js倒计时(js倒计时5秒)

倒计时69天！大家倒计时多少天了？
我是倒计时90天了,很享受宝宝每天胎动的时间
什么是倒计时载入页面的JS代码？
  diffSecs = timeDiff/1000; //因为时间以毫秒为单位 return(this。diffSecs); //返回间隔秒数} function getSecs() { var mySecs = initStopwatch(); var mySecs1 = +mySecs; //以倒计时方式显示时间 mySecs1= 10 - eval（mySecs1。
js倒计时代码
离半夜12点还有
    
     小时
     
      分
     
    
function countdown() {
var today = new Date();
var h = today.getHours();
var m = today.getMinutes();
h = 23 - h;
m = 59 - m;
m = checkTime(m)
document.getElementById("hour").innerHTML=h;
document.getElementById("min").innerHTML=m;
}
function checkTime(i) {
if (i<10) i = "0" + i;
return i;
}
setInterval("countdown()", 50);
 
   
 小时 
     分 
    
 
   
function showtime(){
 var tartime = new Date();
 var nowtime = new Date();
 tartime.setHours(24,0,0,0);
 var tartime = tartime.getTime();
 var nowtime = nowtime.getTime();
 var time = tartime - nowtime;
 var seconds = Math.floor(time/1000);
 var mins = Math.floor(seconds/60);
 var hours = Math.floor(mins/60);
 var nowmins = mins%60;
 var nowsec = seconds%60;
 document.getElementById('hour').innerHTML = hours;
 document.getElementById('min').innerHTML = nowmins; 
 document.getElementById('sec').innerHTML = nowsec; 
showtime();
setInterval(showtime,1000);
还加了秒数。倒计时。放在body中
JS如何倒计时？
var t=60;
var a=setInterval(daojishi,1000);//1000毫秒
function daojishi(){
t--;
//刷新时间显示
if(t==0){
clearInterval(a);
//倒计时结束
}
}window.setTimeout("setPopTitle();",20*1000);
function setPopTitle()
{
alert("20秒到了");
}
如果是20秒后想调后台，就用ajax直接调