倒计时原理 

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="UTF-8">
 5         <title>倒计时原理</title>
 6         <script type="text/javascript">
 7             window.onload = function(){
 8                 var oP = document.getElementsByTagName('p')[0];
 9                 //var now = new Date();//Wed Apr 12 2017 16:21:09 GMT+0800 (中国标准时间)
10                 //console.log(now);
11                 //var setTime = new Date(2017,3,12,16,23,0);//Wed Apr 12 2017 16:23:00 GMT+0800 (中国标准时间)
12                 //注：时间中的月份是从数字0开始计数的，因此此例中2017,3,12代表Apr 12 2017
13                 //console.log(setTime);
14                 
15                 /*
16                 var now = new Date();
17                 var setTime = new Date('May 12 2017 16:21:00');
18                 */
19                 
20                 //console.log(setTime-now);//21080846532,返回毫秒数
21                 //console.log((setTime-now)/1000);//21080846.532,毫秒转化成秒
22                 //console.log(Math.floor((setTime-now)/1000));//去除小数点后的数值
23                 
24                 /*
25                 var t = Math.floor((setTime-now)/1000);
26                 
27                 var str = Math.floor(t/86400) + '天' + Math.floor(t%86400/3600) + '时' + Math.floor(t%86400%3600/60) + '分' + t%60 + '秒';
28                 
29                 console.log(str);
30                 
31                 */
32                 //天：Math.floor(t/86400)
33                 //时：Math.floor(t%86400/3600)
34                 //分：Math.floor(t%86400%3600/60)
35                 //秒：t%60
36                 
37                 
38                 // 数字形式：new Date( 2013,4,1,9,48,12 );
39                 // 字符串形式：new Date('June 10,2013 12:12:12');
40 
41                 //封装：
42                 oP.innerHTML = countdown();
43                 setInterval(function(){
44                     oP.innerHTML = countdown();
45                 },1000)
46                 function countdown(){
47                     var now = new Date();
48                     var setTime = new Date('May 12 2017 16:21:00');
49                     var t = Math.floor((setTime-now)/1000);
50                     var str = Math.floor(t/86400) + '天' + Math.floor(t%86400/3600) + '时' + Math.floor(t%86400%3600/60) + '分' + t%60 + '秒';
51                     return str;
52                 }
53             };
54         </script>
55     </head>
56     <body>
57         <p></p>
58     </body>
59 </html>

 

posted @ 2017-04-12 20:19  寒雨落轩  阅读(473)  评论(0)    收藏  举报