如何列出给定对象的所有 get 属性？

Question

Give the class:

export class Foo
{
    #x: number;
    #y : number;

    constructor()
    {
        this.#x = 20;
        this.#y = 10;
    }

    public get a(): string { return "baa"; }
    public get n(): number { return 20; }
}

How can I get the getters properties ie, ["a", "n"] ? I have no code to show yet, I've looked reflect and reflect-metadata and I couldn't find anything to list those. I'm using typescript but javascript solutions are welcome too.

Answer 1

You can iterate over the property descriptors of the prototype (or of the object and every one of its prototypes) and see if the descriptor has a get function.

 const logGetters = obj => { if (!obj) return; for (const [key, desc] of Object.entries(Object.getOwnPropertyDescriptors(obj))) { if (desc.get && key !== '__proto__') console.log(key); // exclude Object.prototype getter } logGetters(Object.getPrototypeOf(obj)); }; class Foo { #x; #y; constructor() { this.#x = 20; this.#y = 10; } get a() { return "baa"; } get n() { return 20; } } const f = new Foo(); logGetters(f);

For Typescript, just annotate with const logGetters = (obj: object) => { .

Answer 2

You can filter over Object.getOwnPropertyDescriptors .

 class Foo { #x; #y; constructor() { this.#x = 20; this.#y = 10; } get a() { return "baa"; } get n() { return 20; } } const res = Object.entries(Object.getOwnPropertyDescriptors(Foo.prototype)) .filter(([k, d])=>typeof d.get === 'function').map(([k])=>k); console.log(res);