英文:
Unable to access internal object after instantiation
问题
我有一个非常简单的代码，其中有已实例化的对象，我通过原型暴露了一些方法。以下是代码：
const MyClass = (function() {
function MyClass() {
this._obj = {
1: 'dfvdfvd'
};
}
function get() {
return this._obj[1];
}
MyClass.prototype.take = () => {
get.call(this);
}
return MyClass;
}());
let x = new MyClass();
console.log(x.take())
但是，我一直得到 _obj 为 undefined。我在这里漏掉了什么？
英文:
I have a very simple code with instantiated objects and I'm exposing some methods via a prototype. Here's the code:
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
const MyClass = (function() {
function MyClass() {
this._obj = {
1: 'dfvdfvd'
};
}
function get() {
return this._obj[1];
}
MyClass.prototype.take = () => {
get.call(this);
}
return MyClass;
}());
let x = new MyClass();
console.log(x.take())
<!-- end snippet -->
but I keep getting _obj as undefined. what am I missing here?
答案1
得分: 1
问题在于MyClass.prototype.take是一个箭头函数，但箭头函数没有它们自己的this（参见MDN），因此this是默认的window，而this._obj是undefined。你可以要么手动绑定它，要么像下面我所做的那样将其变成常规函数。
另外，请确保从MyClass.prototype.take()返回一个值，否则你会得到undefined。
const MyClass = (function() {
function MyClass() {
this._obj = {
1: 'dfvdfvd'
};
}
function get() {
return this._obj[1];
}
MyClass.prototype.take = function() {
return get.call(this);
}
return MyClass;
}());
let x = new MyClass();
console.log(x.take())
希望这对你有帮助。
英文:
The issue is that MyClass.prototype.take is an arrow function, but arrow functions don't have their own this (see MDN), thus this is the default window and this._obj is undefined. You can either bind it yourself, or just make it a regular function like I did below.
Also, make sure to return a value from MyClass.prototype.take(), or else you'll get undefined.
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
const MyClass = (function() {
function MyClass() {
this._obj = {
1: 'dfvdfvd'
};
}
function get() {
return this._obj[1];
}
MyClass.prototype.take = function() {
return get.call(this);
}
return MyClass;
}());
let x = new MyClass();
console.log(x.take())
<!-- end snippet -->
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