Javascript新的Array和join()方法 [英] Javascript new Array and join() method

问题描述

受到这篇流行演讲的启发，我想找出一些与创建数组有关的问题.假设我正在使用以下方法创建新数组:

Inspired by this popular speech I wanted to figure out some issue related to creating arrays. Let's say I am creating new array with:

Array(3)

在控制台中，我得到:

[未定义，未定义，未定义]

这很明显.假设我正在加入该数组:

Which is pretty obvious. Let's say I am doing joining on that array:

Array(3).join()

作为回应，我得到了:

",,"

这也是可以理解的，因为我想这是三个用逗号分隔的空字符串.但是当我尝试做的时候:

Which is pretty understandable as well, because these are three empty strings, separated by commas, I suppose. But when I am trying to do:

Array(3).join("lorem")

我得到的字符串只有两个重复的"lorem":

I am getting string with only two repeat of "lorem":

"loremlorem"

为什么这个单词有两个而不是三个重复?

Why there are two, not three repeats of that word?

推荐答案

join 使用作为联接程序传递的内容将元素联接在一起.因此，您有三个空字符串环绕" lorem s:

join joins the elements together, using what was passed as a joiner. So you have three empty strings "surrounding" the lorems:

|lorem|lorem|

如果不使用空数组，可能会更加明显:

It might be a little more obvious if you don't use an empty array:

var arr = [1, 2, 3, 4, 5]; // Like Array(5), except not sparse

arr.join('-and-'); // 1-and-2-and-3-and-4-and-5

顺便说一句，您的第一个示例 join 输出是不正确的.它应该是，或，" .(取决于输出格式.)

And your first example join output, by the way, is incorrect. It should be ,, or ",,". (Depends on the output format.)

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