利用set集合求数组的并集、交集、差集

并集

const arr1 = [11, 22, 44, 33, 55, 33, 77];
const arr2 = [66, 55, 44, 33, 88, 99, 99];
console.log("并集", [...new Set([...arr1, ...arr2])]);

交集

const cross = [...new Set(arr1)].filter(
item => arr2.indexOf(item) >= 0);
console.log("交集", cross)

差集

console.log("差集", [...new Set([...arr1, ...arr2])].filter(item => cross.indexOf(item) < 0))

补充，字符串转数组

const str = new Set('abcdefg');
const arr = [...str];
console.log(arr);