JS实现十分钟倒计时代码实例

<body>
 <div id="timer"></div>
 <div id="warring"></div>
</body>

<script type="text/javascript">
 var maxtime = 10 * 60; // 
      function CountDown() {
        if (maxtime >= 0) {
          minutes = Math.floor(maxtime / 60);
          seconds = Math.floor(maxtime % 60);
          msg = "距离结束还有" + minutes + "分" + seconds + "秒";
          document.all["timer"].innerHTML = msg;
          if (maxtime == 5 * 60)alert("距离结束仅剩5分钟");
            --maxtime;
        } else{
          clearInterval(timer);
          alert("时间到，结束!");
        }
      }
      timer = setInterval("CountDown()", 1000);   
 </script>