@babel/runtime-corejs2

What is @babel/runtime-corejs2?

@babel/runtime-corejs2 is a library that provides a runtime for Babel that includes polyfills for ECMAScript features using core-js@2. It helps to avoid code duplication and reduce the size of the compiled code by providing helpers and polyfills as separate modules.

What are @babel/runtime-corejs2's main functionalities?

Polyfilling ECMAScript features

This feature allows you to polyfill ECMAScript features like Map and Set, ensuring compatibility with older environments that do not support these features natively.

import 'core-js/es6/map';
import 'core-js/es6/set';

const map = new Map();
const set = new Set();

Helper functions

This feature provides helper functions like classCallCheck to ensure that classes are instantiated correctly, which is useful for maintaining compatibility with older JavaScript environments.

import _classCallCheck from '@babel/runtime-corejs2/helpers/classCallCheck';

class MyClass {
  constructor() {
    _classCallCheck(this, MyClass);
  }
}

Async/Await support

This feature provides support for async/await syntax by transforming it into generator functions, which are compatible with older JavaScript environments.

import _asyncToGenerator from '@babel/runtime-corejs2/helpers/asyncToGenerator';
import regeneratorRuntime from 'regenerator-runtime';

const asyncFunction = _asyncToGenerator(function* () {
  const result = yield fetch('https://api.example.com/data');
  return result.json();
});

asyncFunction().then(data => console.log(data));

Other packages similar to @babel/runtime-corejs2

@babel/runtime

@babel/runtime is a similar package that provides the same runtime helpers and polyfills but uses core-js@3 instead of core-js@2. It is more up-to-date and recommended for new projects.

core-js

core-js is a modular standard library for JavaScript that includes polyfills for ECMAScript features. It can be used directly to polyfill features without relying on Babel's runtime.

regenerator-runtime

regenerator-runtime is a runtime library for transforming generator functions and async/await syntax. It is often used in conjunction with Babel to provide support for these features in older environments.

README

@babel/runtime-corejs2

babel's modular runtime helpers with core-js@2 polyfilling

See our website @babel/runtime-corejs2 for more information.

Install

Using npm:

npm install --save @babel/runtime-corejs2

or using yarn:

yarn add @babel/runtime-corejs2

Changelog

v7.26.0 (2024-10-25)

:rocket: New Feature

• babel-core, babel-generator, babel-parser, babel-plugin-syntax-import-assertions, babel-plugin-syntax-import-attributes, babel-preset-env, babel-standalone, babel-types
  • #16850 Enable import attributes parsing by default (@nicolo-ribaudo)
• babel-core
  • #16862 feat: support async plugin's pre/post (@timofei-iatsenko)
• babel-compat-data, babel-plugin-proposal-regexp-modifiers, babel-plugin-transform-regexp-modifiers, babel-preset-env, babel-standalone
  • #16692 Add transform-regexp-modifiers to preset-env (@JLHwung)
• babel-parser
  • #16849 feat: add startIndex parser option (@DylanPiercey)
• babel-generator, babel-parser, babel-plugin-syntax-flow
  • #16841 Always enable parsing of Flow enums (@nicolo-ribaudo)
• babel-helpers, babel-preset-typescript, babel-runtime-corejs3
  • #16794 Support import() in rewriteImportExtensions (@liuxingbaoyu)
• babel-generator, babel-parser
  • #16708 Add experimental format-preserving mode to @babel/generator (@nicolo-ribaudo)

:bug: Bug Fix

• babel-core
  • #16928 Workaround Node.js bug for parallel loading of TLA modules (@nicolo-ribaudo)
  • #16926 Fix loading of modules with TLA in Node.js 23 (@nicolo-ribaudo)

:nail_care: Polish

• babel-plugin-proposal-json-modules, babel-plugin-transform-json-modules, babel-standalone
  • #16924 Rename proposal-json-modules to transform-json-modules (@nicolo-ribaudo)

:house: Internal

• babel-code-frame, babel-highlight
  • #16896 Inline @babel/highlight in @babel/code-frame (@nicolo-ribaudo)
• babel-generator, babel-parser, babel-types
  • #16732 Add kind to TSModuleDeclaration (@liuxingbaoyu)

:running_woman: Performance

• babel-helper-module-transforms, babel-plugin-transform-modules-commonjs
  • #16882 perf: Improve module transforms (@liuxingbaoyu)