【TypeScript】杂货铺（长期更新）

断言用武之地

let someValue: any = 'this is string'
someValue.length // 编译器找不到这个api

// 如何让它找到 使用断言
let strLength: number = (someValue as string).length

ts3.1版本报错问题

// 元祖类型，不能超过越界元素
let arr: [string, number] = ['1', 1]
arr[3] = '1' // error

类的高级使用

class Greeter {
    static standardGreeting = 'Hello , there'
    
    greeting: string
    
    constructor(message?: string) {
        this.greeting = message
    }
    
    greet() {
        if (this.greeting) {
            return 'hello' + this.greeting
        } else {
            return Greeting.standardGreeting
        }
    }
}

let greeter: Greeter
greeter = new Greeter()
console.log(greeter.greet()) // Hello, there

let greeterMaker: typeof Greeter = Greeter
greeterMaker.standardGreeting = 'Hey, there'

let greeter2: Greeter = new Greeter()
console.log(greeter.greet()) // Hey, there