var arr =[13,41,4,1,2,23,5,3,65,6,7,12,33,21,]

var res = arr.reduce(
            function (prev,curr) {
                if(!prev.includes(curr)){
                    prev.push(curr);
                }
                //不管结果如何，一定要返回数据，作为下一次的prev使用
                return prev;

            }, []
        );
        console.log(res);