3011b–Showing error message with addClass/removeClass

Background

Starting point:

http://codepen.io/pen?template=bNxGPM

1. Please implement the logic with addClass and removeClass.
2. Please add more input types, such as checkbox, textarea, emails. And show errors when any inputs are empty.
3. Please remove all error states when user changes any value of the inputs. (When user is trying to fix the error)