Polyfills and shims

12-month change compares the average of the last 4 weeks of downloads with the first 4 weeks of the 52-week series. Gzip size is for the whole package, as measured by Bundlephobia. "-" means the value has not been fetched.

• symbol-observableSymbol.observable ponyfill
• node-abort-controllerAbortController for Node based on EventEmitter
• headers-polyfillA native "Headers" class polyfill.
• es6-promiseA lightweight library that provides tools for organizing asynchronous code
• urlpattern-polyfillPolyfill for the URLPattern API
• homedir-polyfillNode.js os.homedir polyfill for older versions of node.js.
• assign-symbolsAssign the enumerable es6 Symbol properties from one or more objects to the first object passed on the arguments. Can be used as a supplement to other extend, assign or merge methods as a polyfill for the Symbols part of the es6 Object.assign method.
• formdata-nodeSpec-compliant FormData implementation for Node.js
• pinkie-promiseES2015 Promise ponyfill
• markyPerformance timer based on performance.mark() and measure()
• regenerator-transformExplode async and generator functions into a state machine.
• buffer-indexof-polyfillThis is a polyfill for Buffer#indexOf introduced in NodeJS 4.0.
• listenercountbackwards compatible version of builtin events.listenercount
• es5-extECMAScript extensions and shims
• es6-symbolECMAScript 6 Symbol polyfill
• resize-observer-polyfillA polyfill for the Resize Observer API
• @react-native/js-polyfillsPolyfills for React Native.
• object.getownpropertydescriptorsES2017 spec-compliant shim for `Object.getOwnPropertyDescriptors` that works in ES5.
• extJavaScript utilities with respect to emerging standard
• os-homedirNode.js 4 `os.homedir()` ponyfill
• is-absoluteReturns true if a file path is absolute. Does not rely on the path module and can be used as a polyfill for node.js native `path.isAbolute`.
• util.promisifyPolyfill/shim for util.promisify in node versions < v8
• harmony-reflectES5 shim for ES6 (ECMAScript 6) Reflect and Proxy objects
• number-is-nanES2015 `Number.isNaN()` ponyfill
• babel-runtimebabel selfContained runtime
• is-nanES2015-compliant shim for Number.isNaN - the global isNaN returns false positives.
• code-point-atES2015 `String#codePointAt()` ponyfill
• path-dirnameNode.js path.dirname() ponyfill
• unfetchBare minimum fetch polyfill in 500 bytes
• scroll-into-view-if-neededPonyfill for upcoming Element.scrollIntoView() APIs like scrollMode: if-needed, behavior: smooth and block: center
• array-find-indexES2015 `Array#findIndex()` ponyfill
• array.prototype.reduceAn ES5 spec-compliant `Array.prototype.reduce` shim/polyfill/replacement that works as far down as ES3.
• is-finiteES2015 Number.isFinite() ponyfill
• es6-weak-mapECMAScript6 WeakMap polyfill
• fromentriesObject.fromEntries() ponyfill (in 6 lines)
• fake-indexeddbFake IndexedDB: a pure JS in-memory implementation of the IndexedDB API
• object.hasownES spec-compliant shim for Object.hasOwn
• buffer-alloc-unsafeA [ponyfill](https://ponyfill.com) for `Buffer.allocUnsafe`.
• map-or-similarA JavaScript (JS) Map or Similar object polyfill if Map is not available.
• @juggle/resize-observerPolyfills the ResizeObserver API and supports box size options from the latest spec
• string.prototype.padendES2017 spec-compliant String.prototype.padEnd shim.
• pony-causePonyfill and helpers for Error Causes
• promise-polyfillLightweight promise polyfill. A+ compliant
• iterallMinimal zero-dependency utilities for using JavaScript Iterables in all environments.
• is-functionis that thing a function? Use this module to find out
• string.prototype.codepointatA robust & optimized `String.prototype.codePointAt` polyfill, based on the ECMAScript 6 specification.
• webrtc-adapterA shim to insulate apps from WebRTC spec changes and browser prefix differences
• jsbiJSBI is a pure-JavaScript implementation of [the ECMAScript BigInt proposal](https://tc39.es/proposal-bigint/), which officially became a part of the JavaScript language in ES2020.
• @edge-runtime/ponyfillA ponyfill (doesn't overwrite the native methods) to use Edge Runtime APIs in any environment.
• react-native-url-polyfillA lightweight and trustworthy URL polyfill for React Native

• scroll-into-view-if-needed vs @juggle/resize-observer
• css-vars-ponyfill vs object-fit-images