基础

llz大约 1 分钟

数据类型

const n1: number = 20
const n2: number = 1.2
const n3: number = 0xf00d

const str: string = "abc"

const flag: boolean = true
const err: boolean = false

Null 和 Undefined

const u: undefined = undefined
const n: null = null

void 类型表示没有任何类型。void 类型只能赋值为 undefined，当一个函数没有返回值时，其返回值类型是 void

function withoutRes(): void {
  console.log("No return of any")
}

//void类型只能赋值为undefined
const a: void = undefined

基本数据类型还是 symbol、bigint

let list1: number[] = [1, 2, 3]
let list2: Array<number> = [1, 2, 3]

元组类型表示一个已知元素数量和类型的数组，各元素的类型不必相同

const list: [string, number] = ["a", 1]

const o1: object = {}
const o2: object = []

let o3: { name: string; age: number } = { name: "rice", age: 18 }

any 表示任何类型都可以

let a: any = 1
a = "abc"
a = false

let notSure: unknown = 4;
notSure = "aa";
notSure = false;

unkonwn类型的值不能赋值给any和unknown之外的类型变量，any则可以,如下：

let un:unknown=2

//ok
un='111'

//ok
let b:any=un

//Error: Type  unknown  is not assignable to type  string
let a:string=un

never 类型表示的是那些永不存在的值的类型

enum Color {
  Blue,
  Red,
  white,
}

const c: Color = Color.Blue
const cName = Color[1]

console.log(c) //0
console.log(cName) //Red