for和forEach绕过Array属性 [英] for and forEach bypass Array property

问题描述

我正在深入研究&对象原型（您不知道JS），我发现这件棘手的事令我震惊：

I am digging into this & Object prototype (You Don't Know JS) and I found this tricky thing that blew my mind:

我创建了一个文字数组（JS数组是对象） x = ['foo'，42，'bar'] 并添加了一个名为baz的属性，如 x.baz ='baz' 。然后，在Chrome开发者控制台中，只需键入 x 即可显示以下结果：> （3）[ foo，42， bar，baz： baz] 。如果我展开 > ，则数组的每个值都有其自己的键，例如：

I created a literal Array (JS Arrays are objects) x = ['foo', 42, 'bar'] and added a property called baz like x.baz = 'baz'. Then, in Chrome dev console, just typping x will display the following result: > (3) ["foo", 42, "bar", baz: "baz"]. If I unfold the ">", each value of the array has its own key like:

0： foo

1：42

2： bar

baz： baz

我创建了哪种 JS-object-monster ？ For和forEach循环不计算 baz 属性并忽略它。

What kind of JS-object-monster did I create? For and forEach loops do not count the baz property and bypass it.

我们将不胜感激。谢谢！

Help would be very appreciated. Thank you!

推荐答案

这不是怪物。就像其他数组一样，它只是一个JS对象。向JS数组添加属性不是不可以...可以。一个很好的理由是简单地以一种包含的方式在数组内携带状态。从功能上来说，这在像JS这样的非常松散类型的语言中是正确的。如果选择执行此操作，则还必须采取预防措施，以免被 for 循环弄糊涂。

This is not a monster. It's just a JS object like any other array. Adding properties to a JS array is not a no no... You can. One good reason is to simple carry a state in a contained manner within the array. Functionally this is correct in a very loosely typed language like JS. If you chose to do this, then you also have to take precautions in order not to be bewildered in a for in loop, for instance.

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