This page provides an overall cheat sheet of all the capabilities of RegExp syntax by aggregating the content of the articles in the RegExp guide. If you need more information on a specific topic, please follow the link on the corresponding heading to access the full article or head to the guide.
Character classes distinguish kinds of characters such as, for example, distinguishing between letters and digits. Character class: Matches any one of the enclosed characters. You can specify a range of characters by using a hyphen, but if the hyphen appears as the first or last character enclosed in the square brackets, it is taken as a literal hyphen to be included in the character class as a normal character. For example, For example, For example, Negated character class: Matches anything that is not enclosed in the square brackets. You can specify a range of characters by using a hyphen, but if the hyphen appears as the first character after the Note: The ^ character may also indicate the beginning of input. Wildcard: Matches any single character except line terminators: Digit character class escape: Matches any digit (Arabic numeral). Equivalent to Non-digit character class escape: Matches any character that is not a digit (Arabic numeral). Equivalent to Word character class escape: Matches any alphanumeric character from the basic Latin alphabet, including the underscore. Equivalent to Non-word character class escape: Matches any character that is not a word character from the basic Latin alphabet. Equivalent to White space character class escape: Matches a single white space character, including space, tab, form feed, line feed, and other Unicode spaces. Equivalent to Non-white space character class escape: Matches a single character other than white space. Equivalent to Matches a control character using caret notation, where "X" is a letter from A–Z or a–z (corresponding to code points Unicode character class escape: Matches a character based on its Unicode character properties: for example, emoji characters, or Japanese katakana characters, or Chinese/Japanese Han/Kanji characters, etc.). Indicates that the following character should be treated specially, or "escaped". It behaves one of two ways. Note: To match this character literally, escape it with itself. In other words to search for Disjunction: Matches either "x" or "y". Each component, separated by a pipe ( Note: A disjunction is another way to specify "a set of choices", but it's not a character class. Disjunctions are not atoms — you need to use a group to make it part of a bigger pattern. Characters Meaning [xyz]
[a-c][abcd] is the same as [a-d]. They match the "b" in "brisket", and the "c" in "chop".[abcd-] and [-abcd] match the "b" in "brisket", the "c" in "chop", and the "-" (hyphen) in "non-profit".[\w-] is the same as [A-Za-z0-9_-]. They both match the "b" in "brisket", the "c" in "chop", and the "n" in "non-profit".[^xyz]
[^a-c]^ or the last character enclosed in the square brackets, it is taken as a literal hyphen to be included in the character class as a normal character. For example, [^abc] is the same as [^a-c]. They initially match "o" in "bacon" and "h" in "chop"..\n, \r, \u2028 or \u2029. For example, /.y/ matches "my" and "ay", but not "yes", in "yes make my day", as there is no character before "y" in "yes". If the dotAll (s) flag is enabled, also matches line terminators. Inside a character class, the dot loses its special meaning and matches a literal dot.\d[0-9]. For example, /\d/ or /[0-9]/ matches "2" in "B2 is the suite number".\D[^0-9]. For example, /\D/ or /[^0-9]/ matches "B" in "B2 is the suite number".\w[A-Za-z0-9_]. For example, /\w/ matches "a" in "apple", "5" in "$5.28", "3" in "3D" and "m" in "Émanuel".\W[^A-Za-z0-9_]. For example, /\W/ or /[^A-Za-z0-9_]/ matches "%" in "50%" and "É" in "Émanuel".\s[\f\n\r\t\v\u0020\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]. For example, /\s\w*/ matches " bar" in "foo bar".\S[^\f\n\r\t\v\u0020\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]. For example, /\S\w*/ matches "foo" in "foo bar".\tMatches a horizontal tab. \rMatches a carriage return. \nMatches a linefeed. \vMatches a vertical tab. \fMatches a form-feed. [\b]Matches a backspace. If you're looking for the word-boundary assertion ( \b), see Assertions.\0Matches a NUL character. Do not follow this with another digit. \cXU+0001–U+001A). For example, /\cM\cJ/ matches "\r\n".\xhhHex escape: Matches the character with the code hh (two hexadecimal digits).\uHHHHUnicode escape: Matches a UTF-16 code-unit with the value HHHH (four hexadecimal digits).\u{H…H}Unicode code point escape: (Only when the u flag is set.) Matches the character with the Unicode value U+H…H (1 to 6 hexadecimal digits).\p{UnicodeProperty}, \P{UnicodeProperty}\/b/ matches the character "b". By placing a backslash in front of "b", that is by using /\b/, the character becomes special to mean match a word boundary./a*/ means match 0 or more "a"s. To match * literally, precede it with a backslash; for example, /a\*/ matches "a*".\ use /\\/.x|y|), is called an alternative. For example, /green|red/ matches "green" in "green apple" and "red" in "red apple".[abc] is functionally equivalent to (?:a|b|c).
Assertions include boundaries, which indicate the beginnings and endings of lines and words, and other patterns indicating in some way that a match is possible (including look-ahead, look-behind, and conditional expressions).
| Characters | Meaning |
|---|---|
^ | Input boundary beginning assertion: Matches the beginning of input. If the Note: This character has a different meaning when it appears at the start of a character class. |
$ | Input boundary end assertion: Matches the end of input. If the |
\b | Word boundary assertion: Matches a word boundary. This is the position where a word character is not followed or preceded by another word-character, such as between a letter and a space. Note that a matched word boundary is not included in the match. In other words, the length of a matched word boundary is zero. Examples:
To match a backspace character ( |
\B | Non-word-boundary assertion: Matches a non-word boundary. This is a position where the previous and next character are of the same type: Either both must be words, or both must be non-words, for example between two letters or between two spaces. The beginning and end of a string are considered non-words. Same as the matched word boundary, the matched non-word boundary is also not included in the match. For example, |
Note: The ? character may also be used as a quantifier.
| Characters | Meaning |
|---|---|
x(?=y) | Lookahead assertion: Matches "x" only if "x" is followed by "y". For example, |
x(?!y) | Negative lookahead assertion: Matches "x" only if "x" is not followed by "y". For example, |
(?<=y)x | Lookbehind assertion: Matches "x" only if "x" is preceded by "y". For example, |
(?<!y)x | Negative lookbehind assertion: Matches "x" only if "x" is not preceded by "y". For example, |
Groups and backreferences indicate groups of expression characters. Capturing group: Matches A regular expression may have multiple capturing groups. In results, matches to capturing groups typically in an array whose members are in the same order as the left parentheses in the capturing group. This is usually just the order of the capturing groups themselves. This becomes important when capturing groups are nested. Matches are accessed using the index of the result's elements ( Capturing groups have a performance penalty. If you don't need the matched substring to be recalled, prefer non-capturing parentheses (see below). Named capturing group: Matches "x" and stores it on the groups property of the returned matches under the name specified by For example, to extract the United States area code from a phone number, we could use Non-capturing group: Matches "x" but does not remember the match. The matched substring cannot be recalled from the resulting array's elements ( Modifier: Enables or disables the specified flags only to the enclosed pattern. Only the Backreference: Where "n" is a positive integer. Matches the same substring matched by the nth capturing group in the regular expression (counting left parentheses). For example, Named backreference: A back reference to the last substring matching the Named capture group specified by For example, Note: Characters Meaning (x)x and remembers the match. For example, /(foo)/ matches and remembers "foo" in "foo bar".[1], …, [n]) or from the predefined RegExp object's properties ($1, …, $9).String.prototype.match() won't return groups if the /.../g flag is set. However, you can still use String.prototype.matchAll() to get all matches.(?<Name>x)<Name>. The angle brackets (< and >) are required for group name./\((?<area>\d\d\d)\)/. The resulting number would appear under matches.groups.area.(?:x)[1], …, [n]) or from the predefined RegExp object's properties ($1, …, $9).(?flags:x), (?flags-flags:x)i, m, and s flags can be used in a modifier.\n/apple(,)\sorange\1/ matches "apple, orange," in "apple, orange, cherry, peach".\k<Name><Name>./(?<title>\w+), yes \k<title>/ matches "Sir, yes Sir" in "Do you copy? Sir, yes Sir!".\k is used literally here to indicate the beginning of a back reference to a Named capture group.
Quantifiers indicate numbers of characters or expressions to match.
Note: In the following, item refers not only to singular characters, but also includes character classes and groups and backreferences.
| Characters | Meaning |
|---|---|
x* | Matches the preceding item "x" 0 or more times. For example, |
x+ | Matches the preceding item "x" 1 or more times. Equivalent to |
x? | Matches the preceding item "x" 0 or 1 times. For example, If used immediately after any of the quantifiers |
x{n} | Where "n" is a non-negative integer, matches exactly "n" occurrences of the preceding item "x". For example, |
x{n,} | Where "n" is a non-negative integer, matches at least "n" occurrences of the preceding item "x". For example, |
x{n,m} | Where "n" and "m" are non-negative integers and |
| By default quantifiers like
Note: Adding |