困惑关于道格拉斯Crockford的对象函数 [英] Confused about Douglas Crockford's object function

问题描述

我知道Crockford在JavaScript中有一个着名的对象函数用于继承：

I know Crockford has a famous object function for inheritance in JavaScript:

function object(o) {
    function F() {}
    F.prototype = o;
    return new F();
}

但我很困惑，行后 prototype = o ，为什么他不重置 F.prototype 的构造函数，如下所示：

But I am confused, after the line F.prototype = o, why he doesn't he reset the F.prototype's constructor, like this:

F.prototype.constructor = F

这不是常见的做法吗？ / p>

Isn't that common practice?

推荐答案

这不是常见的做法吗？

Isn't that common practice?

只有当你创建子类（构造函数，原型继承自其他原型）。

Only when your're creating subclasses (constructor functions with prototypes inheriting from other prototypes).

但这不是目的此代码基本上 Object.create 。它需要创建从另一个对象继承的对象的一部分，没有别的。 F 构造函数只是中间的，不应该被暴露。

But that's not the purpose of this code, which basically Object.create. It takes the part of creating the object which inherits from another object, nothing else. The F constructor function is only intermediate and not supposed to be exposed.

F.prototype = o;

为什么他不做 F.prototype.constructor = F ？

why he doesn't he do F.prototype.constructor = F?

因为这会改变 o 目的只是创建一个新对象。请注意，它会返回中间构造函数的实例，而不是构造函数本身。

Because that would change o itself. The aim is only to create a new object. Notice that it returns an instance of the intermediate constructor, not the constructor itself.

将构造函数设置（如果需要）？在由对象实例化的新对象上：

Where would the constructor be set (if needed)? On the new object that is instantiated by object:

 function inherit(chd, par) {
     chd.prototype = object(par.prototype);
     chd.prototype.constructor = chd;
 }

 function Foo() {}
 function Bar() {}
 inherit(Foo, Bar);

 /* Because of overwriting `constructor`: */
 Foo.prototype.constructor === Foo
 (new Foo).constructor === Foo

 /* Because of the prototype chain: */
 new Foo instanceof Bar // true, because
 Foo.prototype instanceof Bar // true

这篇关于困惑关于道格拉斯Crockford的对象函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！