I'm a huge proponent of using the same language in front and back end. My best teams had C++ front & back, or C# front and back, even Java front and back. Even though one language/platform isn't ideal for both ends, the benefit of getting everyone on the same tools, libraries, processes and way of thinking is invaluable.

So these days where most front ends are JS, it makes a lot of sense to have a JS back end too.