heaps VS miso

You can implement all this in Haskell (and Kmett has), but the double-layer functor presentation is beautiful in its expression of recursion and memoization through the composition of first-class modules. Yes, you could do this with typeclasses in Haskell, but typeclasses but I think there's just an element of elegance to first-class modules that can't be found with typeclasses. (Not the mention Haskell's horridly bare-bones module system.)

Patching jsaddle by applying this commit made JSaddle usable in Firefox for me, but it has the downside that preventDefault/stopPropagation no longer work (see this issue for more info).

Miso does support jsaddle, docs mention this under the "Live reload with jsaddle" section, although it could be more prominent.

For those interested in DOM-related benchmarks using GHCJS. Miso has some benchmarks here: https://krausest.github.io/js-framework-benchmark/current.html (Ctrl+F `miso`)

ghcjs is the way to go for you, and soon it might be asterius. i do not know how hard it is to set ghcjs up without a framework. but frameworks like obelisk (based on reflex-dom), shpadoinkle, and miso automate that for. i personally like obelisk for its functional reactive programming but it can get awkward and get in your way. so if gui programming is just a means to the end of this one small application and you are not really interested in it nor functional reactive programming, shpadoinkle or miso might suit you better. miso implements the elm architecture (also "TEA", "functional model view controller") and shpadoinkle implements something directly equivalent to the elm architecture. but shpadoinkle achieves more composable widgets by minimalizing the elm architecture. so i recommend shpadoinkle for its better concept although miso is more mature.