Err... C & C++ are the primary languages used in typical safety-critical systems. I've used it. JS... of course no one uses that mainly because the abstraction

Err... C & C++ are the primary languages used in typical safety-critical systems. I've used it. JS... of course no one uses that mainly because the abstraction level is too high, the number of layers of non-safety-critical code massively outweighs the application code. The critical thing about safety-critical code isn't really about the code... its the whole development process. Implementation is just one small part of that process.