JavaScript Regex for Path without leading or trailing slashes

Question

I'm struggling to figure out a Regex pattern for JavaScript that will trim a path of it's preceding and trailing slashes (or hashes/extensions)

For example:

path/
/path
/folder/path/
/folder/folder/path
/folder/path#hash
/folder/path.ext

Should return:

path
path
folder/path
folder/folder/path
folder/path
folder/path

I felt like I was getting close with the following, but it only selects text without any slashes, hashes, or periods.

^([^\\\/\#\.]*)(?![\#\.\\\/].*$)/gm

I'm trying to use this for Regex in a vuetify text-field validation, if that's at all helpful.

Result

I ended up with this regex slug

/^(?![\#\/\.\$\^\=\*\;\:\&\?\(\)\[\]\{\}\"\'\>\<\,\@\!\%\`\~\s])(?!.*[\#\/\.\$\^\=\*\;\:\&\?\(\)\[\]\{\}\"\'\>\<\,\@\!\%\`\~\s]$)[^\#\.\$\^\=\*\;\:\&\?\(\)\[\]\{\}\"\'\>\<\,\@\!\%\`\~\s]*$/

https://regexr.com/66ol9

Validation doesn't change the contents, it just tells you if it matches the regexp or not. — Barmar
– Barmar, Commented Oct 1, 2021 at 18:35
Correct. I just want to reject if they have a preceding or trailing slash, or hash tag, etc. — broxen
– broxen, Commented Oct 1, 2021 at 18:40

Ryszard Czech · Accepted Answer · 2021-10-01 22:03:16Z

3

This is how it is achieved with no lookbehinds (they are still rejected in Safari :():

^(?![#\/.])(?!.*[#\/.]$).*

See regex proof. And...

EXPLANATION

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    [#\/.]                   any character of: '#', '\/', '.'
--------------------------------------------------------------------------------
  )                        end of look-ahead
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    .*                       any character except \n (0 or more times
                             (matching the most amount possible))
--------------------------------------------------------------------------------
    [#\/.]                   any character of: '#', '\/', '.'
--------------------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
--------------------------------------------------------------------------------
  )                        end of look-ahead
--------------------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))

answered Oct 1, 2021 at 22:03

Ryszard Czech

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3 Comments

broxen Over a year ago

Thank you for this breakdown. I'm still capturing folder/path#hash but would like to avoid this possible case as well. I'm confused why this wouldn't be captured by the first lookahead? regex101.com/r/dYjqWQ/1

Ryszard Czech Over a year ago

@broxen To avoid strings with hash symbol, use negated character class, ^(?![#\/.])(?!.*[#\/.]$)[^#]*$. See regex101.com/r/dYjqWQ/2

broxen Over a year ago

Thank you, this did the trick.

Barmar · Accepted Answer · 2021-10-01 18:46:56Z

1

Use a negative lookahead at the beginning, and negative lookbehind at the end.

/^(?![#\/.]).*(?<![#\/.])$/

DEMO

answered Oct 1, 2021 at 18:46

Barmar

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2 Comments

broxen Over a year ago

Thank you for helping me. Unfortunately, I'm not getting the desired results. I tried your demo and regexr.com/66nk9

Barmar Over a year ago

It seems to be working at your regexr. All the paths beginning with / were rejected.

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