jax has nice e2 = e.at[lbl].set(value)

syntax, and Ramda has

e2 = assoc(lbl, value, e)

which is curried and data-last, so you can keep that setter around for future instances of e. Usually not too bad to translate Ramda into your language of choice, and a valuable exercise. I did it with Python and it helped a TON

Once JS gets immutables, web devs will have more tools for FP, and we can look forward to that expanding the community of functional programmers a lot: (https://www.infoworld.com/article/3569118/ecma-proposal-woul...)

Python’s lack of an immutable map is annoying but there are nice pip packages for it