TypeScript And let it divide the interface from the code JavaScriptures II Eloy and Sarah 

What even is TypeScript? 

Why did we start using TypeScript? 

Exercises 

Benefits (compared to js) 

● It can make stepping into new repos less daunting Easier to get acclimated to new repos 

● Intellisense in VSCode is slick ● [see example] Tooling 

● When developing in TS (as opposed to normal JS), it’s clear what exactly one expects to happen Keeps code clear 

● It’s nice to be able to easily see the schema of an application as opposed to maintaining it in your head as you go along Speeds up some parts of the dev process 

● When you change something about your schema, you can immediately see where breaking changes exist because the type checker will throw errors Allows you to catch errors sooner 

Drawbacks 

● Currently involves (at least in our case) a complex dance between Babel, Webpack, Node, Jest, and possibly more. However, as we move more projects to Babel 7, we can drastically simplify this by utilising its ability to parse TypeScript code. ● To debug this sort of thing, one has to look at the docs and github issues of several different projects; there is no singular resource for TS tooling (although our Artsy Engineering blog post on the topic comes close) Setting up tooling can be tedious 

● Most JS projects won’t. ● Over 4000 community maintained type declarations at github.com/DefinitelyTyped/DefinitelyTyped. E.g. @types/react on NPM. ● Details on how to write type declarations can be found here: www.typescriptlang.org/docs/handbook/declaration-files/introduction.html Libraries may not come with TS types 

● https://www.typescriptlang.org/docs/handbook/basic-types.html ● https://github.com/basarat/typescript-book ● https://github.com/mike-works/typescript-fundamentals ● https://egghead.io/playlists/typescript-with-react-d922273e Helpful Links