No need of using sonar.language property anymore :)
Besides this property does not admit more than one language :(
sonar.sources=src/showcase/app/
# Language
-sonar.language=js
+# My project has HTML and JavaScript. Comma separated languages do not work.
+# However since SonarQube 4.2 we do not need to declare the project's languages.
+# SonarQube detects by itself what languages is using the project to be analyzed!!
+# See: http://stackoverflow.com/a/13625963
+#sonar.language=js THIS OPTION IS NOT REQUIRED ANYMORE :)
# Encoding of sources files
sonar.sourceEncoding=UTF-8