Why would you need anything other than Javascript? It's a modern language made for agile development of user experiences. It is dynamic-oriented with prototypical polymorphism and is the basis for the open web. Thanks to technologies like V8 and asm.js, binary-blob VMs are a thing of the past and native executables can be relegated to drivers and such. If you need any other language, you can just compile it to Javascript, but really, why bother!