+1. If you want threads, build a node c++ addon that manages your threads/high performance work (and try not to pass too much back and forth with your Javascript, because of the performance overhead of marshaling described above). Which means you are just writing a lot of C++, and your javascript simply becomes a convenient interface to start/stop the processing and script actions on values emitted from your c++ addon.

Or, like everyone else recommends: use processes and ipc (e.g., the cluster module).