obfusticated javascript?

alert([">"].map(function(t,j){return t +(Array.prototype.slice.call({length:(new Date).getFullYear()}).concat("javascript").filter(function(e,i){ j = e ? i : j; return e; }).map(function(e) { return j + "\n" + t + e; }).join())}).join());

I sort of know what this is doing but, at the same time, I don't know what's it's trying to doing.

Array.prototype.slice.call({...}) is creating an Array with length equal to the returned year from a JSON object whose only property is length.  With the next statements, it adds "javascript" as the new last element of the Array. I'd hazard to say that filter() just changes the value of j; it will probably be "javascript" when done.  I don't know enough about map to be confident in my guesses beyond that point.