Mug in Clermont | LavaJUG | Clermont'ech, March 2019

Premier Field Engineer @spontoreau In ❤️ with Co-organizer

@ParisTypeScript

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https://github.com/Microsoft/TypeScript

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transpile ts js $ tsc config

Editors tsserver server.ts Language Service service.ts TS standalone compiler tsc.ts Core TypeScript Compiler core.ts, emitter.ts, checker.ts, parser.ts, …

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{ "name": "angular-with-dts", "version": "1.0.0", "dependencies": { "angular": "1.5.8" }, "devDependencies": { "@types/angular":"1.5.20" } } $ npm install --save-dev @types/angular package.json:

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let str: string; let array: number[] = [1, 2, 3]; function fn(param: boolean): void { // Do something }

interface Rocket { boosters: number; launch: () => void; } class Soyuz implements Rocket { boosters : number; constructor() { this.boosters = 4; } launch(): void { … }; } let soyuzT15: Rocket = new Soyuz(); let soyuzMS3: Soyuz = new Soyuz(); Class or Interface… How to choose?

any

class Rocket { name: string; boosters: number; } class Cat { name: string; } function playWithKitten(kitten: Cat) { // Do something } const rocket: Rocket = { name: "Soyuz", boosters: 4 }; const cat: Cat = { name: "Grumpy" }; playWithKitten(cat); playWithKitten(rocket); // ☺

• TypeScript is JavaScript. • Interface is only a TypeScript compiler concept (type checking). • Sometime you have to deal with the any type (Example: third part). • The Duck example: const duck = { fly: () => console.log("I can fly!"), swim: () => console.log("I can swin!"), feather: true }; const penguin = { swim: () => console.log("I can swin!"), feather: true }; const isDuck = (obj: any) => (obj.hasOwnProperty("feather") && obj.fly && obj.swim); if(isDuck(duck)) { (duck).fly(); } if(!isDuck(penguin)) { console.log("Penguin can't fly...") }

interface Rocket { boosters: number; launch?: () => void; } Read-only: interface Rocket { readonly boosters: number; launch?: () => void; } interface Launch { () => void; } Function: Cannot be implemented by a class !

abstract class Rocket { boosters: string; abstract launch(): void; } class Soyuz extends Rocket { } class Soyuz extends Rocket { launch(): void { throw new Error("Not implemented."); } }

abstract class Rocket { readonly boosters: number; constructor(boosters: number) { this.boosters = boosters; } abstract launch() : void; } class RocketFactory { ctor: new (boosters: number) => T; constructor(ctor: new (boosters: number) => T) { this.ctor = ctor; } create(boosters: number): T { return new this.ctor(boosters); } }

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Types === static constraints • Type categories: • primitive • object • union • intersection • Special type: • any • null • undefined • void • Type alias type Bool = boolean;

The light version ☺ undefined null void number primitive string boolean any object array class interface function

Discriminated Union Intersection Union Type Guards Mapped Conditional Infer Immutability

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