最近做浏览器界面倒计时，用js就实现，两种方式：
一：设置时长，进行倒计时。比如考试时间等等
代码如下：
1 <html> 2 <head> 3 <meta charset="UTF-8"> 4 <title>简单时长倒计时</title> 5 <SCRIPT type="text/javascript"> 6 var maxtime = 60 * 60; //一个小时，按秒计算，自己调整! 7 function CountDown() { 8 if (maxtime >= 0) { 9 minutes = Math.floor(maxtime / 60); 10 seconds = Math.floor(maxtime % 60); 11 msg = "距离结束还有" + minutes + "分" + seconds + "秒"; 12 document.all["timer"].innerHTML = msg; 13 if (maxtime == 5 * 60)alert("还剩5分钟"); 14 --maxtime; 15 } else{ 16 clearInterval(timer); 17 alert("时间到，结束!"); 18 } 19 } 20 timer = setInterval("CountDown()", 1000); 21 </SCRIPT> 22 </head> 23 <body> 24 <div id="timer" style="color:red"></div> 25 <div id="warring" style="color:red"></div> 26 </body> 27 </html>
运行结果：
二：设置时间戳，进行倒计时。比如距离活动结束时间等等
代码如下：
1 <html> 2 <head> 3 <meta charset="UTF-8"> 4 <title>js简单时分秒倒计时</title> 5 <script type="text/javascript"> 6 function countTime() { 7 //获取当前时间 8 var date = new Date(); 9 var now = date.getTime(); 10 //设置截止时间 11 var str="2018/3/17 00:00:00"; 12 var endDate = new Date(str); 13 var end = endDate.getTime(); 14 15 //时间差 16 var leftTime = end-now; 17 //定义变量 d,h,m,s保存倒计时的时间 18 var d,h,m,s; 19 if (leftTime>=0) { 20 d = Math.floor(leftTime/1000/60/60/24); 21 h = Math.floor(leftTime/1000/60/60%24); 22 m = Math.floor(leftTime/1000/60%60); 23 s = Math.floor(leftTime/1000%60); 24 } 25 //将0-9的数字前面加上0，例1变为01 26 d = checkTime(d); 27 h = checkTime(h); 28 m = checkTime(m); 29 s = checkTime(s); 30 function checkTime(i){ 31 if (i<10) { 32 i = "0"+i; 33 } 34 return i; 35 } 36 //将倒计时赋值到div中 37 document.getElementById("_d").innerHTML = d+"天"; 38 document.getElementById("_h").innerHTML = h+"时"; 39 document.getElementById("_m").innerHTML = m+"分"; 40 document.getElementById("_s").innerHTML = s+"秒"; 41 //递归每秒调用countTime方法，显示动态时间效果 42 setTimeout(countTime,1000); 43 44 } 45 </script> 46 </head > 47 <body onload="countTime()" > 48 <div> 49 <span id="_d">00</span> 50 <span id="_h">00</span> 51 <span id="_m">00</span> 52 <span id="_s">00</span> 53 </div> 54 </body> 55 </html>
运行结果：
