JavaScript RegExp Reference

Last Updated : 05 Dec, 2024

RegExp stands for Regular Expression. A regular expression is a sequence of characters that forms a search pattern. The search pattern can be used for text search and text to replace operations. A regular expression can be a single character or a more complicated pattern.

Syntax:

new RegExp("(Regular Expressioncharactersnonword)")

Example: This example searches the words whose starting character is “A” and ending character is “C” with only one character in between them.

JavaScript

let str = "ABC, A3C, A C, AXXCC!"; let regex = /A.C/g; console.log(str.match(regex));

Output

[ 'ABC', 'A3C', 'A C' ]

The complete list of JavaScript RegExp is listed below:

JavaScript RegExp Constructor:

In JavaScript, a constructor gets called when an object is created using the new keyword.

RegExp(): It creates a new RegExp object.

JavaScript

const str = "geeksforgeeks" const reg = new RegExp(/[g]/, 'g'); console.log(str.match(reg));

Output

[ 'g', 'g' ]

JavaScript RegExp Properties: A JavaScript property is a member of an object that associates a key with a value.

Instance Property: An instance property is a property that has a new copy for every new instance of the class.

Instance Properties	Description
constructor	Return the RegExp constructor function for the object.
dotAll	It checks if the ‘s’ flag is used or not in the Regular Expression
flags	This property returns the flag being used in the current RegExp object
global	It specifies whether the ‘g’ flag is used or not
hasIndices	It specifies whether the ‘d’ flag is used or not
ignoreCase	It specifies whether the ‘i’ flag is used or not
multiline	It specifies whether ‘m’ flag is set or not
source	It returns the text of the RegExp object
sticky	It specifies whether ‘y’ flag is used or not
unicode	It specifies whether ‘u’ flag is used or not
lastIndex	It specifies at which index to start the next match

JavaScript RegExp Methods: JavaScript methods are the actions that can be performed on objects.

Instance Method:

If the method is called on an instance of a RegExp then it is called an instance method.

Instance Methods	Description
exec	It is used to test if the strings match
test	It also checks if the string matches but the return type is different
toString	It returns the string value of the Regular Expression

The Different Metacharacters and Flags of RegExp is given below:

RegExp	Description
Metacharacter	Search single characters, except line terminator or newline.
m	Perform multiline matching.
\r	The RegExp \r Metacharacter carriage return characters.
[abc]	Search for any character which is between the brackets.
(x\|y)	Search any of the specified characters (separated by \|).
\xxx	Find the character specified by an octal number xxx.
\W	Find the non word character i.e. characters which are not from a to z, A to Z, 0 to 9.
[^abc]	Search for any character which is not between the brackets.
g	Find all the occurrences of the pattern instead of stopping after the first match i.e it performs a global match.
[0-9]	Search any digit which is between the brackets.
\s	Find the whitespace characters.
\b	Find a match at the beginning or end of a word
i	Perform case-insensitive matching in the string.
\n	The RegExp \n Metacharacter in JavaScript is used to find the newline character.
[^0-9]	Search for any digit which is not between the brackets.
\B	Find a match that is not present at the beginning or end of a word.
\f	Find the form feed character (form feed is a page-breaking ASCII control character).
\w	Find the word character i.e. characters from a to z, A to Z, 0 to 9. It is the same as [a-zA-Z_0-9].
\d	Search digit characters. It is the same as [0-9].
\t	If it is found it returns the position else it returns -1.
\D	Search non-digit characters i.e all the characters except digits. It is the same as [^0-9].
\0	Find the NULL character. If it is found it returns the position else it returns -1.
\v	Find the vertical tab character. If it is found it returns the position else it returns -1.
*	Find the match of any string that contains zero or more occurrences of m.
{X,}	Find the match of any string that contains a sequence of m, at least X times, where X is a number.
?!	Find the match of any string which is not followed by a specific string m.
{X}	Find the match of any string that contains a sequence of m, X times where X is a number.
^	Find the match of any string which contains m at the beginning of it.
?	Find the match of any string that contains zero or one occurrence of m.
$	Find the match of any string which contains m at the end of it.
+	Find the match of any string that contains at least one m.
\uxxxx	Find the Unicode character specified by a hexadecimal number XXXX.
{X,Y}	Find the match of any string that contains a sequence of m, X to Y times where X, Y must be numbered.

JavaScript RegExp ?! Quantifier

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