ES6 shim
A collection of JavaScript polyfills and shims for web platform features, enabling future-looking code across browsers.
What is ES6 shim?
Polyfill is a collection of JavaScript polyfills and shims that implement web platform features in browsers that lack native support. It enables developers to use modern ECMAScript and Web APIs while maintaining compatibility with older browsers. The project covers standards from HTML and DOM to Fetch and URL APIs, providing modular scripts for incremental adoption.
Frontend developers and web engineers who need to support legacy browsers while using modern JavaScript and web standards in their projects.
Developers choose Polyfill for its pragmatic approach to browser compatibility, offering a curated set of polyfills that are actually used in production. It avoids over-engineering by not aiming for 100% spec compliance, focusing instead on practical gaps that matter for real-world code.
Overview
JavaScript Polyfills, Shims and More
Use Cases
Best For
- Adding support for ES2015+ features in older browsers
- Implementing the Fetch API in environments without native support
- Using modern DOM methods like querySelector in IE7 and IE8
- Enabling HTML5 features like dataset and classList in legacy Internet Explorer
- Polyfilling the URL API for consistent URL parsing and manipulation
- Ensuring consistent animation timing with requestAnimationFrame in older browsers
Not Ideal For
- Projects targeting only modern browsers (e.g., Chrome 80+, Firefox 70+) where polyfills add unnecessary overhead and bloat.
- Node.js applications or server-side environments, as the project explicitly states it's not packaged as Node.js modules and focuses solely on browser APIs.
- Teams using advanced build tools (like Webpack or Rollup) that require fine-grained, tree-shakable polyfills, since the bundled versions might include unused code.
- Developers needing polyfills for very new or niche web standards (e.g., ES2020+ features or specific CSS Grid APIs) not covered in the included ECMAScript up to ES2017 or experimental sections.
Pros & Cons
Pros
Covers ES5 through ES2017 standards, providing consistent JavaScript behavior in older browsers, as detailed in the separate es5.js, es6.js, etc., files for incremental adoption.
Splits polyfills into files matching Web standards (e.g., html.js, dom.js), allowing developers to include only what's needed, reducing payload size based on browser requirements.
Focuses on filling practical gaps without aiming for 100% spec compliance, making it lightweight and suitable for real-world use, as stated in the README's philosophy section.
Offers minified bundles like web.js and polyfill.js for common use cases, simplifying quick integration without manual configuration.
Provides polyfills for proposed ECMAScript features and uncommon APIs (e.g., setImmediate, Geolocation), giving early access to cutting-edge functionality, though noted as unstable.
Cons
Explicitly not packaged as Node.js modules; the README states 'there's nothing to require()', limiting its use to browser-only environments and ignoring server-side needs.
The collection is curated and may miss some polyfills; it references an external guide for a more comprehensive list, indicating potential gaps for specific use cases.
Pre-bundled versions (e.g., polyfill.js) include everything, which can add unnecessary code if not carefully managed, especially for projects only needing a subset of polyfills.
Experimental polyfills are 'subject to change at any time,' as warned in the README, which could lead to breaking changes in production code relying on them.
Frequently Asked Questions
Related Projects
core-jsStandard Library
es6-promiseA polyfill for ES6-style Promises
es6-shimECMAScript 6 compatibility shims for legacy JS engines
Object.assignES2015 Object.assign() ponyfill
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