检查对象是否是类的“直接实例” [英] Check if object is a 'direct instance' of a class

问题描述

我有两个类：

class Bar extends Foo { // Foo isn't relevant
  constructor(value) {
    if (!(value instanceof Foo)) throw "InvalidArgumentException: (...)";
    super();
    this.value = value;
  }
}

class Baz extends Bar {
  constructor(value) {
    super(value);
  }
}

Bar 构造函数检查 value 是否是Foo的实例，如果不是，则会抛出错误。至少那是我想要的。如果您将 Bar 或 Baz 作为值传递，则if语句返回 true 。目标是只让 Foo 通过。

我发现此答案已经，但是并没有真正回答我的问题。

The Bar constructor checks if value is an instance of Foo, it throws an error if it isn't. At least, that's what I wanted it to do. If you pass a Bar or a Baz as value, the if-statement returns true as well. The goal is to only let Foos through.
I found this answer already but that didn't really answer my question.

推荐答案

检查构造函数：

if (!value || value.constructor !== Foo)
  throw 'InvalidArgumentException: (...)';

或对象的原型（这与 instanceof 确实）：

or the prototype of the object (this is more similar to what instanceof does):

if (!value || Object.getPrototypeOf(value) !== Foo.prototype)
  throw 'InvalidArgumentException: (...)';

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