I should add to lihaoyi's reply that in addition to the target environment's libraries, many Scala libraries cross-compile for Scala JVM, Scala.js, and (to a le

I should add to lihaoyi's reply that in addition to the target environment's libraries, many Scala libraries cross-compile for Scala JVM, Scala.js, and (to a lesser extent due to its relative novelty) Scala Native. For example I am now cross-compiling JVM/JS a fairly large project which uses, directly or indirectly, Circe, Cats, ScalaTest, Enumeratum, Shapeless, and Parboiled2, and all of that works flawlessly.