如何正确扩展Obect.prototype？ [英] How to extend Obect.prototype correctly?

问题描述

我正在编写一个JavaScript库，它提供了函数 tablify（任何东西）; ，它能够将任何数组或对象表示为HTML表。

I'm writing a JavaScript Library that offers the function tablify(anything);, which is able to represent any Array or Object as an HTML Table.

现在我正在尝试扩展Array和Object原型，以便像这样使用它：

Now I'm trying to extend the Array and Object prototypes in order to use it like this:

var arr = ["a", "b", "c"];
var obj = {"A": "a", "B": "b", "C": "c"};
arr.tablify();
obj.tablify();

这是我的方法：

Array.prototype.tablify = function() {
    return tablify(this);    
}
Object.defineProperty(Object.prototype, 'tablify', {
    value: function () {
        return tablify(this);
    },
    writable:     true,
    configurable: true,
    enumerable:   false
});

问题是，JavaScript中的所有内容都是对象，因此不仅仅是<$ c $这样的文字c> {a：1，b：2} 可以转换，但也可以转换其他所有内容。

The issue is, that everything in JavaScript is an Object and therefore not only literals like {a: 1, b: 2} can be converted, but also everything else.

这不会那么大处理，因为我的 tablify（）也可以处理原始类型，但当我扩展Object.prototype时，输入任何东西总是返回object，我再也无法区分类型了：

This wouldn't be such a big deal since my tablify() can also deal with primitive types, but when I extend Object.prototype, typeof anything always returns "object" and I can't distinguish between types anymore:

function tablify(object) {  
    if (object instanceof Array) {  
        return ArrayToTable(object);
    } 
    //This is always true if I extend Object.prototype: 
    if (typeof object === "object") {   //only for "normal" objects like "{a: 1, b: 2, c: [],...}"
        return ObjectToTable(object);
    }
    return PrimitiveToTable(object);    //strings, numbers, functions, ... 
}

• 为什么 typeof 总是返回object？


• 是吗？ JS-API提供这种功能是一件好事（用.tablify（）;扩展数组/对象？）？


• 如何区分正常对象，数字，函数，......？


• 是否可以只扩展普通对象？
  （禁止（42）.tablify（）; ，string.tablify（）; 。 ..）


• 这些普通物品的名称是什么？我该怎么称呼他们？


• Why is typeof always returning "object"?
• Is it a good thing for a JS-API to provide this sort of functionality (extending Arrays/Objects with ".tablify();")?
• How is it possible to distinguish between "normal" objects, numbers, functions,... ?
• Is it possible to only extend "normal" objects? (forbid (42).tablify();, "string".tablify(); ...)
• Whats the name for those "normal" objects? How should I call them?

推荐答案




为什么 typeof 总是返回object？

因为在草率模式下， 此上下文始终应该是一个对象。当您调用函数或传递undefined或null时，您将获得全局对象，当您调用方法时，上下文将被转换为对象。

Because in sloppy mode, the this context always is supposed to be an object. When you call a function or pass undefined or null, you get the global object, when you call a method the context will get casted to an object.

使用 tablify <= https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode\"rel =nofollow noreferrer>严格模式 code>方法它会起作用！

Use strict mode for your tablify method and it will work!




JS-API提供这种功能是件好事吗（使用 .tablify（）; ）扩展数组/对象？

是。 没有。。当您想要共享脚本时，许多人会皱眉使用您的脚本。有关详细讨论，请参阅为什么扩展本机对象是一种不好的做法？。

Yes. No.. Many people will frown to use your script when you want to share it. See Why is extending native objects a bad practice? for a detailed discussion.

至少你正确使用了不可枚举的属性 - 但我建议你在<$上使用它们c $ c> Array.prototype 同样，有太多人在枚举中滥用。

At least you've properly used non-enumerable properties - but I would recommend to use them on Array.prototype as well, too many people abuse for in enumerations.




如何区分普通对象，数字，函数......？

How is it possible to distinguish between "normal" objects, numbers, functions,... ?

typeof 似乎没问题。




是否可以只扩展正常 物体？ （禁止（42）.tablify（）;，string.tablify（）; ...）

Is it possible to only extend "normal" objects? (forbid (42).tablify();, "string".tablify(); ...)

不是。所有原始包装器都继承自 Object.prototype 。

Not really. All primitive wrappers inherit from Object.prototype.




这些名称是什么正常的物体？我该怎么称呼他们？

Whats the name for those "normal" objects? How should I call them?

只是对象。或者如果你想要普通对象（将它们与数组，内置函数，宿主对象区分开来）。

Just "objects". Or "plain objects" if you want (distinguishes them from arrays, built-ins, host objects).

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