Material UI is an open-source React component library that implements Google's Material Design. It's comprehensive and can be used in production out of the box.
Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with different data types like numbers, big numbers, complex numbers, fractions, units, and matrices.
Internationalize React apps. This library provides React components and an API to format dates, numbers, and strings, including pluralization and handling translations.
The fastest in-browser CSV (or delimited text) parser for React. It is full of useful features such as CSVReader, CSVDownloader, readString, jsonToCSV, readRemoteFile, ... etc.