QooXDoo (Score 1)

I can't really help with the strongly typed bit. But for a C++/Java guy doing GUI work I think you might like the QooXDoo library. It sort of compiles the javascript with a python script. The python compiler script will catch some mis-typing errors but certainly not all, you still have to be on your toes. However, what I really like about QooXDoo is that it frames HTML GUI development in a style that is reminiscent of Java or C++ widget libraries. The system has really allowed me to be productive at a level I would not have been able to tolerate previously.