Since JavaScript isn't really everyone's cup of tea, or coffee. Various languages that compile to JavaScript have emerged. Usually these languages provide some constructs not found in the core language. You may gain better type checking or some syntactical sugar.
altJS lists many of these languages. If you have time, go and check out a few. Personal recommendations: CoffeeScript, Dart, TypeScript, Elm.
Some daredevils use emscripten to run arbitrary code in JavaScript. It is a system built on top of LLVM and makes many perhaps a bit crazy things possible. You can for instance play Dune 2 or Transport Tycoon Deluxe in your browser. How retro is that?