Backreference non capture group in javascript regex

Question

This is going to be a really short question...

Lets assume I have a regex like:

(Hello)(?:fooBar)

How can I backreference it using \2? I know this works with normal capturing groups and that a non capturing group only groups tokens together but if there is any work-around then I would be glad to know.

Edit: Problem is:

I need to backreference to non capturing groups sometimes. For example there are moments where I really dont want that group to show up as a match but it shows up multiple times in the pattern which is why I prefer to backreference it.

Try adding a second empty capturing group - (Hello)(?:fooBar)(). Or an outer group: ((Hello)(?:fooBar)). Or ((Hello))(?:fooBar), (Hello)((?:fooBar)), etc. What are you trying to achieve? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jan 23, 2017 at 8:21
@WiktorStribiżew didnt know this question was bad quality. Isnt it clear what im asking? — Asperger
– Asperger, Commented Jan 23, 2017 at 8:23
What are you asking for? What is the real problem? Please clarify. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jan 23, 2017 at 8:25
That is not possible to backreference a non-capturing group as it does not create any memory buffers with the captured texts. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jan 23, 2017 at 8:29
@WiktorStribiżew ya, I thought so, that is really unfortunate but oh well. At least my doubts are gone now xD. — Asperger
– Asperger, Commented Jan 23, 2017 at 8:30

Ray Toal · Accepted Answer · 2017-01-23 08:37:10Z

2

As mentioned in the comments, a backreference applies only to a capture group.

But it sounds like your actual concern is with not repeating yourself. In this case, you can construct the regex:

const f = 'foobar';
const r = new RegExp(`Hello${f}blah${f}blah${f}blah`);

answered Jan 23, 2017 at 8:37

Ray Toal

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1 Comment

Asperger Over a year ago

Actually you are right. It should have crossed my mind. I hardly used the regex object.

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