I've never dealt much with transpiling to JS, but I would guess that it's a lot easier to do it from the AST or some other higher-level intermediate representat

I've never dealt much with transpiling to JS, but I would guess that it's a lot easier to do it from the AST or some other higher-level intermediate representation than it is from CIL instructions. That way you don't have to fuss with programmatically figuring out what stack manipulation instructions are trying to accomplish or any other target-specific noise like that.