Negative lookahead assertion: Matches “x” only if “x” is not followed by “y”. For example, /\d (?!\.)/ matches a number only if it is not followed by a decimal point. However, neither “Sprat” nor “Frost” is part of the match results. Jack(?=Sprat|Frost)/ matches “Jack” only if it is followed by “Sprat” or “Frost”. “Jack” only if it is followed by “Sprat”. Lookahead assertion: Matches “x” only if “x” is followed by “y”. Same as the matched word boundary, the matched non-word boundary is also not included in the match.įor example, /\Bon/ matches “on” in “at noon”, and /ye\B/ matches “ye” in “possibly yesterday”. 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. To match a backspace character ( ), see Character Classes. /\w\b\w/ will never match anything, because a word character can never be followed by both a non-word and a word character./oon\b/ matches the “oon” in “moon”, because “oon” is the end of the string, thus not followed by a word character./oo\b/ does not match the “oo” in “moon”, because “oo” is followed by “n” which is a word character.In other words, the length of a matched word boundary is zero. Note that a matched word boundary is not included in the match. 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. If the multiline flag is set to true, also matches immediately before a line break character.įor example, /t$/ does not match the “t” in “eater”, but does match it in “eat”. Note: This character has a different meaning when it appears at the start of a group. To match * literally, precede it with a backslash for example, /a\*/ matches “a*”. For example, “*” is a special character that means 0 or more occurrences of the preceding character should be matched for example, /a*/ means match 0 or more “a”s. For characters that are usually treated specially, indicates that the next character is not special and should be interpreted literally.By placing a backslash in front of “b”, that is by using /\b/, the character becomes special to mean match a word boundary. For characters that are usually treated literally, indicates that the next character is special and not to be interpreted literally.įor example, /b/ matches the character “b”.Indicates that the following character should be treated specially, or “escaped”. Matches a character based on its Unicode character properties (to match just, for example, emoji characters, or Japanese katakana characters, or Chinese/Japanese Han/Kanji characters, etc.). (Only when the u flag is set.) Matches the character with the Unicode value U hhhh or U hhhhh (hexadecimal digits). Matches a UTF-16 code-unit with the value hhhh (four hexadecimal digits). Matches the character with the code hh (two hexadecimal digits). Matches a control character using caret notation, where “X” is a letter from A–Z (corresponding to codepoints If you’re looking for the word-boundary character ( \b), see Assertions. įor example, /\S\w*/ matches “foo” in “foo bar”. Matches a single character other than white space. įor example, /\s\w*/ matches ” bar” in “foo bar”. Matches a single white space character, including space, tab, form feed, line feed, and other Unicode spaces. Matches any character that is not a word character from the basic Latin alphabet. Matches any alphanumeric character from the basic Latin alphabet, including the underscore. For example, /\D/ or // matches “B” in “B2 is the suite number”. Matches any character that is not a digit (Arabic numeral). įor example, /\d/ or // matches “2” in “B2 is the suite number”. So to match a pattern across multiple lines, the character class can be used - it will match any character including newlines.ĮS2018 added the s “dotAll” flag, which allows the dot to also match line terminators. ![]() ![]() Note that the m multiline flag doesn’t change the dot behavior. Inside a character class, the dot loses its special meaning and matches a literal dot.Matches any single character except line terminators: \n, \r, \u2028 or \u2029. For example, /.y/ matches “my” and “ay”, but not “yes”, in “yes make my day”.Table Of Contents Characters / constructs A simple Regex syntax cheat sheet that helps beginners get started with learning boring regular expressions.
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