[marshray]

If you've ever gone through a phase (or a graduate degree!) of thinking deeply about programming language design, you might, as I do, find Javascript's expression evaluation behavior to be just about the funniest thing around.

[jrockway]

I have but I don't. Javascript was designed to reduce programmer-visible errors at the cost of making it nearly impossible to write a correct program. At that goal, it succeeds, and [] + {} being NaN makes perfect sense under those constraints.