XRegExp

XRegExp provides augmented, extensible JavaScript regular expressions. You get new syntax, flags, and methods beyond what browsers support natively. XRegExp is also a regular expression utility belt with tools to make your client-side grepping simpler and more powerful, while freeing you from worrying about pesky cross-browser inconsistencies and the dubious lastIndex property.

Usage examples

Note that these examples take advantage of new features in XRegExp v2.0.0-beta (details).

// 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('2012-02-22', date);
match.day; // -> '22'

// It also includes optional pos and sticky arguments
var pos = 2, result = [];
while (match = XRegExp.exec('<1><2><3><4>5<6>', /<(\d+)>/, pos, 'sticky')) {
    result.push(match[1]);
    pos = match.index + match[0].length;
} // result -> ['2', '3', '4']

// XRegExp.replace allows named backreferences in replacements
XRegExp.replace('2012-02-22', date, '${month}/${day}/${year}'); // -> '02/22/2012'
XRegExp.replace('2012-02-22', date, function (match) {
    return match.month + '/' + match.day + '/' +match.year;
}); // -> '02/22/2012'

// In fact, all XRegExps are RegExps and work perfectly with native methods
date.test('2012-02-22'); // -> true

// The *only* caveat is that named captures must be referred to using numbered backreferences
'2012-02-22'.replace(date, '$2/$3/$1'); // -> '02/22/2012'

// If you want, you can extend native methods so you don't have to worry about this
// Doing so also fixes numerous browser bugs in the native methods
XRegExp.install('natives');
'2012-02-22'.replace(date, '${month}/${day}/${year}'); // -> '02/22/2012'
'2012-02-22'.replace(date, function (match) {
    return match.month + '/' + match.day + '/' +match.year;
}); // -> '02/22/2012'
date.exec('2012-02-22').day; // -> 22

// Extract every other digit from a string using XRegExp.forEach
XRegExp.forEach("1a2345", /\d/, function (match, i) {
    if (i % 2) this.push(+match[0]);
}, []); // -> [2, 4]

// Get numbers within <b> tags using XRegExp.matchChain
XRegExp.matchChain('1 <b>2</b> 3 <b>4 a 56</b>', [
    XRegExp('(?is)<b>.*?<\\/b>'),
    /\d+/
]); // -> ['2', '4', '56']

// You can also pass forward and return specific backreferences
var html = '<a href="http://xregexp.com/">XRegExp</a>\
            <a href="http://www.google.com/">Google</a>';
XRegExp.matchChain(html, [
    {regex: /<a href="([^"]+)">/i, backref: 1},
    {regex: XRegExp('(?i)^https?://(?<domain>[^/?#]+)'), backref: 'domain'}
]); // -> ['xregexp.com', 'www.google.com']

// XRegExp regexes get call and apply methods
// To demonstrate, let's first create the function we'll be using...
function filter(array, fn) {
    var res = [];
    array.forEach(function (el) {if (fn.call(null, el)) res.push(el);});
    return res;
}
// Now we can filter arrays using functions and regexes
filter(['a', 'ba', 'ab', 'b'], XRegExp('^a')); // -> ['a', 'ab']

These examples should give you an idea of what's possible, but XRegExp has a lot more tricks that aren't shown here. You can even augment XRegExp's regular expression syntax with addons (see below) or write your own. For the full scoop, see API, syntax, flags, and browser fixes.

XRegExp Unicode Base

First include the Unicode Base script:

<script src="xregexp.js"></script>
<script src="addons/unicode/unicode-base.js"></script>

Then you can do this:

var unicodeWord = XRegExp('^\\p{L}+$');
unicodeWord.test('Русский'); // -> true
unicodeWord.test('日本語'); // -> true
unicodeWord.test('العربية'); // -> true

The base script adds \p{L} (and its alias, \p{Letter}), but other Unicode categories, scripts, and blocks require addon packages. Try these next examples after additionally including unicode-scripts.js:

XRegExp('^\\p{Hiragana}+$').test('ひらがな'); // -> true
XRegExp('^[\\p{Latin}\\p{Common}]+$').test('Über Café.'); // -> true

XRegExp uses the Unicode 6.1 character database (released January 2012).

More details: Addons: Unicode.

XRegExp Match Recursive

First include the Match Recursive script:

<script src="xregexp.js"></script>
<script src="addons/matchrecursive.js"></script>

You can then match recursive constructs using XRegExp patterns 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>a <div>nested</div> tag</div> example.';
XRegExp.matchRecursive(str, '<div\\s*>', '</div>', 'gi', {
    valueNames: ['between', 'left', 'match', 'right']
});
// -> [['between', 'Here is ', 0, 8],
// ['left', '<div>', 8, 13],
// ['match', 'a <div>nested</div> tag', 13, 37],
// ['right', '</div>', 36, 42],
// ['between', ' example.', 42, 51]]

// 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: '\\'
});
// -> [['literal', '...', 0, 3],
// ['value', '1', 4, 5],
// ['literal', '\\{', 6, 8],
// ['value', 'function(x,y){return y+x;}', 9, 35]]

// Sticky mode via flag y
str = '<1><<<2>>><3>4<5>';
XRegExp.matchRecursive(str, '<', '>', 'gy');
// -> ['1', '<<2>>', '3']

More details: Addons: Match Recursive.

How to run server-side tests

npm install -g qunit  # needed to run the tests
npm test  # in the xregexp root directory

Changelog

Historical changes: Version history.
Planned changes: Roadmap.

About

Tools: Unicode range generators by Mathias Bynens. Source file concatenator by Bjarke Walling.

All code released under the MIT License.

Fork me to show support, fix, and extend.