Sorry to say, it's not. F# is nowhere near the wonderful type-sytem of Ocaml(although it's intentional). I would stick with js_of_ocaml for my js needs.

last time I check, did not find a way to integrate jsoo easily with existing js code. is it any tutorial on how to write a js lib using jsoo?

You have to write binding glue code. Last i saw reason also required binding code to work.

Here is a react binding for jsoo: https://github.com/jchavarri/jsoo-react .