Regex lookahead AND lookbehind

Question

I want to replace all ® signs on my website to an ® with JavaScript. But I have to care that I only replace them if there is no sup surrounding them already (maybe from CMS users).

I already tried the following but it does not work fine.

html.replace(/(?<!.{0,})®(?!.{0,}<\/sup>)/g, "®")

It does only care for the  Tag and does not work in Safari cause of an "invalid group specifier name". Maybe someone here can help me with this.

You need [this technique](https://stackoverflow.com/a/641432/3832970) that was [expanded here](https://stackoverflow.com/a/35143111/3832970). — Wiktor Stribiżew, Mar 04 '22 at 09:31

score 1 · Accepted Answer · answered Mar 04 '22 at 09:34

You could use a regex replace with an alternation and callback:

var input = "Hello ® and also <sup>®</sup>";
var output = input.replace(/<sup>®<\/sup>|®/g, (x) => x === "<sup>®</sup>" ? x : "<sup>®</sup>");
console.log(output);

The alternation logic first eagerly attempts to find ® occurrences. That failing, it also tries to find any other ® occurrence. Then, in the callback, we wrap with  tags only if not already wrapped.

Thanks for your help! Super easy solution for my problem. – aagJohn Mar 07 '22 at 06:41 — aagJohn, Mar 07 '22 at 06:41

Regex lookahead AND lookbehind

1 Answers1