Simple and complete DOM testing utilities that encourage good testing practices.

An ES2019 spec-compliant `Array.prototype.flat` shim/polyfill/replacement that works as far down as ES3.

Gets the description of a Symbol. Handles `Symbol()` vs `Symbol('')` properly when possible.

Is this value a JS regex? Works cross-realm/iframe, and despite ES6 @@toStringTag

ES spec-like internal slots

Custom jest matchers to test the state of the DOM

This plugin adds `TypeScript` support to `eslint-plugin-import`

Is this value a JS Number object? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

An ESnext spec-compliant `Array.prototype.findLastIndex` shim/polyfill/replacement that works as far down as ES3.

Is this value a JS Boolean? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

ES Math-related intrinsics and helpers, robustly cached.

Determine if the JS environment has BigInt support.

Unbox a boxed JS primitive value.

ECMAScript spec-compliant polyfill/shim for `globalThis`

Does this JS environment support the `name` property on functions?

ECMAScript “ToPrimitive” algorithm. Provides ES5 and ES2015 versions.

Is this value a JS Date object? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Which kind of Collection (Map, Set, WeakMap, WeakSet) is this JavaScript value? Works cross-realm, without `instanceof`, and despite Symbol.toStringTag.

Is this value an ES BigInt?

Property based testing framework for JavaScript (like QuickCheck)