活动倒计时，可同步服务器时间，倒计时格式随意设置

/*
#活动倒计时，可同步服务器时间
startTime:起始时间
endTime:结束时间
format_str：字符模板
speed：倒计时执行速度
callback:倒计时结束回调
$('.xxx').countDown_str({
  startTime:'2018-09-28 11:09:00',
  endTime: '2018-09-29 11:09:00',
  format_str: '<span class="dd">{d}</span><span class="hh">{h}</span><span class="mm">{m}</span><span class="ss">{s}</span><span class="hs">{hs}</span>'
});
//字符模板详细说明
{d}天数
{h}小时
{m}分钟
{s}秒
{hs}毫秒
*/

 

主体代码：

$.fn.countDown_str = function (options) {
    var defaults = {
        startTime: '2018-09-28 11:09:00',
        endTime: '2018-09-29 11:09:00',
        speed: 1000,
        format_str: '<span class="dd">{d}</span><span class="hh">{h}</span><span class="mm">{m}</span><span class="ss">{s}</span><span class="hs">{hs}</span>',
        callback: function () {
 
        }
    }
    var opt = $.extend({}, defaults, options);
 
    return this.each(function () {
        var that = this,
            timer = '';
 
        function init() {
            var nowTimeStamp = new Date().getTime();//服务器的开始时间
            var nowTimeStamp_server = new Date(opt.startTime).getTime();
            this.totalTime = nowTimeStamp - nowTimeStamp_server;//服务器与本地时间差
        }
 
        init.prototype.format = function (str, args) {
            var result = str;
            if (arguments.length > 0) {
                if (arguments.length == 2 && typeof (args) == "object") {
                    for (var key in args) {
                        if (args[key] != undefined) {
                            var reg = new RegExp("({" + key + "})", "g");
                            result = result.replace(reg, args[key]);
                        }
                    }
                }
            }
            return result;
        };
 
        init.prototype.outputTime = function () {
            var date = this.date,
                endTime = opt.endTime,
                format_str = opt.format_str;
            var nowTimeStamp = new Date().getTime();
            var endTimeStamp = new Date(endTime).getTime();
            var surplusTime = endTimeStamp - nowTimeStamp + this.totalTime;
            var d = parseInt((surplusTime / (1000 * 60 * 60 * 24)));
            var _d = d < 10 ? '0' + d : d;
            var h = parseInt((surplusTime % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60)); //时
            var _h = h < 10 ? '0' + h : h;
            var m = parseInt((surplusTime % (1000 * 60 * 60)) / (1000 * 60)); //分
            var _m = m < 10 ? '0' + m : m;
            var s = ((surplusTime % (1000 * 60)) / 1000).toString(); //秒
            var s1 = s.toString().split('.')[0]; //秒
            var _s1 = s1 < 10 ? '0' + s1 : s1;
            var _s3 = (s - s1).toFixed(3).toString().substring(2);
            if (surplusTime > 0) {
                format_str = init.format(format_str, {
                    d: _d,
                    h: _h,
                    m: _m,
                    s: _s1,
                    hs: _s3
                });
            } else {
                format_str = init.format(format_str, {
                    d: '00',
                    h: '00',
                    m: '00',
                    s: '00',
                    hs: '000'
                });
                clearInterval(timer);
                //定时器结束灰调
                if (typeof opt.callback == 'function') {
                    opt.callback();
                }
            }
            $(that).html(format_str);
 
        }
        var init = new init();
        init.outputTime();
        timer = setInterval(function () {
            init.outputTime();
        }, opt.speed);
 
    });
}