懒惰的吸气剂在课堂上不起作用 [英] Lazy getter doesn't work in classes

问题描述

class a {
    get b() {
        delete this.b;
        return this.b = 1;
    }
}

var c = {
    get b() {
        delete this.b;
        return this.b = 1;
    }
}

console.log(c.b); // works as expected
console.log((new a()).b); // throws error

上面的代码应该可以正常工作，但是最后一行会抛出.

The above code should work fine but the last line throws.

未捕获的TypeError:无法设置仅具有吸气剂(...)的#的属​​性b

Uncaught TypeError: Cannot set property b of # which has only a getter(…)

很明显，在类中没有删除吸气剂，而在对象中却可以正常工作.我正在使用最新的稳定铬.

Clearly the getter is not being deleted in class whereas it works fine in object. I am on latest stable chrome.

惰性Getter MDN条目

推荐答案

该类的获取器位于.prototype对象上，而不是在this上，这就是您尝试delete失败的原因(并且杰里米指出，它不可删除.

The getter of the class sits on the .prototype object, not on this, that's why your attempt to delete it fails (and, as Jeremy points out, it is not deletable).

不过，您可以简单在遮盖吸气剂的实例上创建自己的属性:

You can however simply create an own property on the instance that shadows the getter:

class a {
    get b() {
        Object.defineProperty(this, "b", { value: 1, writable: false, configurable: true })
        return this.b;
    }
}

var c = new a;
console.log(c.b); // 1

我们必须使用 Object.defineProperty() 作为一个简单的赋值，将发现没有setter和throws的继承属性.

We have to use Object.defineProperty() as a simple assignment would find the inherited property that has no setter and throws.

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