Typescript Cheat Sheet

interface Building { room: { door: string, walls: string[], }; } type Walls = Building['room']['walls']; // string[] 

export interface User { ... } 

class Greeter<T> { greeting: T constructor(message: T) { this.greeting = message } } let greeter = new Greeter<string>('Hello, world') 

class Point { x: number y: number static instances = 0 constructor(x: number, y: number) { this.x = x this.y = y } } 

class Point {...} class Point3D extends Point {...} interface Colored {...} class Pixel extends Point implements Colored {...} 

class Point { static instances = 0; constructor( public x: number, public y: number, ){} } 

class Point { public someUselessValue!: number; ... } 

interface User { ... } function getUser(callback: (user: User) => any) { callback({...}) } getUser(function (user: User) { ... }) 

type Name = string | string[] 

{ [key: string]: Object[] } 

interface User { readonly name: string } 

interface User { name: string, age?: number } 

interface LabelOptions { label: string } function printLabel(options: LabelOptions) { ... }