RegExp

For an introduction to regular expressions, read the Regular Expressions chapter in the JavaScript Guide.

Description

Strings are useful for holding data that can be represented in text form. Some of the most-used operations on strings are to check their length, to build and concatenate them using the + and += string operators, checking for the existence or location of substrings with the indexOf() method, or extracting substrings with the substring() method.

Regular expressions are patterns used to match character combinations in strings. In JavaScript, regular expressions are also objects. These patterns are used with the exec() and test() methods of RegExp, and with the match(), matchAll(), replace(), replaceAll(), search(), and split() methods of String. This chapter describes JavaScript regular expressions.

Creating a regular expression

Using a regular expression literal, which consists of a pattern enclosed between slashes, as follows:

let re = /ab+c/;

Regular expression literals provide compilation of the regular expression when the script is loaded. If the regular expression remains constant, using this can improve performance.

Or calling the constructor function of the RegExp object, as follows:

let re = new RegExp('ab+c');

Using special characters

Special characters in regular expressions.
Characters / constructs	Corresponding article
\, ., \cX, \d, \D, \f, \n, \r, \s, \S, \t, \v, \w, \W, \0, \xhh, \uhhhh, \uhhhhh, [\b]	Character classes
^, $, x(?=y), x(?!y), (?<=y)x, (?<!y)x, \b, \B	Assertions
(x), (?:x), (?<Name>x), x|y, [xyz], [^xyz], \Number	Groups and ranges
*, +, ?, x{n}, x{n,}, x{n,m}	Quantifiers
\p{UnicodeProperty}, \P{UnicodeProperty}	Unicode property escapes