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JavaScript RegExp Object

RegExp Object

A regular expression is an object that describes a pattern of characters.

Regular expressions are used to perform pattern-matching and "search-and-replace" functions on text.

Syntax

var patt=new RegExp(pattern,modifiers);

or more simply:

var patt=/pattern/modifiers;
  • pattern specifies the pattern of an expression
  • modifiers specify if a search should be global, case-sensitive, etc.

For a tutorial about the RegExp object, read our JavaScript RegExp Object tutorial.

Modifiers

Modifiers are used to perform case-insensitive and global searches:

Modifier Description
i Perform case-insensitive matching
g Perform a global match (find all matches rather than stopping after the first match)
m Perform multiline matching

Brackets

Brackets are used to find a range of characters:

Expression Description
[abc] Find any character between the brackets
[^abc] Find any character not between the brackets
[0-9] Find any digit from 0 to 9
[A-Z] Find any character from uppercase A to uppercase Z
[a-z] Find any character from lowercase a to lowercase z
[A-z] Find any character from uppercase A to lowercase z
[adgk] Find any character in the given set
[^adgk] Find any character outside the given set
(red|blue|green) Find any of the alternatives specified

Metacharacters

Metacharacters are characters with a special meaning:

Metacharacter Description
. Find a single character, except newline or line terminator
\w Find a word character
\W Find a non-word character
\d Find a digit
\D Find a non-digit character
\s Find a whitespace character
\S Find a non-whitespace character
\b Find a match at the beginning/end of a word
\B Find a match not at the beginning/end of a word
\0 Find a NUL character
\n Find a new line character
\f Find a form feed character
\r Find a carriage return character
\t Find a tab character
\v Find a vertical tab character
\xxx Find the character specified by an octal number xxx
\xdd Find the character specified by a hexadecimal number dd
\uxxxx Find the Unicode character specified by a hexadecimal number xxxx

Quantifiers

Quantifier Description
n+ Matches any string that contains at least one n
n* Matches any string that contains zero or more occurrences of n
n? Matches any string that contains zero or one occurrences of n
n{X} Matches any string that contains a sequence of X n's
n{X,Y} Matches any string that contains a sequence of X to Y n's
n{X,} Matches any string that contains a sequence of at least X n's
n$ Matches any string with n at the end of it
^n Matches any string with n at the beginning of it
?=n Matches any string that is followed by a specific string n
?!n Matches any string that is not followed by a specific string n

RegExp Object Properties

Property Description
global Specifies if the "g" modifier is set
ignoreCase Specifies if the "i" modifier is set
lastIndex The index at which to start the next match
multiline Specifies if the "m" modifier is set
source The text of the RegExp pattern

RegExp Object Methods

Method Description
compile() Compiles a regular expression
exec() Tests for a match in a string. Returns the first match
test() Tests for a match in a string. Returns true or false

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