js set to achieve intersection, union, and difference

let a=new Set([1,2,3])
let b=new Set([4,3,2])

// 并集
let union=new Set([...a,...b])
// 交集
let intersect=new Set([...a].filter(x=>b.has(x)))
// 差集
let difference=new Set([...a].filter(x=>!b.has(x)))

effect:

Source: http://es6.ruanyifeng.com/#docs/set-map