Regex negative lookbehind replace in JavaScript

Question

I have a JS regex with a negative lookbehind assertion that works fine in Chromium-based browsers:

(?<!https?:)\/\/(.+?)(?<!https?:)\/\/gmi

I need to replace it to another for cross browser compatibility (won't work in FF or Safari).

Regex means "Find and capture all occurrence inside slashes // //, except if before // stay http: or https:".

Example:

bar //foo bar// foo - match (capture //foo bar//)
//https://stackoverflow.com/// - match (capture https://stackoverflow.com/)
https://stackoverflow.com// - not match
//foo http://stackoverflow.com - not match

Live Demo

As @BaliBalo said, my current regex contains error and work not perfectly Error Demo I need capture https://stackoverflow.com/ in //https://stackoverflow.com///

The second line would capture `https://stackoverflow.com` without the trailing slach, right? — Bali Balo, Jul 04 '19 at 18:19
@BaliBalo no, with trailing slash (like in example, need capture https://stackoverflow.com/ ) — John Doe, Jul 04 '19 at 18:23
@JohnDoe your current regex with lookbehinds doesn't: https://regex101.com/r/mU5rR8/19 — Bali Balo, Jul 04 '19 at 18:25
@sln it's possible,cause i saw example,that work. But,unfortunately,code was obfuscated — John Doe, Jul 04 '19 at 18:25
@BaliBalo so,my regex contains error...thanks for attentiveness! — John Doe, Jul 04 '19 at 18:30
@sln it can be done with temporary cut links to exclude interceptions,incorrect captures and simplifications regex,but it highly unwanted. — John Doe, Jul 04 '19 at 18:59

score 0 · Answer 1 · answered Jul 04 '19 at 18:24

If you only want to use them in a replace, you can try the opposite. Also capture what you don't want if it's there, and if that's the case just ignore the match. This behaves slightly differently in some edge cases but is acceptable in most situations.

Your regex could for example be:

let result = input.replace(/(https?:)?\/\/((?:https?:\/\/|.)+?)\/\//g, (m, e1, val) => e1 ? m : '[match](' + val + ')');

Regex negative lookbehind replace in JavaScript

1 Answers1