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Links

• See also:
  • XRegExp: A JavaScript regex library that supports all native ES5 regular expression syntax, verbose mode, free scoping, etc.
  • regexpu: Transpiles ES6 Unicode regular expressions to ES5.
• All MDN Articles
• Regular Expressions
  • When you want to know whether a pattern is found in a string, use the test or search method; for more information (but slower execution) use the exec or match methods.
• RegExp
• regular-expressions.info
• Some limitations to be aware of:
  • No named capturing groups :(
  • No lookbehind (but you can lookahead.)
  • Unicode support is limited to matching specific codepoints via \uFFFF.

Flags

Flag	Property	Description
g	global	Changes methods test() and exec() to start the search at lastIndex instead of the beginning of the string. Changes string.match to returns all matches and string.split to split at all matches.
i	ignoreCase	ignore case.
m	multiline	Changes ^ and $ to match at the beginning and end of a line. However, . still won't match across newlines. Use [\s\S] as an alternative.
y	(ES6) sticky	Changes exec and test to match at lastIndex instead of conducting a search. Finally!

Properties

Property	Type	RW	Description
lastIndex	int	RW	specifies the index at which to start the next search.
source	string	R	the source text of the regexp object (without flags).
global	bool	R	true if the RegExp was constructed with the global ("g") flag.
ignoreCase	bool	R	true if the RegExp was constructed with the ignoreCase ("i") flag.
multiline	bool	R	true if the RegExp was constructed with the multiline ("m") flag.
sticky	bool	R	(ES6) true if the RegExp was constructed with the sticky ("y") flag.

Methods

Method	Description
regex.exec(str)	search for a match in a string. Returns an array of information.
regex.test(str)	tests for a match in a string. Returns true or false.
string.match(regex)	search for a match in a string. Returns an array of information or null on a mismatch.
string.search([regex])	tests for a match in a string. Returns the index of the match, or -1 if the search fails.
string.replace(regex/substr, newSubStr/function, [flags])	search for a match in a string, and replaces the matched substring with a replacement substring. See here for using a function
string.split([separator[, limit]])	uses a regular expression or a fixed string to break a string into an array of substrings.

HowTo

Make . match everything including newlines

There's no flag for this unfortunately. However you can use the character set [\s\S] instead to replace .. So, for example, /[\s\S]*/.test("abc\ndef\n123") == true.