JavaScript: Regular Expressions

Original source: http://www.johnrobertmorris.com/dev/Regex.asp By JohnRobertMorris
Archived by Darren's Outpost

Creating the Regular Expression Object

Type	Usage	Example	Note
Literal way	`/pattern/flags`	`var objRegex = /ab+c/i`	Do not use quotation marks to indicate strings.
Constructor method	`new RegExp("pattern"[, "flags"])`	`var objRegex = new RegExp("ab+c", "i")`	The normal escape rules apply (using the \ character).

Regular Expression Flags

Character	Description
`g`	global match
`i`	ignore case
`gi`	both global match and ignore case

Methods that use Regular Expressions

Method	Type	Description
`exec`	RegExp	Executes a search for a match in a string. It returns an array of information.
`test`	RegExp	Tests for a match in a string. It returns true or false.
`match`	String	Executes a search for a match in a string. It returns an array of information or null on a mismatch.
`search`	String	Tests for a match in a string. It returns the index of the match, or -1 if the search fails.
`replace`	String	Executes a search for a match in a string, and replaces the matched substring with a replacement substring.
`split`	String	Uses a regular expression or a fixed string to break a string into an array of substrings.

Pattern Syntax

Character	Meaning
`\`	Indicates next character should not be interpreted literally if it normally is, and should be interpreted literally if it normally isn't.
`^`	Matches beginning of input or line.
`$`	Matches end of input or line.
`*`	Matches 0 or more instances of preceding character.
`+`	Matches 1 or more instances of preceding character.
`?`	Matches 0 or 1 instances of preceding character.
`.`	Matches any single character other than the newline character.
`(x)`	Matches x and remembers the match.
`x\|y`	Matches either x or y.
	Matches exactly n instances of preceding character (where n is an integer).
`{n,}`	Matches at least n instances of preceding character (where n is an integer).
`{n,m}`	Matches it least n and at most m instances of preceding character (where n and m are integers).
`[xyz]`	Matches any one of enclosed characters (specify range using hyphen, such as [0-9].
`[^xyz]`	Matches any character not enclosed (specify range using hyphen, such as [^0-9].
`[\b]`	Matches a backspace.
`\b`	Matches a word boundary, such as a space.
`\B`	Matches a nonword boundary.
`\cX`	Matches a control character, X.
`\d`	Matches a digit character (same as [0-9]).
`\D`	Matches a nondigit character (same as [^0-9]).
`\f`	Matches a form feed.
`\n`	Matches a line feed.
`\r`	Matches a carriage return.
`\s`	Matches a single white space character, including space, tab, form feed, and line feed (same as [\f\n\r\t\v]).
`\S`	Matches a single non-white-space character (same as [^\f\n\r\t\v]).
`\t`	Matches a tab.
`\v`	Matches a vertical tab.
`\w`	Matches any alphanumeric character, including the underscore (same as [A-Za-z0-9_]).
`\W`	Matches any nonword character (same as [^A-Za-z0-9_]).
`\n`	A reference to the last substring matching the nth parenthetical (where n is a positive integer).
`\ooctal \xhex`	Matches an octal or hexadecimal escape value (for embedding ASCII codes).

Property Summary

Property	Description
`$1, ..., $9`	Parenthesized substring matches, if any.
`constructor`	Specifies the function that creates an object's prototype.
`global`	Whether or not to test the regular expression against all possible matches in a string, or only against the first.
`ignoreCase`	Whether or not to ignore case while attempting a match in a string.
`$_ input`	The string against which a regular expression is matched.
`lastIndex`	The index at which to start the next match.
`$& lastMatch`	The last matched characters.
`$+ lastParen`	The last parenthesized substring match, if any.
$` leftContext	The substring preceding the most recent match.
`$* multiline`	Whether or not to search in strings across multiple lines.
`prototype`	Allows the addition of properties to all objects.
`$' rightContext`	The substring following the most recent match.
`source`	The text of the pattern.

Method Summary

Method	Description
`compile`	Compiles a regular expression object.
`exec`	Executes a search for a match in its string parameter.
`test`	Tests for a match in its string parameter.
`toSource`	Returns an object literal representing the specified object; you can use this value to create a new object. Overrides the `Object.toSource` method.
`toString`	Returns a string representing the specified object. Overrides the `Object.toString` method.
`valueOf`	Returns the primitive value of the specified object. Overrides the `Object.valueOf` method.