Show HN: Simple 2D Physics Engine in JavaScript

I'm teaching myself some JavaScript with this project. Please feel free to make suggestions. I know I should modularize it (is that a word?) but alas, being new to JavaScript I don't yet know how to do that. I also know that ideally there should be comments in my code, which I will add. But please suggest any best practices/improvements.

You might want to check out this one

https://github.com/aguaviva/Physics