core-js vs regenerator-runtime
JavaScript Polyfills and Runtime Libraries
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JavaScript Polyfills and Runtime Libraries

Core-js and regenerator-runtime are essential libraries in modern JavaScript development. Core-js provides polyfills for ECMAScript features, enabling developers to use the latest JavaScript features while maintaining compatibility with older environments. Regenerator-runtime, on the other hand, is specifically designed to support the async/await syntax and generator functions, allowing developers to write asynchronous code in a more readable manner. Together, these libraries enhance the development experience by ensuring that modern JavaScript features are available across various environments, improving code maintainability and performance.

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core-js26,959,78625,4771.33 MB436 days agoMIT
regenerator-runtime03,83427.9 kB812 years agoMIT

Feature Comparison: core-js vs regenerator-runtime

Polyfill Coverage

  • core-js:

    Core-js offers extensive polyfill coverage for ECMAScript features, including ES6, ES7, and beyond. It allows developers to use modern JavaScript features without worrying about compatibility issues in older environments. With core-js, developers can seamlessly integrate features like promises, symbols, and typed arrays into their applications.

  • regenerator-runtime:

    Regenerator-runtime does not provide polyfills for ECMAScript features but focuses on enabling generator functions and async/await syntax. It transforms these features into compatible code that can run in environments that do not natively support them, ensuring that asynchronous programming remains accessible.

Usage Scenario

  • core-js:

    Core-js is suitable for applications that need to support a wide range of browsers, including older versions. It is particularly useful in large-scale applications where developers want to leverage the latest JavaScript features while ensuring a consistent experience across different environments.

  • regenerator-runtime:

    Regenerator-runtime is best used in applications that utilize async/await for handling asynchronous operations. It is particularly beneficial in scenarios where developers want to write cleaner and more maintainable asynchronous code without the complexity of traditional callback patterns.

Performance Impact

  • core-js:

    While core-js provides a vast array of polyfills, it may introduce some performance overhead due to the additional code that needs to be executed. However, this impact is generally minimal compared to the benefits of using modern JavaScript features. Developers should consider the trade-off between compatibility and performance based on their target environments.

  • regenerator-runtime:

    Regenerator-runtime is lightweight and specifically optimized for handling async/await and generator functions. It has a minimal performance impact, making it a suitable choice for applications that require efficient asynchronous code execution without the bloat of unnecessary polyfills.

Learning Curve

  • core-js:

    Core-js is straightforward to use, especially for developers familiar with modern JavaScript. However, understanding when and how to apply polyfills effectively requires some knowledge of ECMAScript standards and browser compatibility issues. Documentation and community support are available to aid in this learning process.

  • regenerator-runtime:

    Regenerator-runtime is relatively easy to integrate into projects, especially for developers already accustomed to async/await syntax. The learning curve is minimal, as it primarily focuses on enabling existing JavaScript features rather than introducing new concepts.

Community and Support

  • core-js:

    Core-js has a large community and is widely used in the JavaScript ecosystem. It is actively maintained, with regular updates to ensure compatibility with the latest ECMAScript standards. Developers can find extensive documentation and community resources to assist with implementation.

  • regenerator-runtime:

    Regenerator-runtime is also well-supported, particularly within projects that utilize Babel for transpiling JavaScript. It benefits from a strong community and is often included as a dependency in projects that require async/await functionality, ensuring that developers have access to support and resources.

How to Choose: core-js vs regenerator-runtime

  • core-js:

    Choose core-js if you need comprehensive polyfills for a wide range of ECMAScript features, including promises, symbols, and various collection types. It is ideal for projects that require backward compatibility with older browsers or environments that do not support the latest JavaScript standards.

  • regenerator-runtime:

    Choose regenerator-runtime if your project heavily relies on async/await or generator functions. It is specifically tailored for handling asynchronous code and is lightweight, making it a good choice for projects that need to manage async operations without the overhead of additional polyfills.

Similar Npm Packages to core-js

core-js is a modular standard library for JavaScript that provides polyfills for ECMAScript features, including ES6, ES7, and beyond. It allows developers to use modern JavaScript features in environments that do not support them natively, ensuring compatibility across different browsers and platforms. With its modular design, developers can selectively include only the polyfills they need, making it a lightweight and efficient choice for polyfilling JavaScript features.

While core-js is a powerful solution for polyfilling, there are alternatives available that also aim to provide similar functionality. Here are a few notable options:

  • babel-polyfill is a package that includes a full set of polyfills for ECMAScript features. It is designed to work seamlessly with Babel, a popular JavaScript compiler that allows developers to use the latest JavaScript syntax and features. babel-polyfill provides a comprehensive solution for ensuring that your code runs in older environments by including all necessary polyfills. However, it is worth noting that babel-polyfill has been deprecated in favor of using core-js directly, as it is more modular and allows for better tree-shaking.
  • es6-shim is another polyfill library that aims to provide compatibility for ECMAScript 6 features in older JavaScript environments. It extends the built-in JavaScript objects and adds support for new features such as promises, symbols, and more. While es6-shim is a solid choice for adding ES6 compatibility, it is less modular than core-js, which means it may include more polyfills than necessary, potentially increasing the bundle size.

For a detailed comparison of these packages, check out the following link: Comparing babel-polyfill vs core-js vs es6-shim.

Similar Npm Packages to regenerator-runtime

regenerator-runtime is a runtime library that enables the use of generator functions and async/await syntax in JavaScript. It is particularly useful for transpiling modern JavaScript code, allowing developers to write asynchronous code in a more readable and maintainable way. While regenerator-runtime is a powerful tool for handling asynchronous programming, there are several alternatives that also provide similar functionalities. Here are a few notable alternatives:

  • async is a utility module that provides powerful functions for working with asynchronous JavaScript. It offers a variety of methods for handling asynchronous operations, such as async.waterfall, async.series, and async.parallel, making it easier to manage complex asynchronous workflows. If you are looking for a comprehensive solution to handle asynchronous control flow without using promises or async/await, async is a great choice.

  • babel-runtime is a library that provides a modular runtime for Babel, which is a popular JavaScript compiler. It includes polyfills and helper functions that allow developers to use modern JavaScript features while maintaining compatibility with older environments. If you are already using Babel for transpiling your code and want to ensure that your async/await syntax works seamlessly across different environments, babel-runtime can be a useful addition.

  • bluebird is a fully-featured promise library that focuses on performance and features. It provides a rich set of methods for working with promises, including advanced features like cancellation, progress tracking, and more. If you need a powerful promise library that goes beyond the native Promise implementation, bluebird is an excellent option.

  • core-js is a modular standard library for JavaScript that includes polyfills for many modern JavaScript features, including those related to promises and async/await. It is often used in conjunction with Babel to ensure that modern JavaScript code runs smoothly in older environments. If you want a comprehensive set of polyfills for various JavaScript features, core-js is a solid choice.

  • rxjs is a library for reactive programming using Observables, which makes it easy to compose asynchronous and event-based programs. It provides a powerful set of operators for handling asynchronous data streams, making it suitable for complex applications that require reactive programming patterns. If you are building applications that heavily rely on event-driven architecture or need to manage multiple asynchronous data streams, rxjs is a great fit.

To see how regenerator-runtime compares with async, babel-runtime, bluebird, core-js, and rxjs, check out the comparison: Comparing async vs babel-runtime vs bluebird vs core-js vs regenerator-runtime vs rxjs.

README for core-js

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fundraising PRs welcome version core-js downloads

I highly recommend reading this: So, what's next?

core-js is a modular standard library for JavaScript. Includes polyfills for ECMAScript up to 2026: promises, symbols, collections, iterators, typed arrays, many other features, ECMAScript proposals, some cross-platform WHATWG / W3C features and proposals like URL. You can load only required features or use it without global namespace pollution.

Raising funds

core-js isn't backed by a company, so the future of this project depends on you. Become a sponsor or a backer if you are interested in core-js: Open Collective, Patreon, Boosty, Bitcoin ( bc1qlea7544qtsmj2rayg0lthvza9fau63ux0fstcz ), Alipay.

Example of usage:

import 'core-js/actual';

Promise.try(() => 42).then(it => console.log(it)); // => 42

Array.from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

[1, 2].flatMap(it => [it, it]); // => [1, 1, 2, 2]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

You can load only required features:

import 'core-js/actual/promise';
import 'core-js/actual/set';
import 'core-js/actual/iterator';
import 'core-js/actual/array/from';
import 'core-js/actual/array/flat-map';
import 'core-js/actual/structured-clone';

Promise.try(() => 42).then(it => console.log(it)); // => 42

Array.from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

[1, 2].flatMap(it => [it, it]); // => [1, 1, 2, 2]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

Or use it without global namespace pollution:

import Promise from 'core-js-pure/actual/promise';
import Set from 'core-js-pure/actual/set';
import Iterator from 'core-js-pure/actual/iterator';
import from from 'core-js-pure/actual/array/from';
import flatMap from 'core-js-pure/actual/array/flat-map';
import structuredClone from 'core-js-pure/actual/structured-clone';

Promise.try(() => 42).then(it => console.log(it)); // => 42

from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

flatMap([1, 2], it => [it, it]); // => [1, 1, 2, 2]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

It's a global version (first 2 examples), for more info see core-js documentation.

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