const a = new Set([1, 2, 3, 4, 4, 4])
const b = new Set([3, 4, 5, 6])

const intersect = (set1, set2) => [...set1].filter(num => set2.has(num))
const differ = (set1, set2) => [...set1].filter(num => !set2.has(num))
const joinSet = (set1, set2) => [...set1, ...set2]

const myIntersectedSet = new Set(intersect(a, b))
console.log('myIntersectedSet', myIntersectedSet)

const myDifferenceSet = new Set(differ(a, b))
console.log('myDifferenceSet', myDifferenceSet)

const myJoinedSet = new Set(joinSet(a, b))
console.log('myJoinedSet', myJoinedSet)