var setA = new Set([1, 9, 11]); console.log('Set A =>', [...setA]); var setB = new Set([1, 4, 8, 9, 11]); console.log('Set B =>', [...setB]); function union(setA, setB) { return new Set([...setA, ...setB]); } const unionSet = union(setA, setB); console.log(' A union B =>', ...unionSet);