TypeScript

                                let a: number = 4
let b: string = 'hello'
let b2: 'hello' = 'hello'
let c: boolean = true
let d: string[] = ['one', 'two']
let e: any = 3
let f: undefined = undefined
let g: null = null

function j(a: string): string | number {
    return ''
}

const h = (a: number): number => {
    return 1
}

d = d.map((x: string) => x.toLowerCase())

function k(c: {a: number | string, b?: number}): void {}

type action = 'up' | 'down' // enum

type Point = {
    x: number,
    y: number,
}
type D3Point = Point & {
    z: number,
}
interface IPoint {
    x: number,
    y: number,
}
interface IPoint {
    a: string,
}
interface iD3Point extends IPoint {
    z: number,
}
function print(p: Point) {}

const l = (point: IPoint) => {
    const m: iD3Point = point as iD3Point
}
Список