matching regex for custom params in URI

Question

I am building a web framework and REGEX is really hostile today.
I do not like the django way of formatting custom params with angle brackets

url/<param>/... or
<str:token>/

I would prefer the way js and other programs handle this

name/:token/:another_param

After trying for 45 minutes I am giving up. I would like to allow only characters like a-zA-Z0-9_:/. The main issue here is that I do not want to allow recursive colons like this

:::id

These are strings I would like to match

empty string (although I could check prior matching)
/
:id
/:id
/:id/
person/:name/:id/:token_person2/image
person////
////

Could someone help me?

Asked By: Alex D'ago

||

Source

Answer 1

You don’t want to match :: and apparently also not :/

What you can do is use a single negative lookahead to assert that those 2 strings do not occur.

^(?![/w:]*:[:/])[/w:]*$

Explanation

^ Start of string
(?![/w:]*:[:/]) Negative lookahead, assert not :: or :/ to the right
[/w:]* Optionally repeat matching one of /, w (word character) or :
$ End of string

const regex = /^(?![/w:]*:[:/])[/w:]*$/;
[
  "",
  "/",
  ":id",
  "/:id",
  "/:id/",
  "person/:name/:id/:token_person2/image",
  "person////",
  "////",
  ":::id",
  "person/:/name",
].forEach(s =>
  console.log((regex.test(s) ? "" : "No ") + `Match --> '${s}'`)
)

See a regex demo

Answered By: The fourth bird

matching regex for custom params in URI

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