javascript继承中正确的原型实现是什么？ [英] What is the correct prototype affectation in javascript inheritance?

问题描述

我已经阅读了几篇关于js继承的文章（这一篇，这一个，这个等。）

I read several articles on js inheritance already (this one, this one, this one, etc.)

在本文，经典继承如下所示:(我统一化的例子）

In this article from Mozilla, "classic" inheritance is shown as this : (I uniformized examples)

// inherit Base
function Derived() { ... }
Derived.prototype = new Base();            <-------
Derived.prototype.constructor = Derived;   <-------

但是在这篇文章我看到：

// inherit Base
function Derived() { ... }
Derived.prototype = Object.create(Base.prototype);    <-------
Derived.prototype.constructor = Derived;

此外我也看到过：

Derived.prototype = Base.prototype;

我还试验过，无法找到构造函数的使用影响：

And I also experimented and couldn't find the use of constructor affectation :

Derived.prototype.constructor = Derived; <--- it still work if I skip this line

如果我跳过此行， new Derived（）无论如何正确地调用 Derived（）。

if I skip this line, new Derived() correctly calls Derived() anyway.

所以1）什么是正确的：

So 1) what is correct :

1. Derived.prototype = new Base（）;


2. Derived.prototype = Object.create（Base.prototype）;


3. Derived.prototype = Base.prototype;


4. 其他？

1. Derived.prototype = new Base();
2. Derived.prototype = Object.create(Base.prototype);
3. Derived.prototype = Base.prototype;
4. other ?

和2）是 Derived.prototype.constructor = Derived; 真的需要吗？为什么？

And 2) is Derived.prototype.constructor = Derived; really needed ? Why ?

推荐答案

Derived.prototype = new Base();

这会调用 Base 构造函数仅用于设置原型链。虽然有时工作并给予 Object.create 等效的结果，但它容易出错，应该避免。阅读使用'new'关键字的原因是什么在Derived.prototype = new Base （以及它不的原因）。

This does call the Base constructor just for setting up the prototype chain. While sometimes working and giving equivalent results to Object.create, it is error-prone and should be avoided. Read What is the reason to use the 'new' keyword at Derived.prototype = new Base (and why it should not be used).

Derived.prototype = Object.create(Base.prototype);

这是最先进的 - 更正javascript继承这样说。

This is state of the art - Correct javascript inheritance so to say.

Derived.prototype = Base.prototype;

这是完全错误的。 不要使用。它允许 Base 和派生实例从相同的对象继承 - 而它（很少）对于类有多个构造函数可能会有所帮助，这不是子类化。

This is plain wrong. Do not use. It lets Base and Derived instances inherit from the same object - while it (seldom) can be helpful to have multiple constructors for a "class", this is not "subclassing".

派生.prototype.constructor = Derived; 真的需要吗？为什么？

Is Derived.prototype.constructor = Derived; really needed? Why?

它可以省略，但你的脚本仍然有用，但为方便起见，你会期望（ new Derived）.constructor === Derived 。另请参阅 JavaScript继承和构造函数属性

It can be omitted and your script will work nonetheless, but for convenience you would expect that (new Derived).constructor === Derived. Also have a look at JavaScript inheritance and the constructor property

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