[brudgers]

Scala.js, Clojure.js etc. treat JavaScript as assembly language and the browser as a target architecture. It's not about porting applications. It is about accessing the same data structures and abstractions on both ends of the wire when writing code.

For languages like Scala this means things as obvious as keeping class based inheritance with traits when writing client code for the browser. Those classes can share the same hierarchy with the server side.

This means that the decisions about where to execute a feature becomes less likely to be driven by differences between client and server language features. The effort can be put into determining which execution environment better solves the problem.