TypeScript：如何从函数类型中获取许多参数

Question

有什么好方法可以从函数类型中获取许多参数？

例如，我有两个回调函数作为函数类型和一个setter函数。 我想从函数类型中获取一些参数，并用它替换幻数（2，3）。

type Callback1 = (a: number, b: string) => void;
type Callback2 = (a: number, b: string, b: boolean) => void;

setCallback(callback: Callback1 | Callback2): void {
    if (callback.length == 2) {
        this.callback = callback as Callback1;
    } else if (callback.length == 3) {
        this.callback = callback as Callback2;
    }
}

Answer 1

使用length属性。

let x = function (a,b){}
function bar (a,b){}
console.log(x.length, bar.length); // 2,2 

更多

https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Function/length

Answer 2

这对我有用。 如果函数类型的定义发生更改，则伪函数定义的编译将失败。 这比上面的魔术数字安全得多。

type Callback1 = (a: number, b: string) => void;
type Callback2 = (a: number, b: string, b: boolean) => void;

private readonly dummyCallback1: Callback1 = (a: number, b: string) => {};
private readonly dummyCallback2: Callback2 = (a: number, b: string, b: boolean) => {};

setCallback(callback: Callback1 | Callback2): void {
    if (callback.length == this.dummyCallback1.length) {
        this.callback = callback as Callback1;
    } else if (callback.length == this.dummyCallback2.length) {
        this.callback = callback as Callback2;
    }
}

Answer 3

这要简单得多。 谢谢@torazaburo

type Callback = (a: number, b: string, c?: boolean) => void;

setCallback(callback: Callback): void {
    this.callback = callback as Callback1;
}


setCallback(0, "a");
setCallback(0, "a", true);