ts怎么推断泛型实例对象的属性?

Question

如图- 我要怎么样才能推断出userName和password这两个属性呢

Answer 1

class C {
    userName: string
}

function f<
    T extends new (...args: any[]) => any,
    K extends keyof InstanceType<T>
>(cls: T, data: K) {

}

f(C, 'userName')

Answer 2

const fun = <T extends new (...args: any[]) => any, K = keyof InstanceType<T>>(cls: T, data: K) => {

}

Answer 3

你传入的不是实例对象，而是构造函数本身。

const user = new User()

fun(user, 'userName')