How to get matched index of a regex for all occurences

Question

I have a string

CO12dadaCO2dafdCO345daaf

I want to extract all occurences of CO followed by some digits /CO(\d*)([\s\S]*)/, up to another CO.

In this case I want to get the output:

['CO12dada', 'CO2dafd', 'CO345daaf']

The above regex I tried also matches the rest of the CO's at once so it doesn't work.

I could get the index of a regex for the first match using str.search, but I need the indexes of a regex for all occurrences.

I need to match the that followed by anything except another match of that. — eguneys
– eguneys, Commented Sep 14, 2020 at 8:26
Using a non greedy quantifier with a positive lookahead CO[\s\S]*?(?=CO|$) regex101.com/r/VRskly/1 — The fourth bird
– The fourth bird, Commented Sep 14, 2020 at 8:28
Using Javascript, you could also shorten it to CO[^]*?(?=CO|$) — The fourth bird
– The fourth bird, Commented Sep 14, 2020 at 8:43

stranded · Accepted Answer · 2020-09-14 08:31:29Z

1

const string = 'CO12dadaCO2dafdCO345daaf'
const result = string.match(/(CO.*?)(?=CO|$)/g)
console.log(result)

answered Sep 14, 2020 at 8:31

stranded

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1 Comment

eguneys Over a year ago

I accepted this answer, because you mention the global option that solves the problem.

Ryszard Czech · Accepted Answer · 2020-09-14 20:16:38Z

1

Just get your matches with .split():

console.log("CO12dadaCO2dafdCO345daaf".split(/(?!^)(?=CO)/))

Result:

[
  "CO12dada",
  "CO2dafd",
  "CO345daaf"
]

(?!^)(?=CO) = matches the empty string before CO substring, but not at the string start.

answered Sep 14, 2020 at 20:16

Ryszard Czech

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7 Comments

eguneys Over a year ago

Cool I didn't know split took regex like that. Is that a positive lookahead, what does (?!^) do?

Ryszard Czech Over a year ago

@eguneys (?!^) is a negative lookahead, please see this question about it

eguneys Over a year ago

So split is equivalent of a match with a global regex?

eguneys Over a year ago

This is confusing, because regex doesn't match the input, but makes marks somehow (what is that mean), and in case of split those marks are split. Can you please clarify your answer.

Ryszard Czech Over a year ago

@eguneys This is out of scope, but you may want to match empty locations in a string to insert something there. "a1b2".replace(/(?=\d)/g, '-') returns a-1b-2. A must-read for you is "Lookahead and Lookbehind Zero-Length Assertions". Also, see Mastering Lookahead and Lookbehind.

|

Carsten Massmann · Accepted Answer · 2020-09-14 08:39:08Z

0

Or this one:

CO\w+?(?=CO|$)

see demo here: https://regex101.com/r/gFZomh/1

Basically: a "non-greedy" matching of all "word characters" after "CO" followed by a lookahead demanding another "CO" or end-of-string.

If you also want to match "non-word characters", you could modify the regexp to

CO[\w\W]+?(?=CO|$)

This will also work on something like "CO12dadaCO2da,fdCO345daaf" to produce the matches: ["CO12dada","CO2da,fd","CO345daaf"].

edited Sep 14, 2020 at 8:39

answered Sep 14, 2020 at 8:30

Carsten Massmann

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Comments

The fourth bird · Accepted Answer · 2020-09-14 09:22:25Z

0

Using Javascript, you can use

CO[^]*?(?=CO|$)

CO[^]*? Match CO, then any char including newlines as least as possible
(?=CO|$) Positive lookahead, assert what is on the right is either CO or the end of the string

REgex demo

answered Sep 14, 2020 at 9:22

The fourth bird

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