My favorite bit of wat.js is this:

    [1,2,3] + [4,5,6] // => "1,2,34,5,6"

I mean, it makes some degree of logical sense (toString -> concat) but there is no reason that would ever be the intended behavior.

As for that expression, meh. You can write intentionally obtuse code in any language. The problem with JS is the behavior that is different from what you'd expect.