ES6数组实现并集、交集、差集

let set1  = new Set(['a','b','c','d','e','f']);
let set2  = new Set(['d','e','f','g','h','i']);

//并集
let union = [...new Set([...set1,...set2])];
//[a,b,c,d,e,f,g,h,i]
//交集
let intersect = [...new Set([...set1].filter(x => set2.has(x)))];
//[d,e,f]
//差集
let dfrcset = [...new Set([...set1].filter(x => !set2.has(x)))];
//[a,b,c]