intersection of two objects in javascript

1var firstObject = {
2  x: 0,
3  y: 1,
4  z: 2,
5
6  a: 10,
7  b: 20,
8  e: 30
9}
10
11var secondObject = {
12  x: 0,
13  y: 1,
14  z: 2,
15
16  a: 10,
17  c: 20,
18  d: 30
19}
20
21function getIntKeys(obj1, obj2){
22
23    var k1 = Object.keys(obj1);
24    return k1.filter(function(x){
25        return obj2[x] !== undefined;
26    });
27  
28}
29
30alert(getIntKeys(firstObject, secondObject));

1// Generic helper function that can be used for the three operations:        
2const operation = (list1, list2, isUnion = false) =>
3    list1.filter(
4        (set => a => isUnion === set.has(a.userId))(new Set(list2.map(b => b.userId)))
5    );
6
7// Following functions are to be used:
8const inBoth = (list1, list2) => operation(list1, list2, true),
9      inFirstOnly = operation,
10      inSecondOnly = (list1, list2) => inFirstOnly(list2, list1);
11
12// Sample data
13const list1 = [
14    { userId: 1234, userName: 'XYZ'  }, 
15    { userId: 1235, userName: 'ABC'  }, 
16    { userId: 1236, userName: 'IJKL' },
17    { userId: 1237, userName: 'WXYZ' }, 
18    { userId: 1238, userName: 'LMNO' }
19];
20const list2 = [
21    { userId: 1235, userName: 'ABC'  },  
22    { userId: 1236, userName: 'IJKL' },
23    { userId: 1252, userName: 'AAAA' }
24];
25  
26console.log('inBoth:', inBoth(list1, list2)); 
27console.log('inFirstOnly:', inFirstOnly(list1, list2)); 
28console.log('inSecondOnly:', inSecondOnly(list1, list2));