javascript regex split 产生太多项目 [英] javascript regex split produces too many items

问题描述

我正在尝试使用逗号或空格分割字符串.逗号可以选择性地前面和/或后面跟空格，空格本身也算作分隔符.代码如下所示:

I'm trying to split a string using either commas or whitespace. A comma can optionally be preceded and/or followed by whitespace, and whitespace by itself also counts as a delimiter. The code looks like this:

var answers= s.split(/(s*,s*)|s+/);

如果 s 包含字符串 'a b,c'，我会得到一个包含五个项目的列表(数组)，而不是预期的三个:

If s contains the string 'a b,c', I get a list (array) containing five items instead of the expected three:

0:a, 1:undefined, 2:b, 3:,, 4:c

0:a, 1:undefined, 2:b, 3:,, 4:c

任何关于我做错了什么的建议将不胜感激.

Any advice as to what I'm doing wrong will be appreciated.

菲利普

推荐答案

那是因为 split 也推送 捕获组到结果数组:

That's because split does also push capturing groups to the result array:

如果separator是一个包含捕获括号的正则表达式，那么每次separator匹配时，捕获括号的结果(包括任何未定义的结果)都会拼接到输出数组中.

If separator is a regular expression that contains capturing parentheses, then each time separator is matched the results (including any undefined results) of the capturing parentheses are spliced into the output array.

a 和 b 之间的空格与空格匹配，因此捕获组未定义.b 和 c 之间的逗号被组匹配，所以它成为你数组的第四项.

The space between a and b was matched by the whitespace, so the capturing group was undefined. The comma between b and c was matched by the group, so it became the fourth item of your array.

要解决这个问题，只需删除捕获组:

To solve the issue, just remove the capturing group:

var answers = s.split(/s*,s*|s+/);

如果你有一个更复杂的表达式需要分组，你可以像这样让它不捕获:

If you had a more complex expression where you needed grouping, you could make it non-capturing like this:

var answers = s.split(/(?:s*,s*)|s+/);

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