I *believe* that by "close over anything" he is referring to the fact that you do not need a closure (which would allow variables in your scope to be available inside this function). As it is now every time `addUnsavedRecords` is called you would be creating a new function. I believe that this *might* be a performance issue.  You could make `notDuplicated` a function up out of `addUnsavedRecords` with likely the same result as the current code, but without generating a new function very time it is called.