Sure, no arguments there. It does save time in JavaScript and a large part of that is because the language has been designed around mutability. Part of that tr

Sure, no arguments there. It does save time in JavaScript and a large part of that is because the language has been designed around mutability. Part of that trade-off is that JavaScript can't make the same guarantees about what happens when you pass an object into a function. It's harder to be confident that a given program is correct. Immutability is just a part of the "simple made easy"[1] ethos of Clojure and I think most Clojure programmers will argue that taking the time to understand that philosophy _is_ worth the investment. [1] https://www.youtube.com/watch?v=rI8tNMsozo0 https://www.youtube.com/watch?v=rI8tNMsozo0