Javascript regex grouping question

Question

I want to be able to detect/pick apart strings like :

tickets at entrance per person
ballons pp
tree planting

i.e. a description followed by an optional "pp" or "per person"

I try (.+)\s+(per person|pp) and that works; but the pp|per person suffix is then not optional.

I try (.+)\s+(per person|pp)? or (.+)\s+(per person|pp){0,1} to make it optional, but then I get "undefined for the second capture group". Curiously the first capture group contains the "per":

matches: 0: (tickets at entrance per )
1: (tickets at entrance per)
2: (undefined)

(tested via http://www.regextester.com/ online regex tester)

What am I doing wrong with that second capture group ?

Colin Hebert · Accepted Answer · 2010-09-23 21:45:18Z

1

You can try this :

^(.+?)\s*(per person|pp|)$

You can read it like this :

Starts with  
 (any characters but at least one and not in greedy mode)
 any space-characters
 ("per person" or "pp" or nothing)
end

edited Sep 23, 2010 at 21:45

answered Sep 23, 2010 at 20:21

Colin Hebert

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3 Comments

user456613 Over a year ago

Turns out this isn't quite what is needed after all. The required "any space character" in the middle there wont be present when the string does not contain the "pp|per person" suffix.

user456613 Over a year ago

I spoke too soon. I had tried ^(.+)\s+(per person|pp|)$ which does work (note the \s+ vs the suggested \s*), but requires a trailing space if the per person|pp is not the suffix So for example: "tree planting" will not be matched by this regex, although "tree planting " (note the trailing space) will be. The regex you suggested: ^(.+)\s*(per person|pp|)$ Does not work because the first group is greedy and returns the whole string, eg. "balloons per person" returns 1: (balloons per person) 2: () instead of what I want which is: 1: (balloons) 2: (per person)

Colin Hebert Over a year ago

Updated with an ungreedy "+" :)

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