Object内部箭头函数的值 [英] Value of this inside arrow function inside an Object

问题描述

我以为我理解这个和箭头函数之间的关系，但是下面的代码片段让我质疑我的理解。

I thought I understood the relationship between this and arrow functions but the following snippet is making me question my understanding.

let person = {
  name: 'Jim',
  sayName: () => {
    console.log(this.name);
  }
};

person.sayName();

我知道箭头函数捕获这个封闭上下文的值。我原以为这个将是对象，而是 Window 。

I understand that arrow functions capture the this value of the enclosing context. I was expecting this would be the object but instead it is Window.

有人可以帮我理解为什么会这样吗？

Can someone help me understand why this is the case?

推荐答案

您对箭头功能的理解大多是正确的：箭头函数有一个词汇 this ，它在箭头函数中的值由周围的范围决定。

Your understanding of arrow functions is mostly correct: Arrow functions have a lexical this and its value within the arrow function is determined by the surrounding scope.

你可能假设此在 person 对象文字中获得不同的值。 事实并非如此。

You probably assume that this gets a different value within the person object literal. This is not the case.

因此，让我们看看这个在您的（全局）范围内引用的内容：

So let's see what this refers to in your (global) scope:

console.log(this === window); // true

let person = {
  name: 'Jim',
  test: console.log(this === window), // true
  sayName: () => {
    console.log(this === window); // true
  }
};

person.sayName();

As你可以看到，当创建分配给 sayName 的箭头功能时，这个指的是窗口对象。

As you can see, when the arrow function assigned to sayName is created, this refers to the window object.

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