Difference and intersection of two arrays containing objects

Question

I have two arrays list1 and list2 which have objects with some properties; userId is the Id or unique property:

list1          


        

Answer 1

Just use filter and some array methods of JS and you can do that.

let arr1 = list1.filter(e => {
   return !list2.some(item => item.userId === e.userId);
});

This will return the items that are present in list1 but not in list2. If you are looking for the common items in both lists. Just do this.

let arr1 = list1.filter(e => {
   return list2.some(item => item.userId === e.userId); // take the ! out and you're done
});