动态倒计时JavaScript

纯JavaScript，动态显示倒计时，粘到notepad就能用

<div>   Registration closes in <span id="timer">02:00<span> minutes!</div><script>   window.onload = function(){     var hour = 1;     var sec = 59;     var refreshId = setInterval(function(){       document.getElementById("timer").innerHTML = hour +" : " + sec ;       sec--;       if(sec==0){          if(hour>0){            hour--;            sec=59;          }else{            clearInterval(refreshId);            setTimeout(function() {                document.getElementById("timer").innerHTML = 0 +" : " + 0 ;            }, 1000);          }       }      },1000);    }</script>