Simplifying array diff code using syntax sugar - coffeescript

Question

Can I simplify this array diff code, using some coffeescript syntax sugar I didn't know about?
first = [{id:1},{id:2},{id:3},{id:4},{id:5}]
second = [{id:3},{id:4},{id:5},{id:6},{id:7}]
first = first.filter (first_element) ->
second = second.filter (second_element) ->
if first_element.id == second_element.id
first_element.remove = second_element.remove = true
return !second_element.remove?
return !first_element.remove?
console.log(first.concat second) # [{id:1},{id:2},{id:6},{id:7}]

Answer 1

This one translates to exactly the same javascript:
first = [{id:1},{id:2},{id:3},{id:4},{id:5}]
second = [{id:3},{id:4},{id:5},{id:6},{id:7}]
first = first.filter (first_element) ->
second = second.filter (second_element) ->
first_element.remove = second_element.remove = yes if first_element.id is second_element.id
!second_element.remove?
!first_element.remove?
console.log(first.concat second) # [{id:1},{id:2},{id:6},{id:7}]
The explicit returns were removed, the if was put at the end of the line. yes is replaced with true and == is replaced with is.
While not shorter in lines, this one preserves the objects in the Arrays:
first = first.filter (firstElement) ->
keepFirst = yes
second = second.filter (secondElement) ->
keepFirst = (keepSecond = secondElement.id isnt firstElement.id) and keepFirst
keepSecond
keepFirst
Note that you can't use the and= operator, because it short cirquits.