How to add only new data?

Question

JavaScript

Good day.
It is necessary to display the data received by the link in json format with a certain interval.
Suppose the first request received data with id 1,2,3,4,5
The second - 3,4,5,6,7
How to add only 6 and 7 in the most kosher way without unnecessary garbage?
Thank you in advance

Answer 1

Solution: work with sets.
Subtract the first from the second set of id-nis. This is how the set of numbers in the second set is found, which are absent in the intersection of two sets.
I won’t give an example in JavaScript, but in Ruby it’s simple:

require 'set'
Set.new([3,4,5,6,7]) - Set.new([1,2,3,4,5])
 => #<Set: {6, 7}>