Dear madam or sir,
This bid is just per se because I don't know the quantity of the code that needs to be documented. If you could provide that kind of information we could make a deal for sure.
I'm fluent in JavaScript and I'm using Node.js actively, and using UML for last 3 to 4 years on my faculty and within cooperation with others companies and developers. UML is my choice of presenting IS to others.
If you have questions of any kind, feel free to send me a message.
Kind regards,
Matej Basic