after.js

ScalaJS.c.example_ScalaJSExample$.prototype.main__V = (function() {
  var paragraph = ScalaJS.g["document"]["createElement"]("p");
  var l = ScalaJS.modules.scala_collection_immutable_List().apply__Lscala_collection_Seq__Lscala_collection_immutable_List(ScalaJS.modules.scala_Predef().wrapIntArray__AI__Lscala_collection_mutable_WrappedArray(ScalaJS.makeNativeArrayWrapper(ScalaJS.data.scala_Int.getArrayOf(), [1, 2, 3])));
  var l2 = ScalaJS.as.scala_collection_immutable_List(l.$$colon$plus__O__Lscala_collection_generic_CanBuildFrom__O(ScalaJS.bI(4), ScalaJS.modules.scala_collection_immutable_List().canBuildFrom__Lscala_collection_generic_CanBuildFrom()));
  paragraph["innerHTML"] = (("<strong>Here's a list"  + l2) + "</strong>");
  ScalaJS.g["document"]["getElementById"]("playground")["appendChild"](paragraph)
});
Scala

before.scala

  def main(): Unit = {
    val paragraph = g.document.createElement("p")
    val l: List[Int] = List(1,2,3)
    val l2 = l :+ 4
    paragraph.innerHTML = "<strong>Here's a list " + l2 + "</strong>"
    g.document.getElementById("playground").appendChild(paragraph)
  }