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);
  }
});

/* 秒級倒計時 */
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)
}

/* 毫秒級倒計時 */
// 初始毫秒數(shù)，同時用作歸零
var micro_second_init = 100;
// 當前毫秒數(shù)
var micro_second_current = micro_second_init;
// 毫秒計時器
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個時鐘，影響性能，合并下去掉countdown，于是countdown4micro變成以下的樣子：

function countdown4micro(that) {

  var loop_second = Math.floor(loop_index / 100);
  // 得知經(jīng)歷了1s
  if (cost_micro_second != loop_second) {
    // 賦予新值
    cost_micro_second = loop_second;
    // 總秒數(shù)減1
    total_second--;

  }
   // 每隔一秒，顯示值減1; 渲染倒計時時鐘
  that.setData({
   clock:dateformat(total_second - 1)
  });

   if (total_second == 0) {
    that.setData({
     // micro_second: "",
     clock:"時間到"
    });
    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++，不然時鐘停止時還有10毫秒剩余
  loop_index ++;
  countdown4micro(that);
 }
 ,10)
}

/** 
 * 需要一個目標日期，初始化時，先得出到當前時間還有剩余多少秒
 * 1.將秒數(shù)換成格式化輸出為XX天XX小時XX分鐘XX秒 XX
 * 2.提供一個時鐘，每10ms運行一次，渲染時鐘，再總ms數(shù)自減10
 * 3.剩余的秒次為零時，return，給出tips提示說，已經(jīng)截止
 */

// 定義一個總毫秒數(shù)，以一分鐘為例。TODO，傳入一個時間點，轉(zhuǎn)換成總毫秒數(shù)
var total_micro_second = 2 * 1000;

/* 毫秒級倒計時 */
function countdown(that) {
   // 渲染倒計時時鐘
   that.setData({
     clock:dateformat(total_micro_second)
   });

   if (total_micro_second <= 0) {
     that.setData({
       clock:"已經(jīng)截止"
     });
     // timeout則跳出遞歸
     return ;
   }  
   setTimeout(function(){
    // 放在最后--
    total_micro_second -= 10;
    countdown(that);
  }
  ,10)
}

// 時間格式化輸出，如3:25:19 86。每10ms都會調(diào)用一次
function dateformat(micro_second) {
   // 秒數(shù)
   var second = Math.floor(micro_second / 1000);
   // 小時位
   var hr = Math.floor(second / 3600);
   // 分鐘位
   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);
  }
});