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

Generic configuration validation tool that helps you with warnings, errors and deprecation messages as well as showing users examples of correct configuration.

Runtime type checking for React props and similar objects.

Utilities for ESLint plugins.

Babel helper functions for inserting module loads

<sup> tag for markdown-it markdown parser.

A stupidly simple key/value storage using files to persist some data

Safer Node.js Buffer API

javascript standard data structure library which benchmark against C++ STL

Import a module while bypassing the cache

Wrap class field initializers with IIFE to workaround https://webkit.org/b/236843

tar-stream is a streaming tar parser and generator and nothing else. It is streams2 and operates purely using streams which means you can easily extract/parse tarballs without ever hitting the file system.

A basic but performant promise implementation

Traverse an ESTree-compliant AST

Regular expression for matching ANSI escape codes

Convert CommonJS modules to ES2015

HTTP proxying for the masses

[](https://www.npmjs.com/package/ip)

Explode async and generator functions into a state machine.

Parsing the JavaScript's RegExp in JavaScript.

A tidy ISO 8601 date formatter and parser

Brand checking of React Elements.

A robust Punycode converter that fully complies to RFC 3492 and RFC 5891, and works on nearly all JavaScript platforms.

Babel transformer for React Native applications.