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Extended regular expressions

XRegExp 3.1.1

XRegExp provides augmented (and extensible) JavaScript regular expressions. You get new modern syntax and flags beyond what browsers support natively. XRegExp is also a regex utility belt with tools to make your client-side grepping and parsing easier, while freeing you from worrying about pesky aspects of JavaScript regexes like cross-browser inconsistencies or manually manipulating lastIndex.

XRegExp supports all native ES6 regular expression syntax. It supports Internet Explorer 5.5+, Firefox 1.5+, Chrome, Safari 3+, and Opera 11+. You can also use it with Node.js or as a RequireJS module.


XRegExp regexes compile to native RegExp objects, and therefore perform just as fast as native regular expressions. There is a tiny extra cost when compiling a pattern for the first time.

Usage examples

// Using named capture and flag x (free-spacing and line comments) 
var date = XRegExp('(?<year>  [0-9]{4} ) -?  # year  \n\
                    (?<month> [0-9]{2} ) -?  # month \n\
                    (?<day>   [0-9]{2} )     # day   ', 'x');
// XRegExp.exec gives you named backreferences on the match result 
var match = XRegExp.exec('2015-02-22', date);
match.year; // -> '2015' 
// It also includes optional pos and sticky arguments 
var pos = 3;
var result = [];
while (match = XRegExp.exec('<1><2><3><4>5<6>', /<(\d+)>/, pos, 'sticky')) {
    pos = match.index + match[0].length;
// result -> ['2', '3', '4'] 
// XRegExp.replace allows named backreferences in replacements 
XRegExp.replace('2015-02-22', date, '${month}/${day}/${year}');
// -> '02/22/2015' 
XRegExp.replace('2015-02-22', date, function(match) {
    return match.month + '/' + + '/' + match.year;
// -> '02/22/2015' 
// In fact, XRegExps compile to RegExps and work perfectly with native methods 
// -> true 
// The only caveat is that named captures must be referenced using numbered 
// backreferences if used with native methods 
'2015-02-22'.replace(date, '$2/$3/$1');
// -> '02/22/2015' 
// Extract every other digit from a string using XRegExp.forEach 
var evens = [];
XRegExp.forEach('1a2345', /\d/, function(match, i) {
    if (% 2) evens.push(+match[0]);
// evens -> [2, 4] 
// Get numbers within <b> tags using XRegExp.matchChain 
XRegExp.matchChain('1 <b>2</b> 3 <b>4 a 56</b>', [
// -> ['2', '4', '56'] 
// You can also pass forward and return specific backreferences 
var html = '<a href="">XRegExp</a>' +
           '<a href="">Google</a>';
XRegExp.matchChain(html, [
    {regex: /<a href="([^"]+)">/i, backref: 1},
    {regex: XRegExp('(?i)^https?://(?<domain>[^/?#]+)'), backref: 'domain'}
// -> ['', ''] 
// Merge strings and regexes into a single pattern with updated backreferences 
XRegExp.union(['a+b*c', /(dog)\1/, /(cat)\1/], 'i');
// -> /a\+b\*c|(dog)\1|(cat)\2/i 

These examples give the flavor of what's possible, but XRegExp has more syntax, flags, methods, options, and browser fixes that aren't shown here. You can even augment XRegExp's regular expression syntax with addons (see below) or write your own. See for details.


You can either load addons individually, or bundle all addons with XRegExp by loading xregexp-all.js.


If not using xregexp-all.js, first include the Unicode Base script and then one or more of the addons for Unicode blocks, categories, properties, or scripts.

Then you can do this:

// Test the Unicode category L (Letter) 
var unicodeWord = XRegExp('^\\pL+$');
unicodeWord.test('Русский'); // -> true 
unicodeWord.test('日本語'); // -> true 
unicodeWord.test('العربية'); // -> true 
// Test some Unicode scripts 
XRegExp('^\\p{Hiragana}+$').test('ひらがな'); // -> true 
XRegExp('^[\\p{Latin}\\p{Common}]+$').test('Über Café.'); // -> true 

By default, \p{…} and \P{…} support the Basic Multilingual Plane (i.e. code points up to U+FFFF). You can opt-in to full 21-bit Unicode support (with code points up to U+10FFFF) on a per-regex basis by using flag A. In XRegExp, this is called astral mode. You can automatically add flag A for all new regexes by running XRegExp.install('astral'). When in astral mode, \p{…} and \P{…} always match a full code point rather than a code unit, using surrogate pairs for code points above U+FFFF.

// Using flag A to match astral code points 
XRegExp('^\\pS$').test('💩'); // -> false 
XRegExp('^\\pS$', 'A').test('💩'); // -> true 
XRegExp('(?A)^\\pS$').test('💩'); // -> true 
// Using surrogate pair U+D83D U+DCA9 to represent U+1F4A9 (pile of poo) 
XRegExp('(?A)^\\pS$').test('\uD83D\uDCA9'); // -> true 
// Implicit flag A 
XRegExp('^\\pS$').test('💩'); // -> true 

Opting in to astral mode disables the use of \p{…} and \P{…} within character classes. In astral mode, use e.g. (\pL|[0-9_])+ instead of [\pL0-9_]+.

XRegExp uses Unicode 8.0.0.

Build regular expressions using named subpatterns, for readability and pattern reuse:

var time ='(?x)^ {{hours}} ({{minutes}}) $', {
    hours:'{{h12}} : | {{h24}}', {
        h12: /1[0-2]|0?[1-9]/,
        h24: /2[0-3]|[01][0-9]/
    minutes: /^[0-5][0-9]$/
time.test('10:59'); // -> true 
XRegExp.exec('10:59', time).minutes; // -> '59' 

Named subpatterns can be provided as strings or regex objects. A leading ^ and trailing unescaped $ are stripped from subpatterns if both are present, which allows embedding independently-useful anchored patterns. {{…}} tokens can be quantified as a single unit. Any backreferences in the outer pattern or provided subpatterns are automatically renumbered to work correctly within the larger combined pattern. The syntax ({{name}}) works as shorthand for named capture via (?<name>{{name}}). Named subpatterns cannot be embedded within character classes.

See also: Creating Grammatical Regexes Using


Match recursive constructs using XRegExp pattern strings as left and right delimiters:

var str = '(t((e))s)t()(ing)';
XRegExp.matchRecursive(str, '\\(', '\\)', 'g');
// -> ['t((e))s', '', 'ing'] 
// Extended information mode with valueNames 
str = 'Here is <div> <div>an</div></div> example';
XRegExp.matchRecursive(str, '<div\\s*>', '</div>', 'gi', {
    valueNames: ['between', 'left', 'match', 'right']
/* -> [
{name: 'between', value: 'Here is ',       start: 0,  end: 8},
{name: 'left',    value: '<div>',          start: 8,  end: 13},
{name: 'match',   value: ' <div>an</div>', start: 13, end: 27},
{name: 'right',   value: '</div>',         start: 27, end: 33},
{name: 'between', value: ' example',       start: 33, end: 41}
// Omitting unneeded parts with null valueNames, and using escapeChar 
str = '...{1}.\\{{function(x,y){return {y:x}}}';
XRegExp.matchRecursive(str, '{', '}', 'g', {
    valueNames: ['literal', null, 'value', null],
    escapeChar: '\\'
/* -> [
{name: 'literal', value: '...',  start: 0, end: 3},
{name: 'value',   value: '1',    start: 4, end: 5},
{name: 'literal', value: '.\\{', start: 6, end: 9},
{name: 'value',   value: 'function(x,y){return {y:x}}', start: 10, end: 37}
// Sticky mode via flag y 
str = '<1><<<2>>><3>4<5>';
XRegExp.matchRecursive(str, '<', '>', 'gy');
// -> ['1', '<<2>>', '3'] 

XRegExp.matchRecursive throws an error if it scans past an unbalanced delimiter in the target string.

Installation and usage

In browsers (bundle XRegExp with all of its addons):

<script src="xregexp-all.js"></script>

Using npm:

npm install xregexp

In Node.js:

var XRegExp = require('xregexp');

In an AMD loader like RequireJS:

require({paths: {xregexp: 'xregexp-all'}}, ['xregexp'], function(XRegExp) {


XRegExp copyright 2007-2016 by Steven Levithan.

Unicode range generators by Mathias Bynens, and adapted from his unicode-data project. Uses Jasmine for unit tests, and Benchmark.js for performance tests. inspired by RegExp.create by Lea Verou. XRegExp.union inspired by Ruby. XRegExp's syntax extensions and flags come from Perl, .NET, etc.

All code, including addons, tools, and tests, is released under the terms of the MIT License.

Fork me to show support, fix, and extend.