This is honestly really neat to see! Can it run in reverse, ie: take JS code and turn it into S-expressions? If it can then this would be an interesting way to write JS using an S-expression aware editor like emacs!
It would be quite difficult in the general case to keep JavaScript formatted the same after it's been munged into S-expressions and converted back again. It would work the same, just look different. And the comments would disappear!
However, there has been some work into making a spec for a JS Concrete Syntax Tree (as opposed to Abstract Syntax Tree) which would retain whitespace, comments, and other such concrete "junk" that an AST typically abstracts out. https://github.com/estree/estree/issues/41; https://github.com/cst/cst It would be super cool to turn up at work in a JS shop armed with Emacs, and writing JavaScript at lightning speed using macros and structural editing, without anyone noticing.
It's a good idea. I'll make a note of it.