学习 Typescript（一）

let isDone: boolean = false
let age: number = 10
let firstName: string = 'viking'let message: string = `Hello, ${firstName}`
let u: undefined = undefinedlet n:null = null
let num: number = undefined

let notSure: any = 4notSure = 'maybe a string'notSure = true
notSure.myNamenotSure.getName()

let arr: number[] = [1,2,3]arr.push(3)
// arguments类数组 IArguments类型，不是Arrayfunction test(){    console.log(arguments);    arguments.length    arguments[0]}

let user: [string, number] = ['abc', 20]user.push('1212')	只能push已有类型

interface IPerson{    readonly id: number;    // 只读属性    name: string    age: number    address?: string    // 可选属性}
let lihua: IPerson = {    id: 1,    name: 'lihua',    age: 20}

function add(x: number, y: number, z?: number): number {    if (typeof z === 'number') {        return x + y + z    } else {        return x + y    }}add(1, 2)add(1, 2, 3)

const add =  (x: number, y: number, z?: number): number => {    if (typeof z === 'number') {        return x + y + z    } else {        return x + y    }}
interface ISum{    (x: number, y: number, z?: number):number}let add2: ISum = add