Let's say you'd like to write front-end code in a language that hides as much of the problems with JS as possible, preferably one that comes with a standard library, has elegant (or at least ergonomic) JS to <lang> interop and bridging, simplifies async code, and has a simple, integrated toolchain for targeting JS (all these amongst other things), what would you suggest? Basically what's the best language to write Javascript in : )

Dart? Elm? Clojurescript? Objective-J?