倒计时原生js

<!DOCTYPE html>

<html lang="en">

<head>

	<meta charset="UTF-8">

	<title>倒计时</title>

	<style type="text/css">

        body,div{margin:0;padding:0;font-family:"微软雅黑";font-size:16px;}

        #div1{letter-spacing:3px;width:300px;height:50px;position:absolute;left:50%;top:50%;margin-left:-150px;margin-top:-50px;background:#ff6000;line-height:50px;text-align:center;}

	</style>

</head>

<body>

	 <div id="div1">fr</div>

	 <script type="text/javascript">

	     function addZero(val){

	     	  return val<10?("0"+val):val

	     }

	     function getTimer(nowTime,targetTime){

	         if(targetTime>nowTime){

		          var spanTime = targetTime.getTime()-nowTime.getTime(); //

		          // 总的毫秒差 =指定时间距离1970.1.1的毫秒差 -当前时间距离1970.1.1的毫秒差

		          var spanDay = Math.floor(spanTime/(1000*60*60*24));    // 总的毫秒数换算成天数

		          var aDay = spanDay*24*60*60*1000;   // 天数占用的毫秒数

		          var spanHours = Math.floor((spanTime-aDay)/(1000*60*60)); //总的毫秒差 换算成小时

		          var aHours =spanHours*60*60*1000; // 小时占用的毫秒

		          var spanMinute = Math.floor((spanTime-aDay-aHours)/(1000*60)); //总的毫秒差换算成分钟

		          var aMinute = spanMinute*1000*60;  // 分钟暂用的毫秒数

		          var spanSec = Math.floor((spanTime-aDay-aHours-aMinute)/1000); //总的毫秒差换算成秒

		          var str = "倒计时："+addZero(spanDay)+"天"+addZero(spanHours)+"时"+addZero(spanMinute)+"分"+addZero(spanSec);

	          }else{

	          	  var str="00:00:00"

	          }

	          return str;

        }  

        var nowTime = new Date();  // 获取当前时间

        var targetTime = new Date("2015/4/23 01:00:00");  // 获取指定时间

        var oDiv =document.getElementById("div1");

        oDiv.innerHTML  =getTimer(nowTime,targetTime);

        var timer = setInterval(function(){

        	var nowTime = new Date();  // 获取当前时间

	        var targetTime = new Date("2015/4/23 01:00:00");  // 获取指定时间

	        var oDiv =document.getElementById("div1");

            oDiv.innerHTML=getTimer(nowTime,targetTime);

        },1000)

	 </script>

</body>

</html>
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