基础
大约 1 分钟
数据类型
Number
const n1: number = 20
const n2: number = 1.2
const n3: number = 0xf00d
String
const str: string = "abc"
Boolean
const flag: boolean = true
const err: boolean = false
Null 和 Undefined
const u: undefined = undefined
const n: null = null
Void
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
Array
let list1: number[] = [1, 2, 3]
let list2: Array<number> = [1, 2, 3]
Tuple 元祖
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]
Object
const o1: object = {}
const o2: object = []
let o3: { name: string; age: number } = { name: "rice", age: 18 }
Any
any 表示任何类型都可以
let a: any = 1
a = "abc"
a = false
UnKnown
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
never
类型表示的是那些永不存在的值的类型
Enum 枚举
enum Color {
Blue,
Red,
white,
}
const c: Color = Color.Blue
const cName = Color[1]
console.log(c) //0
console.log(cName) //Red