Return.md

== Javascript

~ » node
> console.log([1,2,3].map(function(n){n*2}))
[ undefined, undefined, undefined ]
> console.log([1,2,3].map(function(n){return n*2}))
[ 2, 4, 6 ]

== Ruby

~ » irb
>> [1,2,3].map{|n| n*2}
=> [2, 4, 6]