If you do it please consider porting Crisp Game Lib, the framework used to create this game, which will net you hundreds of new C64 games in one go.

Can a C64 efficiently run JS?

Absolutely not. It can do a lot of things but any interpreted language is going to run at a snail's pace, especially not one designed specifically for the C64.

Each game really needs to be written in isolation in assembly to work round the limitations, e.g. some might need a sprite multiplexor, some might not.