Cheatography
https://cheatography.com
Anchors (boundaries)^ | Start of string or line | $ | End of string or line | \A | Start of input (ignores 'm' flag) | \Z | End of input (ignores 'm' flag) | \G | End of the previous match | \b | Word boundary (any position proceeded or followed - but not both - by a letter, digit or underscore) | \B | Non-word boundary |
Character and Sets\w | Word | [a-zA-Z0-9_] | \W | Non-word | [^a-zA-Z0-9_] | \d | Digit | [0-9] | \D | Non-digit | \s | Whitespace (Form-feed, tab, vertical-tab, new line, carriage return and space) | [\f\t\x0b\n\r ] | \S | Non-whitespace | \x | Hexadecimal digit | \x00=null; \x0d=\r; [\x61-\x7a]=[a-z] | \O | Octal digit | . | Any character (except new line \n) |
Groups(...) | Capture group - captures a set of characters for a later expression | (?:...) | Non-capture group - groups an expression but does not capture. e.g. /((?:foo|fu)bar)/ matches "foobar" or "fubar" without "foo" or "fu" appearing as a captured subpattern | (?=...) | Lookahead - match on the characters following. e.g. /ab(?=c)/ match "ab" only when followed by "c" | (?!...) | Negative lookahead - match on characters that aren't following. e.g. /ab(?!c)/ match "ab" only when NOT followed by "c" | (?<=...) | Positive look-behind assertion. e.g. /(?<=foo)bar/ matches "bar" when preceded by "foo" | (?<!...) | Negative look-behind assertion. e.g. /(?<!foo)bar/ - matches "bar" when not preceded by "foo" | (?#...) | Comment e.g. (?# This comment is ignored entirely) |
Unicode character support\x0000-\xFFFF | Unicode hexadecimal character set | \x00-\xFF | ASCII hexadecimal character set | \cA-\cZ | Control characters |
Unicode is not fully supported on all platforms. JavaScript prior to ES6 for example allows ASCII hex but not full Unicode hex. | | Special Characters\n | New line | \r | Carriage return | \t | Tab | \v | Vertical tab | \f | Form feed |
Quantifiers* | Zero or more | + | One or more | ? | Zero or One (i.e. optional) | {n} | Exactly 'n' (any number) | {n,} | Minimum ('n' or more) | {n,m} | Range ('n' or more, but less or equal to 'm') |
Flags (expression modifiers)/m | Milti-line. (Makes ^ and $ match the start and end of a line respectively) | /s | Treat input as a single line. (Makes '.' match new lines as well) | /i | Case insensitive pattern matching. | /g | Global matching. (Don't stop after first match in a replacement function) | /x | Extended matching. (disregard white-space not explicitly escaped, and allow comments starting with #) |
Escape CharactersIn regular expressions, the following characters have special meaning and must be escaped: ^ $ [ { ( ) < > . * \ + | ?
Additionally the hyphen (-) and close square bracket (]) must be escaped when in an expression set ([...]).
e.g. /\(\d{3}\) \d{4}[\- ]\d{4}/ matches "(nnn) nnnn-nnnn" or "(nnn) nnnn nnnn" (where n is a numeric digit). |
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Greetings, and thanks for providing this.
Where can I find a comprehensive, accessible textual reference on this topic that includes numerous examples? Instead of pursuing blind trial and error, I would like to understand thoroughly what I am doing, and why.
Thanks.
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