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JavaScript RegExp Reference


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 Regular Expressions, read our JavaScript RegExp 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 between the brackets
[^0-9] Find any digit NOT between the brackets
(x|y) 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
constructor Returns the function that created the RegExp object's prototype
global Checks whether the "g" modifier is set
ignoreCase Checks whether the "i" modifier is set
lastIndex Specifies the index at which to start the next match
multiline Checks whether the "m" modifier is set
source Returns the text of the RegExp pattern

RegExp Object Methods

Method Description
compile() Deprecated in version 1.5. 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
toString() Returns the string value of the regular expression



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