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🎰 Regular Expressions

Various useful tools and resources for working with regular expressions.

ðŸ’Ą Tips​

  • Think about you want to "match" or "search"
  • For matching, use ^ and $ to match the beginning and end of the string
    • Be careful with multi-line strings
  • Different tools may have different syntax

Characters​

CharacterRegExNotes
Lowercase letter[a-z]
Uppercase letter[A-Z]
Letter[a-zA-Z]
Digit\dEqual to [0-9]
Non-digit\D
Whitespace\sCould be space, tab, etc.
Non-whitespace\S
Word character\wEqual to [a-zA-Z0-9_]
Non-word\W
Word boundary\b
Non-boundary\B

Quantifiers​

note

In possessive match mode, the regex engine will not backtrack to find a match. This is useful when you know that there is only one possible match. This can be more efficient than greedy or reluctant matching, but more prone to not finding a match.

QuantifiersRegExNotes
More or 0*Greedy Match (Prefer more)
More or 1+Greedy Match (Prefer more)
1 or 0?Greedy Match (Prefer one)
0 or more*?Reluctant Match (Prefer 0)
1 or more+?Reluctant Match (Prefer 1)
0 or 1??Reluctant Match (Prefer 0)
0 or more*+Possessive Match
1 or more++Possessive Match
1 or 0?+Possessive Match
Exactly n{n}, {n}+, {n}?
At least n{n,}Greedy Match (Prefer more)
Between n and m{n,m}Greedy Match (Prefer more)
At least n{n,}?Reluctant Match (Prefer less)
Between n and m{n,m}?Reluctant Match (Prefer less)
At least n{n,}+Possessive Match
Between n and m{n,m}+Possessive Match

Tools​

Snippets​

Email​

TODO

URL​

TODO

Private IP Address1​

StartEndCIDR
127.0.0.0127.255.255.255127.0.0.0/8
10.0.0.010.255.255.25510.0.0.0/8
172.16.0.0172. 31.255.255172.16.0.0/12
192.168.0.0192.168.255.255192.168.0.0/16
(^127\.)|
(^10\.)|
(^172\.1[6-9]\.)|(^172\.2[0-9]\.)|(^172\.3[0-1]\.)|
(^192\.168\.)

Base64 encoded string​

^[a-zA-Z0-9+/]*={0,2}$

URL-safe slug​

  • Have at least one character
  • Contains only letters, numbers, hyphens, and underscores
  • Does not start or end with a hyphen or underscore
  • Does not have consecutive hyphens or underscores
^[a-zA-Z0-9]+([-_][a-zA-Z0-9]+)*$

Semantic Version​

^(\d+)\.(\d+)\.(\d+)$

Chinese Characters​

[\u4e00-\u9fa5]

ðŸ‡đ🇞 Taiwan Address​

This is a WIP, might not be perfect.

^[\u4e00-\u9fa5]+?(įļĢ|åļ‚)[\u4e00-\u9fa5]+?(鄉|éŽŪ|åļ‚|區)[\u4e00-\u9fa5]+?(č·Ŋ|街|åĪ§é“)([\u4e00-\u9fa5]+?æŪĩ)?(\d+?å··)?(\d+?åž„)?[\d\-、]+?號(.+?æĢŸ)?((B?[\d]+?|G|L)æĻ“)?(äđ‹\d+?)?$

ðŸ‡đ🇞 Taiwan Address with Village​

^[\u4e00-\u9fa5]+?(įļĢ|åļ‚)[\u4e00-\u9fa5]+?(鄉|éŽŪ|åļ‚|區)([\u4e00-\u9fa5]+?(村|里))?(\d+?鄰)?[\u4e00-\u9fa5]+?(č·Ŋ|街|åĪ§é“)([\u4e00-\u9fa5]+?æŪĩ)?(\d+?å··)?(\d+?åž„)?[\d\-、]+?號(.+?æĢŸ)?((B?[\d]+?|G|L)æĻ“)?(äđ‹\d+?)?$

References​

Footnotes​

  1. https://stackoverflow.com/a/2814102/10325430 â†Đ