ES6之set集合

 let arr = [1, 2, 3, 4, 5, 4, 3, 2, 1];
        //数组去重
        let result = [...new Set(arr)];
        console.log(result);
        //交集
        let arr2 = [4, 5, 5, 6, 6];
        let result = [...new Set(arr)].filter(item => {
                let s2 = new Set(arr2);
                if (s2.has(item)) {
                    return true;
                } else {
                    return false;
                }
            })
            //并集
        let union = [...new Set([...arr, ...arr2])];
        console.log(union);

        // 差集 交集取反

        let diff = [...new Set(arr).filter(item => {
            !(new Set(arr2).has(item));
        })]
        console.log(diff);