javascript - 为什么 ？函数的对象参数返回未定义的 JS

Question

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

我们正处于#lockdown状态，而我的一个兄弟padu问了这个问题。下面我有示例对象，其中有函数，同时直接调用其返回1，但分配为const并作为函数访问返回未定义。有人有任何解释将真正有助于提高我的知识。

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

戈帕尔.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())