AES-JS is a pure JavaScript implementation of the AES block cipher and common modes of operation (CBC, CFB, CTR, ECB, OFB) for Node.js and web browsers. It supports 128-, 192-, and 256-bit keys, works with Typed Arrays for performance, and includes utilities for encoding/decoding binary data as hex or UTF-8. The library is designed for developers needing encryption in JavaScript without external dependencies.