On: Learn from Haskell - Functional, Reusable JavaScri...

[eru]

In Haskell there are some helper functions for these:

    longestLastname :: [Person] -> Person
    longestLastname names = maximumBy (comparing (length . lastname)) names

In general, you can do map something like

    extractProperty list = map (\x -> (f x, x)) list

Then work on the first element of the tuple (comparing for sorting etc), and at the end return the original object by extracting the second element of the tuple.