ES6—39：set数据结构

// 1. 数组去重
const arr = [1,2,3,4,5,5,6,8,9,9,9,9];
const result = [...new Set(arr)];
console.log(result);
// 2. 交集
const arr2 = [1,2,5,8,6];
const result2 = [...new Set(arr)].filter(item => {
    if (arr2.includes(item)) {
        return true;
    }
});
console.log(result2);
// 3. 求并集
const merge = [...new Set([...new Set(arr),...new Set(arr2)])];
console.log(merge);
// 4. arr 对 arr2 求差集  所谓的差集就是我有你没有
const sub = [...new Set(arr)].filter(item => {
    const arr2s = [...new Set(arr2)];
    if (arr2s.includes(item) === false) {
        return true;
    };
});
console.log(sub);