i have the following string
https://www.example.com/int/de
and want to match the language code at the end of the url, eg 'de' i do that with this regex
/\..*\/.*\/([^\/?]*)\/?$/gi
I would also like to get the same result if the URL ends with a slash
But with https://www.example.com/int/de/ i only get a full match, but the group dont match 'de' anymore, although the last slash is optional in the regex
can someone the my mistake here?
分享 The mistake is not obvious, but quite a usual one: the "generic" greedy dot matching pattern followed with a series of optional subpatterns (patterns that can match an empty string).
The \..*\/.*\/([^\/?]*)\/?$ pattern matches like this: \..* matches a . and then any 0+ chars as many as possible, then backtracking starts for \/ to match a / that is the rightmost / in the string (the last one), then .*\/ matches again any 0+ chars as many as possible and then makes the engine backtrack even further and forces it to discard the previously found / and re-match the / that is before to accommodate for another rightmost / in the string. Then, finally comes ([^\/?]*)\/?$, but the previous .*\/ already matched in the URL with / at the end, and the regex index is at the string end. So, since ([^\/?]*) can match 0+ chars other than ? and / and \/? can match 0 / chars, they both match empty strings at the end of the string, and $ calls it a day and the regex engine returns a valid match with an empty value in Group 1.
Get rid of greedy dots, use a
'~([^\/?]+)\/?$~'
See the regex demo
Details
([^\/?]+) - Capturing group 1: one or more chars other than ? and /
\/? - 1 or 0 / chars$ - at the end of the string. 分享
