XRegExp 5.1.0 for DENO

This a port of the XRegExp source files to Deno. Deno can load and use these source files directly and only a few trivial changes were needed to make that work, things like adding file extensions when importing modules and changing the exports statements to fit the Deno syntax as opposed to Node’s module.exports syntax.

Deno Testing:

I have done a test of all the usage examples in this README file (see the test directory), basically choosing to relay on the extensive testing done in the original Node package.

XRegExp 5.1.0

XRegExp provides augmented (and extensible) JavaScript regular expressions. You get modern syntax and flags beyond what browsers support natively. XRegExp is also a regex utility belt with tools to make your grepping and parsing easier, while freeing you from regex cross-browser inconsistencies and other annoyances.

XRegExp supports all native ES6 regular expression syntax. It supports ES5+ browsers, and you can use it with Node.js or as a RequireJS module. Over the years, many of XRegExp’s features have been adopted by new JavaScript standards (named capturing, Unicode properties/scripts/categories, flag s, sticky matching, etc.), so using XRegExp can be a way to extend these features into older browsers.

Performance

XRegExp compiles to native RegExp objects. Therefore regexes built with XRegExp perform just as fast as native regular expressions. There is a tiny extra cost when compiling a pattern for the first time.

Installation and usage

In Deno:

// @deno-types='https://deno.land/x/xregexp/types/index.d.ts'
import XRegExp from  'https://deno.land/x/xregexp/src/index.js'

If you are not using TypeScript then leave out the @deno-types import above.

Usage examples

// Using named capture and flag x for free-spacing and line comments
const date = XRegExp(
    `(?<year>  [0-9]{4} ) -?  # year
     (?<month> [0-9]{2} ) -?  # month
     (?<day>   [0-9]{2} )     # day`, 'x');

// XRegExp.exec provides named backreferences on the result's groups property
let match = XRegExp.exec('2021-02-22', date);
match.groups.year; // -> '2021'

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

// XRegExp.replace allows named backreferences in replacements
XRegExp.replace('2021-02-22', date, '$<month>/$<day>/$<year>');
// -> '02/22/2021'
XRegExp.replace('2021-02-22', date, (...args) => {
    // Named backreferences are on the last argument
    const groups = args[args.length - 1];
    return `${groups.month}/${groups.day}/${groups.year}`;
});
// -> '02/22/2021'

// XRegExps compile to RegExps and work with native methods
date.test('2021-02-22');
// -> true
// However, named captures must be referenced using numbered backreferences
// if used with native methods
'2021-02-22'.replace(date, '$2/$3/$1');
// -> '02/22/2021'

// Use XRegExp.forEach to extract every other digit from a string
const evens = [];
XRegExp.forEach('1a2345', /\d/, (match, i) => {
    if (i % 2) evens.push(+match[0]);
});
// evens -> [2, 4]

// Use XRegExp.matchChain to get numbers within <b> tags
XRegExp.matchChain('1 <b>2</b> 3 <B>4 \n 56</B>', [
    XRegExp('<b>.*?</b>', 'is'),
    /\d+/
]);
// -> ['2', '4', '56']

// You can also pass forward and return specific backreferences
const html =
    `<a href="https://xregexp.com/">XRegExp</a>
     <a href="https://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']

// Merge strings and regexes, with updated backreferences
XRegExp.union(['m+a*n', /(bear)\1/, /(pig)\1/], 'i', {conjunction: 'or'});
// -> /m\+a\*n|(bear)\1|(pig)\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 also augment XRegExp’s regular expression syntax with addons (see below) or write your own. See xregexp.com for details.

Unicode

XRegExp supports Unicode, so you can do great things like this:

// Test some Unicode scripts
// Can also use the Script= prefix to match ES2018: \p{Script=Hiragana}
XRegExp('^\\p{Hiragana}+$').test('ひらがな'); // -> true
XRegExp('^[\\p{Latin}\\p{Common}]+$').test('Über Café.'); // -> true

// Test the Unicode categories Letter and Mark
// Can also use the short names \p{L} and \p{M}
const unicodeWord = XRegExp.tag()`^\p{Letter}[\p{Letter}\p{Mark}]*$`;
unicodeWord.test('Русский'); // -> true
unicodeWord.test('日本語'); // -> true
unicodeWord.test('العربية'); // -> 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. 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('^\\p{S}$').test('💩'); // -> false
XRegExp('^\\p{S}$', 'A').test('💩'); // -> true
// Using surrogate pair U+D83D U+DCA9 to represent U+1F4A9 (pile of poo)
XRegExp('^\\p{S}$', 'A').test('\uD83D\uDCA9'); // -> true

// Implicit flag A
XRegExp.install('astral');
XRegExp('^\\p{S}$').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 14.0.0.

XRegExp.build

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

const time = XRegExp.build('(?x)^ {{hours}} ({{minutes}}) $', {
    hours: XRegExp.build('{{h12}} : | {{h24}}', {
        h12: /1[0-2]|0?[1-9]/,
        h24: /2[0-3]|[01][0-9]/
    }),
    minutes: /^[0-5][0-9]$/
});

time.test('10:59'); // -> true
XRegExp.exec('10:59', time).groups.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.

XRegExp.tag (included with XRegExp.build)

Provides tagged template literals that create regexes with XRegExp syntax and flags:

XRegExp.tag()`\b\w+\b`.test('word'); // -> true

const hours = /1[0-2]|0?[1-9]/;
const minutes = /(?<minutes>[0-5][0-9])/;
const time = XRegExp.tag('x')`\b <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mrow><mi>h</mi><mi>o</mi><mi>u</mi><mi>r</mi><mi>s</mi></mrow><mo>:</mo></mrow><annotation encoding="application/x-tex">{hours} : </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord"><span class="mord mathnormal">h</span><span class="mord mathnormal">o</span><span class="mord mathnormal">u</span><span class="mord mathnormal">rs</span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">:</span></span></span></span>{minutes} \b`;
time.test('10:59'); // -> true
XRegExp.exec('10:59', time).groups.minutes; // -> '59'

const backref1 = /(a)\1/;
const backref2 = /(b)\1/;
XRegExp.tag()`${backref1}${backref2}`.test('aabb'); // -> true

XRegExp.tag does more than just interpolation. You get all the XRegExp syntax and flags, and since it reads patterns as raw strings, you no longer need to escape all your backslashes. XRegExp.tag also uses XRegExp.build under the hood, so you get all of its extras for free. Leading ^ and trailing unescaped $ are stripped from interpolated patterns if both are present (to allow embedding independently useful anchored regexes), interpolating into a character class is an error (to avoid unintended meaning in edge cases), interpolated patterns are treated as atomic units when quantified, interpolated strings have their special characters escaped, and any backreferences within an interpolated regex are rewritten to work within the overall pattern.

XRegExp.matchRecursive

A robust and flexible API for matching recursive constructs using XRegExp pattern strings as left and right delimiters:

const str1 = '(t((e))s)t()(ing)';
XRegExp.matchRecursive(str1, '\\(', '\\)', 'g');
// -> ['t((e))s', '', 'ing']

// Extended information mode with valueNames
const str2 = 'Here is <div> <div>an</div></div> example';
XRegExp.matchRecursive(str2, '<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
const str3 = '...{1}.\\{{function(x,y){return {y:x}}}';
XRegExp.matchRecursive(str3, '{', '}', '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
const str4 = '<1><<<2>>><3>4<5>';
XRegExp.matchRecursive(str4, '<', '>', 'gy');
// -> ['1', '<<2>>', '3']

// Skipping unbalanced delimiters instead of erroring
const str5 = 'Here is <div> <div>an</div> unbalanced example';
XRegExp.matchRecursive(str5, '<div\\s*>', '</div>', 'gi', {
    unbalanced: 'skip'
});
// -> ['an']

By default, XRegExp.matchRecursive throws an error if it scans past an unbalanced delimiter in the target string. Multiple alternative options are available for handling unbalanced delimiters.

Credits

The XRegExp project on node.js collaborators are:

Thanks to all contributors and others who have submitted code, provided feedback, reported bugs, and inspired new features.

XRegExp is released under the MIT License. Learn more at xregexp.com.