This is a Babel plugin that transpiles tagged Regex+ regex templates into native RegExp literals, enabling syntax for modern and more readable regex features (atomic groups, subroutines, insignificant whitespace, comments, etc.) without the need for calling regex at runtime. Although Regex+ is already a lightweight and high-performance library, this takes things further by giving you its developer experience benefits without adding any runtime dependencies and without users paying any runtime cost.
Input:
const ipv4 = regex`
^ \g<byte> (\.\g<byte>){3} $
(?(DEFINE)
(?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d)
)
`;
Output:
const ipv4 = /^(?:2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d)(?:\.(?:2[0-4]\d|25[0-5]|1\d\d|[1-9]?\d)){3}$/v;
The following call formats are all supported:
regex`<expression>`regex()`<expression>`regex('<flags>')`<expression>`regex({<options>})`<expression>`Interpolation into the expression is supported, so long as the interpolated values are:
RegExp or new RegExp with string values.pattern`â¦` as a template tag (without interpolation) or pattern(â¦) as a function call with a string or number literal as the value.Additional details:
'â¦', "â¦", `â¦`, and String.raw`â¦` can all be used, so long as they don't include interpolation.regex templates that interpolate variables or other dynamic values are not transformed.regex options subclass, plugins, and unicodeSetsPlugin are unsupported. Regexes that use these options are not transformed.regex tag as a function instead of with backticks is not transformed.The following options are available when running the Babel plugin:
removeImport â If true, removes any import declarations with module name 'regex'.disableUnicodeSets â If true, adds regex option disable: {v: true} to all regexes before transformation.headerComment â If given a value, it will be added in a comment at the top of processed output/files.optimize (experimental) â If true, attempts to optimize/shorten the regex source generated by regex.
By default, the regex tag implicitly adds flag v (unicodeSets, supported by Node.js 20 and 2023-era browsers) to generated regexes, but it automatically switches to flag u (while applying v's escaping rules) in environments without native v support. This creates an issue for the Babel plugin, because although it will typically be run in environments that support flag v, the transpiled results may need to run for users in old browsers without native v.
There are several ways to address this:
disableUnicodeSets: true (see details above).regex option regex({disable: {v: true}})`â¦` in your code.You can try all of these options in the demo REPL.
Add this plugin and a recent version of Babel (tested with 7.24â7.26) to your project:
npm install --save-dev @babel/core @babel/cli npm install --save-dev babel-plugin-transform-regex
Run the following command to compile all of your code from the src directory to lib:
./node_modules/.bin/babel src --out-dir lib --plugins=babel-plugin-transform-regex
To make this easier to run, create a config file in the root of your project named babel.config.json, with this content:
{
"plugins": ["babel-plugin-transform-regex"]
}
Or to set plugin options:
{
"plugins": [["babel-plugin-transform-regex", {"removeImport": true}]]
}
If you're using TypeScript, also add @babel/plugin-syntax-typescript.
Then add a script to your package.json to run the build:
"scripts": {
"build": "babel src --out-dir lib"
}
After that, you can run it via npm run build.
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