SharedMap is a zero‑dependency JavaScript library that provides a high‑performance, thread‑safe hash map built on top of **SharedArrayBuffer** and Atomics. It implements a coalesced‑chaining hashmap with fine‑grained locking, deadlock recovery, static memory allocation and auto‑defragmentation, making it suitable for multi‑threaded Node.js (and compatible browser) applications that need fast shared key/value storage of numbers and strings.