Completely unrelated.<p>- Immer (C++) appears to be roughly equivalent to Immutable.js ( <a href="https://immutable-js.com/" rel="nofollow">https://immutable-js.com/</a> ): a set of specialized data structures<p>- Immer (JS), on the other hand, uses JS Proxies to wrap plain values, traps attempted mutations, and then replays them to return a safely immutable updated final result<p>As far as I know, Michel Weststrate came up with the name independently (although I can't 100% confirm that).<p>(source: I didn't create Immer (JS), but I started using it in Redux Toolkit in 2018, am quoted in the docs about how much I love it, spent the last couple months doing performance optimization work that got shipped in Immer 11.x, and just put up some more bugfix PRs today. I'm a secondary maintainer at this point.)