You are correct. Scala.js compiles Scala code to JS, not bytecode. A number of core Java classes have been ported to Scala.js so they can be used anyway, though

You are correct. Scala.js compiles Scala code to JS, not bytecode. A number of core Java classes have been ported to Scala.js so they can be used anyway, though. (see http://lihaoyi.github.io/hands-on-scala-js/#JavaAPIs http://lihaoyi.github.io/hands-on-scala-js/#JavaAPIs for a mostly exhaustive list so far)