两个数组的并集、交集、差集

    // 两个数组的并集、交集、差集
    // 不能出现重复项，得到的结果是一个新的数组
    const arr1 = [33, 22, 55, 33, 11, 33, 5];
    const arr2 = [22, 55, 77, 88, 88, 99, 99];

    // 并集
    const union = [...new Set([...arr1, ...arr2])];
    console.log(`并集 => ${union}`);

    // 交集
    const cross = [...new Set(arr1)].filter(item => {
      return arr2.includes(item)
    })
    console.log(`交集 => ${cross}`);

    // 差集
    const diff = union.filter(item => {
      return !cross.includes(item)
    })
    console.log(`差集 => ${diff}`);