You have to follow a set of rules - your example would not be allowed. One of the nice things about ClojureScript is that the compiler will output compatible c

You have to follow a set of rules - your example would not be allowed. One of the nice things about ClojureScript is that the compiler will output compatible code, so you don't even really have to think about it (except when doing JS interop). If you write valid ClojureScript, it Just Works.