使用Object.create(null)创建对象时__proto__如何工作 [英] How does __proto__ work when object is created with Object.create(null)

问题描述

考虑以下javascript代码

Consider the following javascript code

var a = Object.create(null);
a.foo = 1;
var b = Object.create(a);
console.log(b.foo);  //prints 1
console.log(b.__proto__);  //prints undefined
b.__proto__ = null;
console.log(b.__proto__);  //prints null
console.log(b.foo);  //prints 1

有人能解释即使将 b .__ proto __ 设置为null之后，对象 b 如何访问 a 的"foo"属性吗?用于访问 a 的属性的内部链接是什么?

Can anyone explain how object b is accessing the "foo" property of a even after setting b.__proto__ to null? What is the internal link which is used to access the property of a?

我尝试在SO中搜索可能的解释，但找不到关于Java特定行为的任何解释.

I tried searching through SO for possible explanations but couldn't find any explanation for this particular behaviour of Javascript.

推荐答案

您的问题是您正在使用已弃用 __ proto __ 属性，它是 Object.prototype 上的吸气剂/设置器-但是您的对象不会继承该对象，因此首先是 undefined ，赋值会创建一个标准属性名称为 __ proto __ .

Your problem is that you are using the deprecated __proto__ property, which is a getter/setter on Object.prototype - but your objects don't inherit from that, so it's undefined at first and the assignment creates a standard property with the name __proto__.

使用正确的 Object.getPrototypeOf />代替code> Object.setPrototypeOf ，代码将完成您期望的操作:

Use the proper Object.getPrototypeOf/Object.setPrototypeOf instead and the code will do what you expect:

var a = Object.create(null);
a.foo = 1;
var b = Object.create(a);
console.log(b.foo); // 1
console.log(Object.getPrototypeOf(b)); // {foo:1} - a
Object.setPrototypeOf(b, null);
console.log(Object.getPrototypeOf(b)); // null
console.log(b.foo); // undefined

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