[iLemming]

Alright, I admit, I have not worked on teams where immutable.js was used a lot, so I don't have any insight specifically on its impact on performance.

Still personally wouldn't call immutability a "trade-off", even in js context - for majority of kinds of apps, it's still a big win - I've seen that many times with Clojurescript which doesn't have native runtime - it eventually emits javascript. I love Clojure, but I honestly refuse to believe that it invariably emits higher performing js code compared to vanilla js with immutablejs on top.

For some kind of apps, yes, for sure, the performance is an ultimate priority. In my mind, that's a similar "trade-off" as using C or even assembly, because of required performance. It's undeniably important, yet these situations represent only a small fraction of overall use cases.

But sure, I agree with everything you say - Immutability is great in general, but not for every given case.