JavaScript RegExp Patterns
New to RegExp?
let regexp = /pattern/flags;
// or
let regext = new RegExp(pattern, flags)
// or
let regext = new RegExp(pattern, flags)
RexExp Flags / Modifiers
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) |
RexExp Character Classes
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 |
| [^0-9] | Matches all characters NOT in the range from 0 to 9 |
RexExp Metacharacters
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円
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)
\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
RexExp Assertions
Assertions include boundaries, which indicate the beginnings and endings of lines and words:
| 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 Groups
Regular Expression Groups (aka capturing groups) allows parts of a matched string to be extracted and reused. They are created by enclosing a pattern within parentheses ():
| Char | Description |
|---|---|
| (x) | Matches x and remembers the match |
| (?<n>x) | Matches x and labels it n |
| (?flag:x) | Enables flag(s) for x |
| (?flag-flag:x) | Disables flag(s) for x |
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 |
Browser Support
/regexp/ is an ECMAScript1 (JavaScript 1997) feature.
It is supported in all browsers:
| Chrome | Edge | Firefox | Safari | Opera |