为什么 ？函数的对象参数 returns undefined JS

Question

In this query, i've have small doubt i need to know WHY?

我们正处于#lockdown 意味着我的一个兄弟 padu 问了这个问题。下面我有示例对象，因为在直接调用其 return 1 时有函数，但在分配为 const 和访问时作为函数 returns 未定义。哪位大神解释一下，对我的知识增长很有帮助。

const apple = 3;
const data = {
  apple: 2,
  bag: {
    apple: 1,
    plastic: function(){
      return this.apple;
    }
  }
}
const plastic = data.bag.plastic;
console.log(plastic())             **//Result - undefined**
console.log(data.bag.plastic())    **//Result - 1**

谢谢，

Gopal.R

Answer 1

您正在搜索 bind()

const apple = 3;
const data = {
  apple: 2,
  bag: {
    apple: 1,
    plastic: function(){
      return this.apple;
    }
  }
}
const plastic = data.bag.plastic.bind(data.bag);
console.log(plastic())           
console.log(data.bag.plastic())