// 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']

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

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

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']