Javascript regex to emulate css 'double bar' combinator

Asked Sep 18 '18 at 07:40

Active Sep 18 '18 at 08:36

Viewed 63 times

I'm looking for a regex that works in Javascript and emulates the double bar combinator for css rules.

The way double bar works:

I found this answer which works perfectly except it doesn't work in Javascript

I spent a while trying to reformulate it to make it work in Javascript but I haven't had any luck.

^(?:(?:(?!\1)()|\1 )(?:(?!\2)()fat|(?!\3)()cat)){1,2}$

Here is a link to the regex (Python) that shows it working as intended

Here is a link to the same regex to show it doesn't work in Javascript

edited Sep 18 '18 at 08:36

asked Sep 18 '18 at 07:40

tleef

It is a known difference. JS regexp engine initializes all captures with an empty string while Python `re` keeps them as `null`. – Wiktor Stribiżew Sep 18 '18 at 07:44
Is there any way to do the same achieve the same effect in JS? – tleef Sep 18 '18 at 07:45
Are you planning to create the pattern dynamically? – Wiktor Stribiżew Sep 18 '18 at 07:49
Yeah, I'm creating the regex programatically. Additionally, fat and cat will themselves be more complicated regexes to match css values – tleef Sep 18 '18 at 07:55
This pattern works well for two terms but it is not expandable to 3+ terms https://regex101.com/r/8GFcTs/2 – tleef Sep 18 '18 at 08:28
Sorry it wasn't clear but each word can only appear at most once. I updated the question – tleef Sep 18 '18 at 08:34
Why use regex if you just may split with spaces, check if all the values are in your list? – Wiktor Stribiżew Sep 18 '18 at 08:44

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