Object.create而不是Constructors用于继承 [英] Object.create instead of Constructors for inheritance

问题描述

我希望能够学习按照新的JavaScript ECMA 5标准创建对象，并在我当前的项目中使用它们，而不会破坏功能。但我看到让我害怕的不可解释的东西

I want to be able to learn creating Objects per the new JavaScript ECMA 5 standards, and use them in my current projects, without breaking functionality. But I see un-explainable stuff that makes me afraid

请考虑以下代码：

var foo = {
        oldProp: 'ECMA Script 3',
        newProp: 'ECMA Script 5'
    };

// The new way of inheritance
var bar = Object.create( foo );

// and of assigning properties, if I am right
var bar2 = Object.create( Object.prototype, {
        oldProp: { value: 'ECMA Script 3'},
        newProp: { value: 'ECMA Script 5'}
    });

// and then
bar; 
// console output
Object {oldProp: "ECMA Script 3", newProp: "ECMA Script 5"}

// whereas !!
bar2;
Object {} // Why this?

此外，

bar.hasOwnProperty('oldProp');  // false, whereas
bar2.hasOwnProperty('oldProp'); // true !! It should be the other way round, right? 

此外，我无法更改 bar2

bar2.oldProp = "Marry had a little lamb";
bar2.oldProp; // "ECMA Script 3"

还有更多 -

for (k in bar2) console.log(bar2[k]) // undefined  

---

我是否以正确的方式创建对象？
我基本上想要实现的是摆脱构造函数。

---

Am I creating the Objects in a correct way? What I basically want to achieve is getting rid of constructors.

旧代码：

var Slideshow = function(type) {
    this.type = type;
    this.deleteSlideshow = function() {
        // some code
    }
}
Slideshow.prototype.nextSlide = function() {
    // lotsa code
}
var vanityFairSlideshow = new Slideshow('wide-screen');

我想更改为 Object.create ，可能是这样的：

I want to change to Object.create, may be kind of this:

var Slideshow = Object.create({ /* prototype */ }, { /* properties and methods */ });
var vanityFairSlideshow = Object.create( Slideshow , { /* properties and methods */ });

这样做的正确方法是什么？

Whats the proper way of doing it?

推荐答案

这里的问题是描述符（除了值）。

Your problem here is the defaults for the descriptors (aside from value) that you omitted for each property.

使用此语法（例如 defineProperty 和 defineProperties ）， 可写 false 默认情况下， 可枚举 false 。

Using this syntax (like for defineProperty and defineProperties), writable is false by default, and enumerable is false.

将这两者设置为 true 将导致您期望的行为。

Setting both of these to true will result in the behaviour you expect.

var bar2 = Object.create( Object.prototype, {
    oldProp: { value: 'ECMA Script 3', writable: true, enumerable: true}
});

http://jsfiddle.net/YZmbg/

此外，希望您了解所有浏览器都不支持此功能;请注意 <$ c $的兼容性表C>的Object.create 。 可写和可配置属性的垫片不存在，也不存在。

Also, hopefully you appreciate how this isn't supported in all browsers; note the compatibility table for Object.create. Shims which adhere to the writable and configurable properties do not, and cannot, exist.

^{最后，+1这样一个写得很好的问题;这是一股清新的空气。}

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