Also, as someone who both works on open source reactive stuff (like MobX) and literally works on a spreadsheet app (Excel) I can say what we do is entirely different from what these systems do because of different constraints and both are reactive.
In a gist: MobX just keeps the whole dependency graph of what data needs to update when what computed runs. Excel can't do that because it has to be able to work on large files with impartial data.
