;; clj
$ clj
Clojure 1.10.0
user=> (#(inc %) 1 2)
Execution error (ArityException) at user/eval3 (REPL:1).
Wrong number of args (2) passed to: user/eval3/fn--4
;; cljs 
$ clj -m cljs.main -c perc.core -re node -r
ClojureScript 1.10.520
cljs.user=> 
cljs.user=> (#(inc %) 1 2)
2

Sorta aligns with javascripts more permissive arity handling, but could lead to less portable code

In ClojureScript, arity warnings are generated at analysis time. Arguably the analyzer could catch the example above, but it doesn't.

Arity errors are also generated at runtime for multi-arity fns.