什么是“未定义 x 1"?在 JavaScript 中? [英] What is "undefined x 1" in JavaScript?

问题描述

我正在根据这篇博客文章.

我正在 Google Chrome 的调试器中进行这项研究，困难的部分来了.

I am doing this research in Google Chrome's debugger and here comes the hard part.

我知道我无法删除局部变量(因为它们不是对象属性).我知道我可以从名为arguments"的数组中读出"传递给函数的所有参数.我什至知道我不能删除和数组的元素，只能实现 array[0] 的值为 undefined.

I get the fact that I can't delete local variables (since they are not object attributes). I get that I can 'read out' all of the parameters passed to a function from the array called 'arguments'. I even get it that I can't delete and array's element, only achieve to have array[0] have a value of undefined.

有人可以向我解释一下嵌入图像中 undefined x 1 的含义吗?

Can somebody explain to me what undefined x 1 means on the embedded image?

当我覆盖函数 foo 以返回 arguments[0]，然后我得到通常和正常"未定义.

And when I overwrite the function foo to return the arguments[0], then I get the usual and 'normal' undefined.

这只是一个实验，但看起来很有趣，有人知道 undefined x 1 指的是什么吗?

This is only an experiment, but seems interresting, does anybody know what undefined x 1 refers to?

推荐答案

这似乎是 Chrome 在数组(和类数组 对象)中显示未初始化索引的新方式:

That seems to be Chrome's new way of displaying uninitialized indexes in arrays (and array-like objects):

> Array(100)
[undefined × 100]

这肯定比打印 [undefined, undefined, undefined,...] 或之前的打印效果更好.

Which is certainly better than printing [undefined, undefined, undefined,...] or however it was before.

虽然，如果只有一个 undefined 值，他们可以删除 x 1.

Although, if there is only one undefined value, they could drop the x 1.

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