JavaScript - 实例的复制方法

Question

我想要复制类实例的所有属性/方法的可能性:

class A {
    get prop1() { return 1; }
    get prop2() { return 2; }

    doStuff() {
        return this.prop1 + this.prop2;
    }
}

class B extends A {
   get prop1() { return 5; }
}

class AWrapper {
    constructor(a) {
        // [1] Copy all methods/propertys of a
        this.doStuff = () => a.doStuff() + 42;
    }
}

const a = new A();
const b = new B();
const wA = new AWrapper(a);
const wB = new AWrapper(b);
console.log(a.prop1(), wA.prop1(), wB.prop1()); // 1, 1, 5
console.log(a.doStuff(), wA.doStuff()); // 3, 45

我可以手动复制每个方法/属性，但是[1] 是否有一个简单的命令，使得wA 具有与a 相同的签名?

Answer 1

通常，Proxy是使用 mixin 或装饰器时的首选工具:

class A {
    get prop1() {
        return 1;
    }

    get prop2() {
        return 2;
    }

    doStuff() {
        return this.prop1 + this.prop2;
    }
}


class B extends A {
    get prop1() {
        return 5;
    }
}


function decorate(target) {
    let mixin = {
        doStuff() {
            return target.doStuff() + 42;
        }
    }

    return new Proxy(target, {
        get(_, prop) {
            return (prop in mixin) ? mixin[prop] : target[prop];
        }
    });
}


const a = new A();
const b = new B();

const wA = decorate(a)
const wB = decorate(b)

console.log(a.prop1, wA.prop1, wB.prop1); // 1, 1, 5
console.log(a.doStuff(), wA.doStuff()); // 3, 45