Select a character if some character from a list is before the character

问题

I have this regular expression:

/([a-záäéěíýóôöúüůĺľŕřčšťžňď])-$\s*/gmi

This regex selects č- from my text:

sme! a Želiezovce 2015: Spoloíč-
ne pre Európu. Oslávili aj 940.

But I want to select only - (without č) (if some character from the list [a-záäéěíýóôöúüůĺľŕřčšťžňď] is before the -).

回答1:

In other languages you would use a lookbehind

/(?<=[a-záäéěíýóôöúüůĺľŕřčšťžňď])-$\s*/gmi

This matches -$\s* only if it's preceded by one of the characters in the list.

However, Javascript doesn't have lookbehind, so the workaround is to use a capturing group for the part of the regular expression after it.

var match = /[a-záäéěíýóôöúüůĺľŕřčšťžňď](-$\s*)/gmi.match(string);

When you use this, match[1] will contain the part of the string beginning with the hyphen.

回答2:

First, in regex everything you put in parenthesis will be broken down in the matching process, so that the matches array will contain the full matching string at it's 0 position, followed by all of the regex's parenthesis from left to right.

/[a-záäéěíýóôöúüůĺľŕřčšťžňď](-)$\s*/gmi

Would have returned the following matches for you string: ["č-", "-"] so you can extract the specific data you need from your match.

Also, the $ character indicates in regex the end of the line and you are using the multiline flag, so technically this part \s* is just being ignored as nothing can appear in a line after the end of it.

The correct regex should be /[a-záäéěíýóôöúüůĺľŕřčšťžňď](-)$/gmi

来源：https://stackoverflow.com/questions/34937226/select-a-character-if-some-character-from-a-list-is-before-the-character