CODEWITHSUNDEEP
regex
ncFoCo
ncFoCo

Reputation: 35

RegEx capture group that excludes a specific pattern

I am trying to come up with a RegEx pattern that takes strings that look like this: 

KEEP_THIS_L_1234  
KEEP_THIS_R_12  
KEEP_THIS

and returns a capture group with this result: 

KEEP_THIS
KEEP_THIS
KEEP_THIS

So far I have tried /^(\w+)(?=_(L|R))(?=_\d{0,4})/, but this pattern only returns the capture groups for the first two instances: 

KEEP_THIS
KEEP_THIS

Can someone help me understand what I am missing?

Thanks!

Upvotes: 0

Views: 50

Answers (2)

toddmo
toddmo

Reputation: 22466

you need to make the last two groups optional, like this:

/^(\w+?)((_(L|R))(_\d{0,4}))?$/

Your desired result will always be in $1.

This has the advantage that your other data captured (if any) will be in groups $2 and $3.

Upvotes: 1

Avinash Raj
Avinash Raj

Reputation: 174834

Change your regex like below.

^(\w+)(?=(?:_[LR]_\d{0,4})|$)

DEMO

Upvotes: 0

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