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@babel/plugin-transform-duplicate-named-capturing-groups-regex

info

This plugin is included in @babel/preset-env, in ES2025.

This plugin transforms regular expression literals to support duplicate named capturing groups. It does not patch the new RegExp constructor, since its arguments cannot be pre-transformed statically: to handle runtime behavior of functions/classes, you will need to use a polyfill instead.

Examples​

In

JavaScript
var re = /(?<year>\d{4})-(?<month>\d{2})|(?<month>\d{2})-(?<year>\d{4})/;

console.log(re.exec("02-1999").groups.year);

Out

JavaScript
var re = _wrapRegExp(/(\d{4})-(\d{2})|(\d{2})-(\d{4})/, {
  year: [1, 4],
  month: [2, 3],
});

console.log(re.exec("02-1999").groups.year);

Installation​

npm install --save-dev @babel/plugin-transform-duplicate-named-capturing-groups-regex

Usage​

babel.config.json
{
  "plugins": ["@babel/plugin-transform-duplicate-named-capturing-groups-regex"]
}

Via CLI​

Shell
babel --plugins @babel/plugin-transform-duplicate-named-capturing-groups-regex script.js

Via Node API​

JavaScript
require("@babel/core").transformSync("code", {
  plugins: ["@babel/plugin-transform-duplicate-named-capturing-groups-regex"],
});

Options​

runtime​

boolean, defaults to true

When this option is disabled, Babel doesn't wrap RegExps with the _wrapRegExp helper. The output only supports internal group references, and not runtime properties:

JavaScript
var stringRe = /(?:(?<quote>")|(?<quote>')).*?\k<quote>/;

stringRe.test("'foo'"); // "true", works
stringRe.exec("'foo'").groups.quote; // undefined
tip

You can read more about configuring plugin options here

References​