I believe the instructions given in lesson 13 are incorrect: "Complete your program by adding the .on() event handler as described above. It should go inside your $(document).ready(), but after and outside your $('#button').click()."
....when in fact: the .on() event handler should go inside your $('#button').click() function.
Awesome, this block of code looks so fresh and clean...I think it's VERY useful that admins post the correct code here, because I believe that most students only come to the Q&A forum after they have tried without help for at least 20 minutes. And if they dont: they should ^^