js倒計時插件

/**
 * 倒計時
 * $("#end_time").val() 的格式是2019-04-15 15:00:00
 * $("#ms_time").val() 的格式是1555485125000
 * 額，這個有點不規範，不過代碼還是好代碼。後面會修改整合的！
 */

function countDown(){

    if($("#end_time").val()!=null&&$("#end_time").val()!=''){

        var day_elem = $(".js-day");

        var hour_elem = $(".js-hour");

        var minute_elem = $(".js-min");

        var second_elem = $(".js-sec");

        var end_time = new Date($("#end_time").val().replace(/-/g,'/')).getTime();//月份是實際月份-1

        sys_second = (end_time-$("#ms_time").val())/1000;

        if(sys_second>1){

            sys_second -= 1;

            var day = Math.floor((sys_second / 3600) / 24);

            var hour = Math.floor((sys_second / 3600) % 24);

            var minute = Math.floor((sys_second / 60) % 60);

            var second = Math.floor(sys_second % 60);

            day_elem && $(day_elem).text(day);//計算天

            $(hour_elem).text(hour<10?"0"+hour:hour);//計算小時

            $(minute_elem).text(minute<10?"0"+minute:minute);//計算分鐘

            $(second_elem).text(second<10?"0"+second:second);//計算秒

        }

        var timer = setInterval(function(){

            if (sys_second > 1) {

                sys_second -= 1;

                var day = Math.floor((sys_second / 3600) / 24);

                var hour = Math.floor((sys_second / 3600) % 24);

                var minute = Math.floor((sys_second / 60) % 60);

                var second = Math.floor(sys_second % 60);

                day_elem && $(day_elem).text(day);//計算天

                $(hour_elem).text(hour<10?"0"+hour:hour);//計算小時

                $(minute_elem).text(minute<10?"0"+minute:minute);//計算分鐘

                $(second_elem).text(second<10?"0"+second:second);//計算秒

            } else {

                clearInterval(timer);

            }

        }, 1000);

    }

}