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Regex Cheatsheet

Awesome regex cheatsheet I found online. Often, I find myself re-learning regex syntax because I don’t use it often.

/hello/looks for the string between the forward slashes (case-sensitive)
/hello/ilooks for the string between the forward slashes (case-insensitive)
/hello/glooks for multiple occurrences of string between the forward slashes
/h.llo/the ‘.’ matches any one character other than a new line character… matches ‘hello’, ‘hallo’ but not ‘h llo’
/h.*llo/the “*” matches any character(s) zero or more times… matches “hello”, “heeeeeello”, “hllo”, “hwarwareallo”
/\d/matches any digit
/\D/matches any non-digit
/\w/matches any word character (a-z, A-Z, 0-9, _)
/\W/matches any non-word character
/\s/matches any white space character (\r (carriage return),\n (new line), \t (tab), \f (form feed))
/\S/matches any non-white space character
/[abcd]/matches any character in square brackets
/[ch]at/matches cat or hat
/[^abcd]/matches anything except the characters in square brackets
/[a-z]/matches all lowercase letters (a to z)
/[A-Z]/matches all uppercase letters (A to Z)
/[0-9]/matches all digits
/[a-zA-Z]/matches all lowercase and uppercase letters
/[^a-zA-Z]/matches non-letters
/[a-zA-Z0-9]/matches all lowercase, uppercase letters and numbers
/(hello){4}/matches “hellohellohellohello”
/hello{3}/matches “hellooo” and “helloooo” but not “helloo”
/(hello){1,3}/matches “hello” that occur between 1 and 3 times (inclusive)
/(hello){3,}/matches “hello” that occur atleast 3 times
/ab*c/matches zero or more repetitions of “b” (matches “abc”, “abbbbc”, “ac”)
/ab+c/matches one or more repetitions of “b” (matches “abc”, “abbbbc”, but not “ac”)
/^/matches beginning of a line
/$/matches end of a line
/(hard)?work/matches “work” or “hardwork”
/(?:hard)?work/matches “work” or “hardwork” but is a non-capturing group
/i am a (cat|dog|whale) person/matches “i am a cat person”, “i am a dog person” and “i am a whale person”
/z(?=a)/positive lookahead… matches the “z” before the “a” in pizza but not the first “z”
/z(?!a)/negative lookahead… matches the first “z” but not the “z” before the “a”
/(?<=[aeiou])\w/positive lookbehind… matches any word character that is preceded by a vowel
/(?<![aeiou])\w/negative lookbehind… matches any word character that is not preceded by a vowel

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