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https://github.com/mathiasbynens/regexpu

A source code transpiler that enables the use of ES2015 Unicode regular expressions in ES5.
https://github.com/mathiasbynens/regexpu

code-generation ecmascript es2015 javascript regex regexp regular-expression unicode

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A source code transpiler that enables the use of ES2015 Unicode regular expressions in ES5.

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# regexpu [![Build status](https://travis-ci.org/mathiasbynens/regexpu.svg?branch=main)](https://travis-ci.org/mathiasbynens/regexpu) [![Code coverage status](https://img.shields.io/codecov/c/github/mathiasbynens/regexpu.svg)](https://codecov.io/gh/mathiasbynens/regexpu) [![regexpu on npm](https://img.shields.io/npm/v/regexpu)](https://www.npmjs.com/package/regexpu)



_regexpu_ is a source code transpiler that enables the use of ES2015 Unicode regular expressions in JavaScript-of-today (ES5). It rewrites regular expressions that make use of [the ES2015 `u` flag](https://mathiasbynens.be/notes/es6-unicode-regex) into equivalent ES5-compatible regular expressions.



[Here’s an online demo.](https://mothereff.in/regexpu)



[Traceur v0.0.61+](https://github.com/google/traceur-compiler), [Babel v1.5.0+](https://github.com/babel/babel), [esnext v0.12.0+](https://github.com/esnext/esnext), and [Bublé v0.12.0+](https://buble.surge.sh/) use _regexpu_ for their `u` regexp transpilation. The REPL demos for [Traceur](https://google.github.io/traceur-compiler/demo/repl.html#%2F%2F%20Traceur%20now%20uses%20regexpu%20%28https%3A%2F%2Fmths.be%2Fregexpu%29%20to%20transpile%20regular%0A%2F%2F%20expression%20literals%20that%20have%20the%20ES2015%20%60u%60%20flag%20set%20into%20equivalent%20ES5.%0A%0A%2F%2F%20Match%20any%20symbol%20from%20U%2B1F4A9%20PILE%20OF%20POO%20to%20U%2B1F4AB%20DIZZY%20SYMBOL.%0Avar%20regex%20%3D%20%2F%5B%F0%9F%92%A9-%F0%9F%92%AB%5D%2Fu%3B%20%2F%2F%20Or%2C%20%60%2F%5Cu%7B1F4A9%7D-%5Cu%7B1F4AB%7D%2Fu%60.%0Aconsole.log%28%0A%20%20regex.test%28'%F0%9F%92%A8'%29%2C%20%2F%2F%20false%0A%20%20regex.test%28'%F0%9F%92%A9'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AA'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AB'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AC'%29%20%20%2F%2F%20false%0A%29%3B%0A%0A%2F%2F%20See%20https%3A%2F%2Fmathiasbynens.be%2Fnotes%2Fes6-unicode-regex%20for%20more%20examples%20and%0A%2F%2F%20info.%0A), [Babel](https://babeljs.io/repl/#?experimental=true&playground=true&evaluate=true&code=%2F%2F%20Babel%20now%20uses%20regexpu%20%28https%3A%2F%2Fmths.be%2Fregexpu%29%20to%20transpile%20regular%0A%2F%2F%20expression%20literals%20that%20have%20the%20ES2015%20%60u%60%20flag%20set%20into%20equivalent%20ES5.%0A%0A%2F%2F%20Match%20any%20symbol%20from%20U%2B1F4A9%20PILE%20OF%20POO%20to%20U%2B1F4AB%20DIZZY%20SYMBOL.%0Avar%20regex%20%3D%20%2F%5B%F0%9F%92%A9-%F0%9F%92%AB%5D%2Fu%3B%20%2F%2F%20Or%2C%20%60%2F%5Cu%7B1F4A9%7D-%5Cu%7B1F4AB%7D%2Fu%60.%0Aconsole.log%28%0A%20%20regex.test%28'%F0%9F%92%A8'%29%2C%20%2F%2F%20false%0A%20%20regex.test%28'%F0%9F%92%A9'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AA'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AB'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AC'%29%20%20%2F%2F%20false%0A%29%3B%0A%0A%2F%2F%20See%20https%3A%2F%2Fmathiasbynens.be%2Fnotes%2Fes6-unicode-regex%20for%20more%20examples%20and%0A%2F%2F%20info.%0A), [esnext](https://esnext.github.io/esnext/#%2F%2F%20esnext%20now%20uses%20regexpu%20%28https%3A%2F%2Fmths.be%2Fregexpu%29%20to%20transpile%20regular%0A%2F%2F%20expression%20literals%20that%20have%20the%20ES2015%20%60u%60%20flag%20set%20into%20equivalent%20ES5.%0A%0A%2F%2F%20Match%20any%20symbol%20from%20U%2B1F4A9%20PILE%20OF%20POO%20to%20U%2B1F4AB%20DIZZY%20SYMBOL.%0Avar%20regex%20%3D%20%2F%5B%F0%9F%92%A9-%F0%9F%92%AB%5D%2Fu%3B%20%2F%2F%20Or%2C%20%60%2F%5Cu%7B1F4A9%7D-%5Cu%7B1F4AB%7D%2Fu%60.%0Aconsole.log%28%0A%20%20regex.test%28'%F0%9F%92%A8'%29%2C%20%2F%2F%20false%0A%20%20regex.test%28'%F0%9F%92%A9'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AA'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AB'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AC'%29%20%20%2F%2F%20false%0A%29%3B%0A%0A%2F%2F%20See%20https%3A%2F%2Fmathiasbynens.be%2Fnotes%2Fes6-unicode-regex%20for%20more%20examples%20and%0A%2F%2F%20info.%0A), and [Bublé](https://buble.surge.sh/#%2F%2F%20Bubl%C3%A9%20now%20uses%20regexpu%20%28https%3A%2F%2Fmths.be%2Fregexpu%29%20to%20transpile%20regular%0A%2F%2F%20expression%20literals%20that%20have%20the%20ES2015%20%60u%60%20flag%20set%20into%20equivalent%20ES5.%0A%0A%2F%2F%20Match%20any%20symbol%20from%20U%2B1F4A9%20PILE%20OF%20POO%20to%20U%2B1F4AB%20DIZZY%20SYMBOL.%0Avar%20regex%20%3D%20%2F%5B%F0%9F%92%A9-%F0%9F%92%AB%5D%2Fu%3B%20%2F%2F%20Or%2C%20%60%2F%5Cu%7B1F4A9%7D-%5Cu%7B1F4AB%7D%2Fu%60.%0Aconsole.log%28%0A%20%20regex.test%28'%F0%9F%92%A8'%29%2C%20%2F%2F%20false%0A%20%20regex.test%28'%F0%9F%92%A9'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AA'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AB'%29%2C%20%2F%2F%20true%0A%20%20regex.test%28'%F0%9F%92%AC'%29%20%20%2F%2F%20false%0A%29%3B%0A%0A%2F%2F%20See%20https%3A%2F%2Fmathiasbynens.be%2Fnotes%2Fes6-unicode-regex%20for%20more%20examples%0A%2F%2F%20and%20info.%0A) let you try `u` regexps as well as other ES.next features.



## Example



Consider a file named `example-es2015.js` with the following contents:



```js

var string = 'foo💩bar';

var match = string.match(/foo(.)bar/u);

console.log(match[1]);

// → '💩'



// This regex matches any symbol from U+1F4A9 to U+1F4AB, and nothing else.

var regex = /[\u{1F4A9}-\u{1F4AB}]/u;

// The following regex is equivalent.

var alternative = /[💩-💫]/u;

console.log([

  regex.test('a'),  // false

  regex.test('💩'), // true

  regex.test('💪'), // true

  regex.test('💫'), // true

  regex.test('💬')  // false

]);

```



Let’s transpile it:



```bash

$ regexpu < example-es2015.js > example-es5.js

```



`example-es5.js` can now be used in ES5 environments. Its contents are as follows:



```js

var string = 'foo💩bar';

var match = string.match(/foo((?:[\0-\t\x0B\f\x0E-\u2027\u202A-\uD7FF\uE000-\uFFFF]|[\uD800-\uDBFF][\uDC00-\uDFFF]|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?:[^\uD800-\uDBFF]|^)[\uDC00-\uDFFF]))bar/);

console.log(match[1]);

// → '💩'



// This regex matches any symbol from U+1F4A9 to U+1F4AB, and nothing else.

var regex = /(?:\uD83D[\uDCA9-\uDCAB])/;

// The following regex is equivalent.

var alternative = /(?:\uD83D[\uDCA9-\uDCAB])/;

console.log([

  regex.test('a'),  // false

  regex.test('💩'), // true

  regex.test('💪'), // true

  regex.test('💫'), // true

  regex.test('💬')  // false

]);

```



## Known limitations



1. _regexpu_ only transpiles regular expression _literals_, so things like `RegExp('…', 'u')` are not affected.

2. _regexpu_ doesn’t polyfill [the `RegExp.prototype.unicode` getter](https://mths.be/es6#sec-get-regexp.prototype.unicode) because it’s not possible to do so without side effects.

3. _regexpu_ doesn’t support [canonicalizing the contents of back-references in regular expressions with both the `i` and `u` flag set](https://github.com/mathiasbynens/regexpu/issues/4), since that would require transpiling/wrapping strings.

4. _regexpu_ [doesn’t match lone low surrogates accurately](https://github.com/mathiasbynens/regexpu/issues/17). Unfortunately that is impossible to implement due to the lack of lookbehind support in JavaScript regular expressions.



## Installation



To use _regexpu_ programmatically, install it as a dependency via [npm](https://www.npmjs.com/):



```bash

npm install regexpu --save-dev

```



To use the command-line interface, install _regexpu_ globally:



```bash

npm install regexpu -g

```



## API



### `regexpu.version`



A string representing the semantic version number.



### `regexpu.rewritePattern(pattern, flags, options)`



This is an alias for the `rewritePattern` function exported by [_regexpu-core_](https://github.com/mathiasbynens/regexpu-core). Please refer to that project’s documentation for more information.



`regexpu.rewritePattern` uses [regjsgen](https://github.com/d10/regjsgen), [regjsparser](https://github.com/jviereck/regjsparser), and [regenerate](https://github.com/mathiasbynens/regenerate) as internal dependencies. If you only need this function in your program, it’s better to include it directly:



```js

// Instead of…

const rewritePattern = require('regexpu').rewritePattern;



// Use this:

const rewritePattern = require('regexpu-core');

```



This prevents the [Recast](https://github.com/benjamn/recast) and [Esprima](https://github.com/ariya/esprima) dependencies from being loaded into memory.



### `regexpu.transformTree(ast, options)` or its alias `regexpu.transform(ast, options)`



This function accepts an abstract syntax tree representing some JavaScript code, and returns a transformed version of the tree in which any regular expression literals that use the ES2015 `u` flag are rewritten in ES5.



```js

const regexpu = require('regexpu');

const recast = require('recast');

const tree = recast.parse(code); // ES2015 code

const transformedTree = regexpu.transform(tree);

const result = recast.print(transformedTree);

console.log(result.code); // transpiled ES5 code

console.log(result.map); // source map

```



The optional `options` object is passed to _regexpu-core_’s `rewritePattern`. For a description of the available options, [see its documentation](https://github.com/mathiasbynens/regexpu-core#rewritepatternpattern-flags-options).



`regexpu.transformTree` uses [Recast](https://github.com/benjamn/recast), [regjsgen](https://github.com/d10/regjsgen), [regjsparser](https://github.com/jviereck/regjsparser), and [regenerate](https://github.com/mathiasbynens/regenerate) as internal dependencies. If you only need this function in your program, it’s better to include it directly:



```js

const transformTree = require('regexpu/transform-tree');

```



This prevents the [Esprima](https://github.com/ariya/esprima) dependency from being loaded into memory.



### `regexpu.transpileCode(code, options)`



This function accepts a string representing some JavaScript code, and returns a transpiled version of this code tree in which any regular expression literals that use the ES2015 `u` flag are rewritten in ES5.



```js

const es2015 = 'console.log(/foo.bar/u.test("foo💩bar"));';

const es5 = regexpu.transpileCode(es2015);

// → 'console.log(/foo(?:[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uD7FF\\uDC00-\\uFFFF]|[\\uD800-\\uDBFF][\\uDC00-\\uDFFF]|[\\uD800-\\uDBFF])bar/.test("foo💩bar"));'

```



The optional `options` object recognizes the following properties:



* `sourceFileName`: a string representing the file name of the original ES2015 source file.

* `sourceMapName`: a string representing the desired file name of the source map.

* `dotAllFlag`: a boolean indicating whether to enable [experimental support for the `s` (`dotAll`) flag](https://github.com/mathiasbynens/es-regexp-dotall-flag).

* `unicodePropertyEscape`: a boolean indicating whether to enable [experimental support for Unicode property escapes](https://github.com/mathiasbynens/regexpu-core/blob/master/property-escapes.md).



The `sourceFileName` and `sourceMapName` properties must be provided if you want to generate source maps.



```js

const result = regexpu.transpileCode(code, {

  'sourceFileName': 'es2015.js',

  'sourceMapName': 'es2015.js.map',

});

console.log(result.code); // transpiled source code

console.log(result.map); // source map

```



`regexpu.transpileCode` uses [Esprima](https://github.com/ariya/esprima), [Recast](https://github.com/benjamn/recast), [regjsgen](https://github.com/d10/regjsgen), [regjsparser](https://github.com/jviereck/regjsparser), and [regenerate](https://github.com/mathiasbynens/regenerate) as internal dependencies. If you only need this function in your program, feel free to include it directly:



```js

const transpileCode = require('regexpu/transpile-code');

```



## Transpilers that use regexpu internally



If you’re looking for a general-purpose ES.next-to-ES5 transpiler with support for Unicode regular expressions, consider using one of these:



* [Traceur](https://github.com/google/traceur-compiler) v0.0.61+

* [Babel](https://github.com/babel/babel) v1.5.0+

* [esnext](https://github.com/esnext/esnext) v0.12.0+

* [Bublé](https://gitlab.com/Rich-Harris/buble) v0.12.0+



## For maintainers



### How to publish a new release



1. On the `main` branch, bump the version number in `package.json`:



    ```sh

    npm version patch -m 'Release v%s'

    ```



    Instead of `patch`, use `minor` or `major` [as needed](https://semver.org/).



    Note that this produces a Git commit + tag.



1. Push the release commit and tag:



    ```sh

    git push && git push --tags

    ```



    Our CI then automatically publishes the new release to npm.



## Author



| [![twitter/mathias](https://gravatar.com/avatar/24e08a9ea84deb17ae121074d0f17125?s=70)](https://twitter.com/mathias "Follow @mathias on Twitter") |

|---|

| [Mathias Bynens](https://mathiasbynens.be/) |



## License



_regexpu_ is available under the [MIT](https://mths.be/mit) license.