> not slowing one's work
Put back into context, your reply makes sense as these popular libraries are pretty battle tested. Having said that, it is a valid point that type hints being voluntary means they can only be relied upon with discipled developers and for code you control. Of course, the same point could be made for any code you can't control, especially if the library is written in a weakly typed language like C (or JS).
> I just don't see its absence as the crippling dealbreaker
My genuine question would be: what does dynamic typing offer over static typing? Verbosity would be my expectation, but that only really seems to apply without type inference. The other advantage often mentioned is that it's faster to iterate. Both of these don't seem particularly compelling (or even true) to me, but I'm probably biased as I've spent all of my career working with static typing, aside from a few projects with Python and JS.
> if there are languages besides JS that you feel get their type system "just right", I'd be curious as to what they are
This is use case dependent, of course. Personally I get on well with Nim's (https://nim-lang.org/) type system: https://nim-lang.org/docs/manual.html#types. It's certainly not perfect, but it lets me write code that evokes a similar 'pseudocode' feel as Python and gets out of my way, whilst being compile time bound and very strict (the C-like run time performance doesn't hurt, too). It can be written much as you'd write type hinted Python, but it's strictness is sensible.
For example, you can write `var a = 1.5; a += 1` because `1` can be implicitly converted to a float here, but `var a = 1; a += 1.5` won't compile because int and float aren't directly compatible - you'd need to type cast with something like `a += int(1.5)`, which makes it obvious something weird is happening.
Similarly `let a = 1; let b: uint = a` will not compile because `int` and `uint` aren't compatible (you'd need to use `uint(a)`). You can however write `let b: uint = 1` as the type can be implicitly converted. You can see/play with this online here: https://play.nim-lang.org/#ix=3MRD
This kind of strict typing can save a lot of head scratching issues if you're doing low level work, but it also just validates what you're doing is sensible without the cognitive overhead or syntactic noise that comes from something like Rust (Nim uses implicit lifetimes for performance and threading, rather than as a constraint).
Compared to Python, Nim won't let you silently overwrite things by redefining them, and raises a compile time error if two functions with the same name ambiguously use the same types. However, it has function overloading based on types, which helps in writing statically checked APIs that are type driven rather than name driven.
One of my favourite features is distinct types, which allow you to model different things that are all the same underlying type:
type
DataId = distinct int
KG = distinct int
Data = object
age: Natural # Natural is a positive only integer.
weight: KG
var data: seq[Data]
proc newData: DataId =
data.setLen data.len + 1
DataId(data.high) # Return the new index as our distinct type.
proc update(id: DataId, age: Natural, weight: KG) =
data[id.int] = Data(age: age, weight: weight)
let id = newData()
id.update(50, 50.KG) # Works.
50.update(50, 50.KG) # Type mismatch got int but expected DataId.
id.update(50, 50) # Type mismatch got int but expected KG.
id += 1 # Type mismatch += isn't defined for DataId.
As you can imagine, this can save a lot of easy to make accidents from happening but also enriches simple integers to serve other purposes. In the case of modelling currencies (e.g.,
https://nim-lang.org/docs/manual.html#types-distinct-type) it can prevent costly mistakes, but you can `distinct` any type. Beyond that there's structural generics, typeclasses, metaprogramming, and all that good stuff. All this to say, personally I value strict static typing, but don't like boilerplate. IMHO, typing should give you more modelling options whilst checking your work for you, without getting in your way.