The goal of my regular expression adventure is to create a matcher for a mechanism that could add a trailing slash to URLs, even in the presence of parameters denoted by # or ? at the end of the URL.

For any of the following URLs, I'm looking for a match for segment as follows:

1. https://example.com/what-not/segment matches segment
2. https://example.com/what-not/segment?a=b matches segment
3. https://example.com/what-not/segment#a matches segment

In case there is a match for segment, I'm going to replace it with segment/.

For any of the following URLs, there should be no match:

1. https://example.com/what-not/segment/ no match
2. https://example.com/what-not/segment/?a=b no match
3. https://example.com/what-not/segment/#a no match

because here, there is already a trailing slash.

I've tried:

1. This primitive regex and their variants: .*\/([^?#\/] ). However, with this approach, I could not make it not match when there is already a trailing slash.
2. I experimented with negative lookaheads as follows: ([^\/\#\?] )(?!(.*[\#\?].*))$. In this case, I could not get rid of any ? or # parts properly.

Thank you for your kind help!

CodePudding user response：

Lookahead and lookbehind conditionals are so powerful!

(?<=\/)[\w] (?(?=[\?\#])|$)

P.s: I just added [\w] that means [a-zA-Z0-9_] .
Of course URLs can contain many other character like - or ~ but for the examples provided it works nicely.