Revised July 2025
Flags can be added to a regexp pattern to Modify its behavior:
| Flag | Description |
|---|---|
| /d | Performs substring matches (new 2022) |
| /g | Performs a global match (find all) |
| /i | Performs case-insensitive matching |
| /m | Performs multiline matching |
| /s | Allows . (dot) to match line terminators (new 2018) |
| /u | Enables Unicode support (new 2015) |
| /v | An upgrade to the /u flag for better Unicode support (new 2025) |
| /y | Performs a "sticky" search (new 2015) |
Revised July 2025
A character class is one or more characters enclosed in square brackets [ ] :
| Class | Description |
|---|---|
| [a] | Matches the character between the brackets |
| [^a] | Matches all characters NOT between the brackets |
| [abc] | Matches all characters between the brackets |
| [^abc] | Matches all characters NOT between the brackets |
| [a-z] | Matches all characters in the range from a to z |
| [^a-z] | Matches all characters NOT in the range from a to z |
| [0-9] | Matches all characters in the range from 0 to 9 |
Revised July 2025
Metacharacters are characters with a special meaning:
| a | b | Matches a or b |
|---|---|---|
| . | Matches any (wildcard) character except line terminators | |
| \w | Matches word characters (alphanumeric and _) | |
| \W | Matches non-word characters | |
| \d | Matches digits (0-9) | |
| \D | Matches non-digit characters | |
| \s | Matches whitespace characters (space, tab, newline) | |
| \S | Matches non-whitespace character | |
| [\b] | Matches backspace characters | |
| \0 | Matches NULL characters | |
| \n | Matches new line characters | |
| \f | Matches form feed characters | |
| \r | Matches carriage returns characters | |
| \t | Matches tab characters | |
| \v | Matches vertical tab characters | |
| \p{} | Matches characters with given Unicode Property (new 2018) | |
| \P{} | Matches character NOT with the given Unicode Property (new 2018) | |
| \ddd | Matches a character by the octal number ddd | |
| \xhh | Matches a character by the hexadecimal number hh | |
| \uhhhh | Matches a Unicode character by the hex number hhhh |
Revised July 2025
Assertions consist of Boundaries and Lookarounds .
Boundaries matches at the beginning or the end of lines and words, Lookarounds mathes previos or subsequent patterns.
| Char | Description |
|---|---|
| ^ | Matches from beginning of a string, or the beginning of a line if the m (multiline) flag is set |
| $ | Matches from the end of a string, or the end of a line if the m (multiline) flag is set |
| \b | Matches from the beginning or end of a word |
| \B | Matches NOT from the beginning or end of a word |
| (?=...) | Matches the subsequent string |
| (?!...) | Matches NOT the subsequent string |
| (?<=...) | Matches the previous string (new 2018) |
| (?<!...) | Matches NOT the previous string (new 2018) |
RexExp Quantifiers
Quantifiers indicate the numbers of characters or expressions to match:
| Code | Description |
|---|---|
| x+ | Matches at least one x |
| x* | Matches zero or more occurrences of x |
| x? | Matches zero or one occurrences of x |
| x{n} | Matches n occurences of x |
| x{n,m} | Matches from n to m occurences of x |
| x{n,} | Matches n or more occurences of x |