js--數組合並並且去重

//二:兩個數組合並並且去重
        let arr1 = [1, 1, 2, 3, 6, 9, 5, 5, 4];
        let arr2 = [1, 2, 5, 4, 9, 7, 7, 8, 8];
        //數組組合
        let arr12=[...arr1,...arr2];//arr1.push(...arr2);
        let delsame=[];
        let sames=[];
        let ss=[];
        for(let i=0;i<arr12.length;i++){                
            if(delsame.indexOf(arr12[i])==-1){
                delsame.push(arr12[i])
            }else{
                //這里是拿出相同的元素
                sames.push(arr12[i])
                ss=[...new Set(sames)]
            }
        }
        console.log(delsame,sames,ss)