Created
April 15, 2019 22:29
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let regex; | |
/* matching a specific string */ | |
regex = /hello/; // looks for the string between the forward slashes (case-sensitive)... matches "hello", "hello123", "123hello123", "123hello"; doesn't match for "hell0", "Hello" | |
regex = /hello/i; // looks for the string between the forward slashes (case-insensitive)... matches "hello", "HelLo", "123HelLO" | |
regex = /hello/g; // looks for multiple occurrences of string between the forward slashes... | |
/* wildcards */ | |
regex = /h.llo/; // the "." matches any one character other than a new line character... matches "hello", "hallo" but not "h\nllo" | |
regex = /h.*llo/; // the "*" matches any character(s) zero or more times... matches "hello", "heeeeeello", "hllo", "hwarwareallo" | |
/* shorthand character classes */ | |
regex = /\d/; // matches any digit | |
regex = /\D/; // matches any non-digit | |
regex = /\w/; // matches any word character (a-z, A-Z, 0-9, _) | |
regex = /\W/; // matches any non-word character | |
regex = /\s/; // matches any white space character (\r (carriage return),\n (new line), \t (tab), \f (form feed)) | |
regex = /\S/; // matches any non-white space character | |
/* specific characters */ | |
regex = /[aeiou]/; // matches any character in square brackets | |
regex = /[ck]atherine/; // matches catherine or katherine | |
regex = /[^aeiou]/; // matches anything except the characters in square brackets | |
/* character ranges */ | |
regex = /[a-z]/; // matches all lowercase letters | |
regex = /[A-Z]/; // matches all uppercase letters | |
regex = /[e-l]/; // matches lowercase letters e to l (inclusive) | |
regex = /[F-P]/; // matches all uppercase letters F to P (inclusive) | |
regex = /[0-9]/; // matches all digits | |
regex = /[5-9]/; // matches any digit from 5 to 9 (inclusive) | |
regex = /[a-zA-Z]/; // matches all lowercase and uppercase letters | |
regex = /[^a-zA-Z]/; // matches non-letters | |
/* matching repetitions using quantifiers */ | |
regex = /(hello){4}/; // matches "hellohellohellohello" | |
regex = /hello{3}/; // matches "hellooo" and "helloooo" but not "helloo" | |
regex = /\d{3}/; // matches 3 digits ("312", "122", "111", "12312321" but not "12") | |
regex = /\d{3,7}/; // matches digits that occur between 3 and 7 times (inclusive) | |
regex = /\d{3,}/; // matches digits that occur at least 3 times | |
/* matching repetitions using star and plus */ | |
regex = /ab*c/; // matches zero or more repetitions of "b" (matches "abc", "abbbbc", "ac") | |
regex = /ab+c/; // matches one or more repetitions of "b" (matches "abc", "abbbbc", but not "ac") | |
/* matching beginning and end items */ | |
regex = /^[A-Z]\w*/; // matches "H", "Hello", but not "hey" | |
regex = /\w*s$/; // matches "cats", "dogs", "avocados", but not "javascript" | |
/* matching word boundaries | |
positions of word boundaries: | |
1. before the first character in string (if first character is a word character) | |
2. after the last character in the string, if the last character is a word character | |
3. between two characters in string, where one is a word character and the other isn't */ | |
regex = /\bmeow\b/; // matches "hey meow lol", "hey:meow:lol", but not "heymeow lol" | |
/* groups */ | |
regex = /it is (ice )?cold outside/; // matches "it is ice cold outside" and "it is cold outside" | |
regex = /it is (?:ice )?cold outside/; // same as above except it is a non-capturing group | |
regex = /do (cats) like taco \1/; // matches "do cats like taco cats" | |
regex = /do (cats) like (taco)\? do \2 \1 like you\?/; // matches "do cats like taco? do taco cats like you?" | |
//branch reset group (available in Perl, PHP, R, Delphi... commented out because this is a js file) | |
// regex = /(?|(cat)|(dog))\1/; // matches "catcat" and "dogdog" | |
/* alternative matching */ | |
regex = /i like (tacos|boba|guacamole)\./; // matches "i like tacos.", "i like boba.", and "i like guacamole." | |
/* forward reference (available in Perl, PHP, Java, Ruby, etc... commented out because this is a js file) */ | |
// regex = /(\2train|(choo))+/; // matches "choo", "choochoo", "chootrain", choochootrain", but not "train" | |
/* lookaheads */ | |
regex = /z(?=a)/; // positive lookahead... matches the "z" before the "a" in pizza" but not the first "z" | |
regex = /z(?!a)/; // negative lookahead... matches the first "z" but not the "z" before the "a" | |
/* lookbehinds */ | |
regex = /(?<=[aeiou])\w/; // positive lookbehind... matches any word character that is preceded by a vowel | |
regex = /(?<![aeiou])\w/; // negative lookbehind... matches any word character that is not preceded by a vowel | |
/* functions I find useful */ | |
regex.test("hello"); // returns true if found a match, false otherwise | |
regex.exec("hello"); // returns result array, null otherwise | |
"football".replace(/foot/,"basket"); // replaces matches with second argument |
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