JS 实现时间跳动

        function currentDate(){
            var da = new Date();
            var year = da.getFullYear();
            var month = da.getMonth();
            var day = da.getDate();

            var hours = da.getHours();
            var minutes = da.getMinutes();
            var seconds = da.getSeconds();
            if(month<10){
                month = "0" + month;
            }
            if(day<10){
                day = "0" + day;
            }
            if(hours<10){
                hours = "0" + hours;
            }
            if(minutes<10){
                minutes = "0" + minutes;
            }
            if(seconds<10){
                seconds = "0" + seconds;
            }
            var datetime = year + "-" + month + "-" + day + " " + hours + ":" + minutes + ":" + seconds;
            document.getElementById("time1").innerText = datetime;
        }
        setInterval(currentDate,500);