I was using node.js for a while and having to deal with the same bugs over and over again. Usually the bug would be passing the wrong type or mistyping a name. I started using Typescript and things got a lot better. Scala.js is great and all, and probably a good choice if you're using Scala on the backend, but Typescript works a bit better because the Javascript it generates is pretty close to the original. If you search the HN archives, people seem pretty happy with it.