TS变量,枚举,接口

变量

跟JS一样

let a:string = 's'
let b:number = 1
let c:boolean = true
let d:object = {}
let e:null = null
let f:undefined = undefined

//any(任何类型)

let any1:any = 1
let any2:any = 'b'
any1 = {}
any2 = true

枚举

1. 不赋值
   ` bash
   enum Gender {

    Man,
    Woman
   

   }

let gender: Gender = Gender.Woman
console.log(gender) //1
gender = Gender.Man
console.log(gender) //0

2. 赋值

``` bash
enum Gender {
        Man = 'Man',
        Woman = 'Woman'
    }

let gender: Gender = Gender.Woman
console.log(gender) //Woman
gender = Gender.Man
console.log(gender) //Man

void

函数没有返回值

function test():void{
    console.log(1)
}

let a:number = test() //会报错

never

默认情况下null和undefined是所有类型的子类型.例如,null可以赋值给number类型的变量.

type A = string & number
//报错never

接口

描述一个对象必须有什么属性(方法)

    interface Shape {
        head: string,
        body: string
    }

    interface Human {
        name: string
        age: number,
        shape: Shape,
        say(word: string): void
    }

    let tom: Human = {
        name: 'tom',
        age: 28,
        shape: {
            head: '头',
            body: '身体'
        },
        say(word: string) {
            console.log(word)
        }

    }
    tom.say('hello')

1. readonly

只读

interface Human {
    readonly name: string
    age: number

2. 可选属性

interface Human {
    readonly name: string
    age: number,
    like?:Array<string>

3. 假如额外传入参数

  interface Config {
        color?: string,
        width?: number
    }

    function created(config: Config): void {
        console.log(config)
    }

    created({
        age: 'red'
    })

    //会报错

要使用字符串索引签名

interface Config {
        color?: string,
        width?: number,
        [key: string]: any  //添加这一行,意思是key为字符串类型,value为any类型,key
    }

    function created(config: Config): void {
        console.log(config)
    }

    created({
        age: 'red'
    })

4. 使用接口描述一个函数

注意,接口定义参数名只是一个顺序,跟实际函数变量名没有关系

    interface Operation {
        (number1: number, number2: number): number
    }

    let add: Operation = function (n1: number, n2: number): number {
        return n1 + n2
    }
    let result: number = add(1, 2)
    console.log(result)

5. 接口继承

interface Animal {
    move(): void
}

interface Human extends Animal {
    name: string
    age: number
}

let tom: Human = {
    age: 18,
    name: 'tom',
    move() {
        console.log('move')
    }
}

tom.move()

一个接口可以继承多个接口

    interface Animal {
        move(): void
    }

    interface 有机物 {
        c: true
        h: true
        o: true
    }

    interface Human extends Animal, 有机物 {
        name: string
        age: number
    }

    let tom: Human = {
        c: true,
        h: true,
        o: true,
        age: 18,
        name: 'tom',
        move() {
            console.log('move')
        }
    }