These are the JS quizzes that I have up on JSFiddle.
The answers are hidden behind a toggle.
Browsable list of quizzes is here:
http://netlumination.com/blog/javascript-quizzes
My public fiddles are here:
http://jsfiddle.net/user/pajtai/fiddles/
git clone https://github.com/pajtai/JavascriptQuizzes.git
cd JavascriptQuizzes
( sleep 1 && open http://localhost:8000 ) &; python -m SimpleHTTPServer