regexpのdebugging

https://www.debuggex.com/

Non caputring group (aka: question mark colon)

()でgroupはするけどcaptureされないことをnon-capturing groupと言う。

?:

• http://stackoverflow.com/questions/3512471/non-capturing-group
• http://stackoverflow.com/questions/3512471/what-is-a-non-capturing-group

non-capturing groupを利用したcapturing

• http://stackoverflow.com/questions/18402416/regular-expression-to-match-a-whole-word

このように書くと

[s|season]

s,e,a,o,nがcaptureされる(Square brackets are meant for character class, and you're actually trying to match any one of: s, |, s (again), e, a, s (again), o and n.)

これを避けるためにはgroupingを利用する (Use brackets instead for grouping:)

(s|season)

もし、captureはするけど利用しないなら non-capturing groupにする (or non-capturing group:)

(?:s|season)