> The flatMap() method first maps each element using a mapping function, then flattens the result into a new array. It is identical to a map() followed by a flat() of depth 1, but flatMap() is often quite useful, as merging both into one method is slightly more efficient.
Used with flatMap, it's a terribly good way of doing something to everything over an arbitrary object and all it's deep values. I do something like this every month or so.
It's one of those tricks you use a lot once you've seen the problems it's applicable to.
