正则表达式匹配单个新行。正则表达式匹配双新线 [英] Regex to match single new line. Regex to match double new line

问题描述

我正在尝试构建一个匹配单独换行符（ \ n ）的正则表达式。

I am trying to construct a regex that will match a solitary newline character (\n).

同样，我需要另一个正则表达式来匹配不属于的双重换行符（ \ n \ n ）较长的换行符字符，例如 \ n \ n \ n 或 \ n \ nn \ n \ n \\ n \\ n 等。

Similarly, I need another regex to match double newlines (\n\n) that are not part of a longer run of newline characters like \n\n\n or \n\n\n\n\n\n etc.

\ n（？！\ n）和 \ n \ n（？！\ n）匹配太多（它们与较长的换行序列中的最后一个换行符匹配）。我该怎么办？

\n(?!\n) and \n\n(?!\n) match too much (they match the last newline(s) in a longer sequence of newlines). What can I do instead?

推荐答案

由于JavaScript不支持lookbehind断言，因此您需要匹配一个额外的字符在你的 \ 之前，记得稍后处理它（即，如果你使用正则表达式匹配来修改原始字符串，则恢复它）。 / p>

Since JavaScript doesn't support lookbehind assertions, you need to match one additional character before your \n`s and remember to deal with it later (i.e., restore it if you use the regex match to modify the original string).

(^|[^\n])\n(?!\n)

匹配单个换行符加上前一个字符，

(^|[^\n])\n{2}(?!\n)

匹配双换行加上前一个字符。

matches double newlines plus the preceding character.

所以如果你想要替换一个 \ n 使用< br /> ，例如，你必须这样做

So if you want to replace a single \n with a <br />, for example, you have to do

result = subject.replace(/(^|[^\n])\n(?!\n)/g, "$1<br />");

对于 \ n \ n ，它是

result = subject.replace(/(^|[^\n])\n{2}(?!\n)/g, "$1<br />");

在上查看regex101

说明：

(       # Match and capture in group number 1:
 ^      # Either the start of the string
|       # or
 [^\n]  # any character except newline.
)       # End of group 1. This submatch will be saved in $1.
\n{2}   # Now match two newlines.
(?!\n)  # Assert that the next character is not a newline.

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