function countdown(that) {
 var second = that.data.second
 if (second == 0) {
 // console.log("Time Out...");
 that.setData({
 second: "Time Out..."
 });
 return ;
 }
 var time = setTimeout(function(){
 that.setData({
 second: second - 1
 });
 countdown(that);
 }
 ,1000)
}
 
Page({
 data: {
 second: 3
 },
 onLoad: function() {
 countdown(this);
 }
});

/* 秒级倒计时 */
function countdown(that) {
 var second = that.data.second
 if (second == 0) {
 that.setData({
 second: "Time out!",
 micro_second: "micro_second too."
 });
 clearTimeout(micro_timer);
 return ;
 }
 var timer = setTimeout(function(){
 that.setData({
 second: second - 1
 });
 countdown(that);
 }
 ,1000)
}
 
/* 毫秒级倒计时 */
// 初始毫秒数，同时用作归零
var micro_second_init = 100;
// 当前毫秒数
var micro_second_current = micro_second_init;
// 毫秒计时器
var micro_timer;
 
function countdown4micro(that) {
 if (micro_second_current <= 0) {
 micro_second_current = micro_second_init;
 }
 micro_timer = setTimeout(function(){
 that.setData({
 micro_second: micro_second_current - 1
 });
 micro_second_current--;
 countdown4micro(that);
 }
 ,10)
}
 
Page({
 data: {
 second: 2,
 micro_second: micro_second_init
 },
 onLoad: function() {
 countdown(this);
 countdown4micro(this);
 }
});

<text style="display: block;">second: {{second}}s</text>
 
<text>{{micro_second}}</text>

function dateformat(second) {
 var dateStr = "";
 var hr = Math.floor(second / 3600);
 var min = Math.floor((second - hr * 3600) / 60);
 var sec = (second - hr * 3600 - min * 60);// equal to => var sec = second % 60;
 dateStr = hr + ":" + min + ":" + sec;
 return dateStr;
}
//目前有2个时钟，影响性能，合并下去掉countdown，于是countdown4micro变成以下的样子：
 
function countdown4micro(that) {
 
 var loop_second = Math.floor(loop_index / 100);
 // 得知经历了1s
 if (cost_micro_second != loop_second) {
 // 赋予新值
 cost_micro_second = loop_second;
 // 总秒数减1
 total_second--;
 
 }
 // 每隔一秒，显示值减1; 渲染倒计时时钟
 that.setData({
 clock:dateformat(total_second - 1)
 });
 
 if (total_second == 0) {
 that.setData({
 // micro_second: "",
 clock:"时间到"
 });
 clearTimeout(micro_timer);
 return ;
 } 
 
 if (micro_second_current <= 0) {
 micro_second_current = micro_second_init;
 }
 micro_timer = setTimeout(function(){
 that.setData({
 micro_second: micro_second_current - 1
 });
 micro_second_current--;
 // 放在最后++，不然时钟停止时还有10毫秒剩余
 loop_index ++;
 countdown4micro(that);
 }
 ,10)
}

/** 
 * 需要一个目标日期，初始化时，先得出到当前时间还有剩余多少秒
 * 1.将秒数换成格式化输出为XX天XX小时XX分钟XX秒 XX
 * 2.提供一个时钟，每10ms运行一次，渲染时钟，再总ms数自减10
 * 3.剩余的秒次为零时，return，给出tips提示说，已经截止
 */
 
// 定义一个总毫秒数，以一分钟为例。TODO，传入一个时间点，转换成总毫秒数
var total_micro_second = 2 * 1000;
 
/* 毫秒级倒计时 */
function countdown(that) {
 // 渲染倒计时时钟
 that.setData({
 clock:dateformat(total_micro_second)
 });
 
 if (total_micro_second <= 0) {
 that.setData({
 clock:"已经截止"
 });
 // timeout则跳出递归
 return ;
 } 
 setTimeout(function(){
 // 放在最后--
 total_micro_second -= 10;
 countdown(that);
 }
 ,10)
}
 
// 时间格式化输出，如3:25:19 86。每10ms都会调用一次
function dateformat(micro_second) {
 // 秒数
 var second = Math.floor(micro_second / 1000);
 // 小时位
 var hr = Math.floor(second / 3600);
 // 分钟位
 var min = Math.floor((second - hr * 3600) / 60);
 // 秒位
 var sec = (second - hr * 3600 - min * 60);// equal to => var sec = second % 60;
 // 毫秒位，保留2位
 var micro_sec = Math.floor((micro_second % 1000) / 10);
 return hr + ":" + min + ":" + sec + " " + micro_sec;
}
 
Page({
 data: {
 clock: ''
 },
 onLoad: function() {
 countdown(this);
 }
});