let arr1 = [1, 2, 3, 4, 5, 4, 3, 2, 1]
    let arr2 = [4, 5, 6, 6, 5]
    //數(shù)組去重
    let result = [...new Set(arr1)]
    console.log(result)
    //交集
    let result1 = [...new Set(arr1)].filter(item => new Set(arr2).has(item))
    console.log(result1)
    //并集
    let result2 = [...new Set([...arr1, ...arr2])]
    console.log(result2)
    //差集
    let result3 = [...new Set(arr1)].filter(item => !(new Set(arr2).has(item)))
    console.log(result3)