[droppedonjapan_]

You might want to consider including something about how passing objects between functions can be by reference or value for object oriented Javascript programming.

[suyash]

JavaScript only supports pass by value, @ author: Nice quiz, I failed the last one, it would be nice to add more quizes and test users knowledge of function scoping, just like the commenter said, since functions can be passed around like objects, function scoping is another tricky one to master for beginners.

[japrescott]

not true. boolean, strings, numbers (int, float) are passed by value, while Objects, Arrays and Functions are passed by reference!