时分秒特效00:20:08

  var hour,minute,second,alltime;//时 分 秒
  hour=minute=second=alltime=0;//初始化
  var timer=null;  //定时器 
  startTimekeeper()
  function startTimekeeper(){
   timer=setTimeout(function(){
     timeKeeper();
     setTimeout(startTimekeeper(),1000)
   },1000)
  }
 function timeKeeper(){
  alltime++;
  hour=Math.floor(alltime/60/60);
  minute=Math.floor(alltime/60%60);
  second=Math.floor(alltime%60);
  if(hour<10){
        hour = "0" + hour;
  }
  if(minute<10){
      minute = "0" + minute;
  }
  if(second<10){
        second = "0" + second;
  }
  console.log(hour+':'+minute+':'+second);
}