno info) ● Bundler (deno bundle) ● Installer (deno install) ● Test runner (deno test) ● Type info (deno types) ● code formatter, uses prettier (deno fmt) ● linter [planned] (deno lint) ● Debugger [planned] (--debug) 

@deepu105 #devoxxUkraine Browser compatibility ● Deno programs which are written completely in JavaScript and do not use the global Deno ● Deno programs in Typescript bundled into JavaScript and do not use the global Deno 

@deepu105 #devoxxUkraine Async actions return promise ● No call back hell ● Consistent API across the standard modules ● Works great with async/await 

@deepu105 #devoxxUkraine Top level await ● Simplifies code ● Makes code more readable ● Works great with Deno async API 

@deepu105 #devoxxUkraine Web assembly support https://wasdk.github.io/WasmFiddle/?pkku4 

@deepu105 #devoxxUkraine Subprocess using web workers ● Async API ● Uses web workers ● One V8 instance per worker 

@deepu105 #devoxxUkraine Options 

Why is Deno better than NodeJS 

@deepu105 #devoxxUkraine Advantages ● Easy to install - Single lightweight binary ● Secure by default, Fine grained privileges ● Simpler module resolution ● Decentralized and globally cached third party modules ● No dependency on package managers or package registries(No NPM, No Yarn, No node_modules) ● Native TypeScript support ● Follows web standards and modern language features ● Remote script runner ● Built in tooling 

Why does it matter 

@deepu105 #devoxxUkraine Why does it matter ● Dynamic languages are still important ○ Data science ○ Scripting ○ Tooling ○ CLI ● NodeJS ecosystem has become too heavy and bloated ● Many Python/NodeJS use cases can be replaced with TypeScript using Deno ○ TypeScript provides better developer experience ○ Consistent and documentable API ○ Easier to build and distribute ○ Does not download the internet all the time ○ More secure 

@deepu105 #devoxxUkraine Challenges ● Fragmentation ○ Not compatible with most of the NPM modules ○ Lib authors would have to publish a Deno compatible build(Not difficult but en extra step) ● Migrating existing NodeJS apps will not be easy due to incompatible API ● Bundles are not optimized so might need tooling or improvements there ● Stability as Deno is quite new (NodeJS is battle tested) ● Not production ready 

@deepu105 #devoxxUkraine A Deno proxy application in action $ deno install my-proxy deno_app.ts --allow-net $ my-proxy https://google.com 

Still in active development 

1.0 planned for end of year https://github.com/denoland/deno/issues/2473 

10 Things I Regret About Node.js - Ryan Dahl - https://www.youtube.com/watch?v=M3BM9TB-8yA Deno, a new way to JavaScript - Ryan Dahl - https://www.youtube.com/watch?v=z6JRlx5NC9E Website - https://deno.land/ 

https://jhipster.tech @java_hipster Full Stack Development with JHipster ● Amazon: https://goo.gl/k1NBAv ● Packt: https://goo.gl/XvQLeN 

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