@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

v7.24.4 (2024-04-03)

:eyeglasses: Spec Compliance

• babel-parser
  • #16403 Forbid initializerless using (@JLHwung)
• babel-helpers, babel-plugin-proposal-decorators, babel-runtime-corejs3
  • #16388 Ensure decorators are callable (@JLHwung)

:bug: Bug Fix

• babel-generator
  • #16402 fix: Correctly prints { [key in Bar]? } (@liuxingbaoyu)
  • #16394 fix: Correctly generate TSMappedType (@liuxingbaoyu)
• babel-compat-data, babel-plugin-bugfix-firefox-class-in-computed-class-key, babel-preset-env
  • #16390 Create bugfix plugin for classes in computed keys in Firefox (@nicolo-ribaudo)
• babel-helper-create-class-features-plugin, babel-plugin-proposal-decorators
  • #16387 fix: support mutated outer decorated class binding (@JLHwung)
  • #16385 fix: Decorators when super() exists and protoInit is not needed (@liuxingbaoyu)
• babel-plugin-transform-block-scoping
  • #16384 fix: Transform scoping for for X in loop (@liuxingbaoyu)
  • #16368 fix: Capture let when the for body is not a block (@liuxingbaoyu)
• babel-core, babel-plugin-transform-block-scoped-functions, babel-plugin-transform-block-scoping
  • #16363 Fix incorrect function hoisting in some case statements (@luiscubal)