javascript原型继承混淆 [英] javascript prototypical inheritance confused

问题描述

给出实现这种继承的标准方法

given the standard way of achieving inheritance like this

function BaseClass() {

}

function SubClass() {
    BaseClass.call(this);
}

SubClass.prototype = Object.create(BaseClass.prototype);
SubClass.prototype.constructor = SubClass;

为什么需要这样做

SubClass.prototype = Object.create(BaseClass.prototype);

并最终得到类似

function F(){}
F.prototype = BaseClass.prototype;
SubClass.prototype = new F();

而不是只做

Subclass.prototype = BaseClass.prototype;

推荐答案

为JavaScript中的事物赋值实际上只是复制引用（除非使用基本类型）。所以当你这样做时：

Assigning values to things in JavaScript really just copies a reference (unless working with primitive types). So when you do this:

Subclass.prototype = BaseClass.prototype;

你真正做的是分配<$ c的原型$ c> SubClass 到内存中与 BaseClass 原型相同的位置，因此您对所做的任何原型相关更改SubClass 也会影响 BaseClass 。这是一个小例子：

What you're really doing is assigning the prototype of SubClass to the same location in memory as the prototype of BaseClass, therefore any prototype related changes you make to SubClass will also affect BaseClass. Here's a little example:

function BaseClass() {

}

function SubClass() {
    BaseClass.call(this);
}

SubClass.prototype = BaseClass.prototype;
SubClass.prototype.constructor = SubClass;

SubClass.prototype.subClassFunction = function(){
    console.log("Added this to SubClass");
}

var baseObj = new BaseClass();
baseObj.subClassFunction(); // => "Added this to SubClass"

---

这就是你想要的原因使用

---

That's why you want to use

SubClass.prototype = Object.create(BaseClass.prototype);

因为它会创建 new 和 unique 使用指定原型的对象。

because it will create a new and unique object with the specified prototype instead.

您可以阅读有关此函数如何工作的更多信息 here 。

You can read more about how this function works here.

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