JS

    <script>
        let arr=[1,2,3,4,5,4,3,2,1];
        //1.数组去重
        let result0=[...new Set(arr)];
        console.log(`数组去重${result0}`);

        //2.交集
        let arr2=[4,5,6,5,6];
        let result=[...new Set(arr)].filter(item=>{
            let s2=new Set(arr2);//4 5 6
            if(s2.has(item)){
                return true;
            }else{
                return false;
            }

        })
        console.log(`交集${result}`);
        let result2=[...new Set(arr)].filter(item=>new Set(arr2).has(item));
        console.log(`交集${result2}`);

        //3.并集
        let union=[...new Set([...arr,...arr2])];
        console.log(`并集${union}`);

        //4.差集
        let diff=[...new Set(arr)].filter(item=> !(new Set(arr2).has(item)));
 
        console.log(`并集${diff}`);
    </script>