js倒计时代码实现

/** * *返回剩余时间 {} */function getTimeInfo(startTime, currentTime) {    var total = startTime.getTime() - currentTime.getTime();    return {        day: Math.floor(total/1000/60/60/24),  //天        hour: Math.floor(total/1000/60/60%24), //时        minute:  Math.floor(total/1000/60%60),  //分        second:  Math.floor(total/1000%60)  //秒    }}var firstLoadTime = true;//动态倒计时处理// startTime  开始时间 *// ajaxUrl  $ ajaxUrl 存在时执行  不存在时或ajax出错时默认以本地时间为准// attr  keyfunction executeShow(startTime, ajaxUrl, attr, log) {    var currentTime = new Date();    if (!firstLoadTime) {   //非首次获取时间        if(window.currentTime != null) {            currentTime = new Date(window.currentTime.getTime() + 1000);        }    } else {        try {            if (ajaxUrl != null && ajaxUrl.trim() != "") {  //通过ajax获取                var ajaxtime = $.ajax({                    url: ajaxUrl,                    async: false,                    dataType: "json",                    timeout: 1500,                    success: function(data) {                        try {                            if (!attr) {                                attr = "date";                            }                            var date = data[attr];  //获取输出的服务器时间                            date = date.replace(/-/g, "/");                            currentTime = new Date(date);                            if (log && console) {                                console.log("通过jquery初始化服务端时间成功");                            }                        } catch (e) {                            currentTime = new Date();                        }                    },                    complete: function(XMLHttpRequest, status) { //请求完成后最终执行参数                        if (status == 'timeout') {  //超时                            ajaxtime.abort(); //取消请求                            currentTime = new Date();                        } else if (status == 'error') {                            currentTime = new Date();                        }                    }                    });            }        } catch(e) {            currentTime = new Date();        }        firstLoadTime = false;    }    window.currentTime = currentTime;    setShowView(getTimeInfo(startTime, currentTime));   //设置页面显示的内容    setTimeout(function() {        executeShow(startTime, ajaxUrl, attr, log);    }, 1000);}//设置网页显示内容的函数,timeInfo为剩余时间jsonfunction setShowView(timeInfo) {    console.log(timeInfo);}window.onload = function() {    var startTime = new Date("2017/11/11 00:00:00");  //设置活动开始的时间    executeShow(startTime);}