We don't need to use those brackets because the "concat" method accepts different types, not only array. Also I think we should use a for loop and compare the values in it instead of filtering values twice, but maybe that would be more understandable so I didn't change it.
We don't need to use those brackets because the "concat" method accepts different types, not only array. Also I think we should use a for loop and compare the values in it instead of filtering values twice, but maybe that would be more understandable so I didn't change it.