JavaScript Regex Cheatsheet
Regular Expression quick reference guide
Normal Characters
| Expression | Description |
|---|---|
| . | Any character excluding a newline or carriage return |
| [A-Za-z] | Alphabet (both uppercase and lowercase) |
| [a-z] | Lowercase alphabet |
| [A-Z] | Uppercase alphabet |
| \d or [0-9] | Digit |
| \D or [^0-9] | Non-digit |
| _ | Underscore |
| \w or [A-Za-z0-9_] | Alphabet, digit, or underscore |
| \W or [^A-Za-z0-9_] | Inverse of \w (not alphabet, digit, or underscore) |
| \s | Space, tab, newline, or carriage return |
| \S | Inverse of \s (not space, tab, newline, or carriage return) |
Whitespace Characters
| Expression | Description |
|---|---|
| Space | |
| \t | Tab |
| \n | Newline |
| \r | Carriage return |
| \s | Space, tab, newline, or carriage return |
Boundaries
| Expression | Description |
|---|---|
| ^ | Start of string |
| $ | End of string |
| \b | Word boundary |
Notes:
- How word boundary matching works:
- At the beginning of the string if the first character is \w.
- Between two adjacent characters within the string, if the first character is \w and the second character is \W.
- At the end of the string if the last character is \w.
Matching
| Expression | Description |
|---|---|
| foo|bar | Match either foo or bar |
| foo(?=bar) | Match foo if it's before bar |
| foo(?!bar) | Match foo if it's not before bar |
| (?<=bar)foo | Match foo if it's after bar |
| (?<!bar)foo | Match foo if it's not after bar |
Grouping and Capturing
| Expression | Description |
|---|---|
| (foo) | Capturing group; match and capture foo |
| (?:foo) | Non-capturing group; match foo but without capturing foo |
| (foo)bar\1 | \1 is a backreference to the 1st capturing group; match foobarfoo |
Notes:
- Capturing groups are only relevant in the following methods:
- string.match(regex)
- string.matchAll(regex)
- string.replace(regex, callback)
- \n is a backreference to the nth capturing group. Capturing groups are numbered starting from 1.
Character Set
| Expression | Description |
|---|---|
| [xyz] | Either x, y, or z |
| [^xyz] | Neither x, y, nor z |
| [1-3] | Either 1, 2, or 3 |
| [^1-3] | Neither 1, 2, nor 3 |
Notes:
- Think of a character set as an OR operation on the single characters that are enclosed between the square brackets [...].
- Use ^ after the opening [ to 'negate' the character set.
- Within a character set, . means a literal period.
Quantifiers
| Expression | Description |
|---|---|
| {2} | Exactly 2 |
| {2,} | At least 2 |
| {2,7} | At least 2 but no more than 7 |
| * | 0 or more |
| + | 1 or more |
| ? | Exactly 0 or 1 |
Notes:
- The quantifier goes after the expression to be quantified.
Characters That Require Escaping
| Expression | Description |
|---|
Outside a Character Set
| Expression | Description |
|---|---|
| \. | Period |
| \^ | Caret |
| \$ | Dollar sign |
| \| | Pipe |
| \\ | Back slash |
| \/ | Forward slash |
| \( | Opening bracket |
| \) | Closing bracket |
| \[ | Opening square bracket |
| \] | Closing square bracket |
| \{ | Opening curly bracket |
| \} | Closing curly bracket |
Inside a Character Set
| Expression | Description |
|---|---|
| \\ | Back slash |
| \] | Closing square bracket |
Notes:
- ^ must be escaped only if it occurs immediately after the opening [ of the character set.
- - must be escaped only if it occurs between two alphabets or two digits.