倒计时组件：

function Countdown(leavetime) {        this._init(leavetime);    }  Countdown.prototype = {      _init : function (leavetime) {          this.timer = null;          this.leavetime = leavetime || 0;          this.clock = {};          this.clock.leavetimeSec = Math.floor(this.leavetime / 1000);      },      _format : function () {          this.clock.sec = this.clock.leavetimeSec % 3600 % 60;          this.clock.min = Math.floor(this.clock.leavetimeSec % 3600 / 60);          this.clock.hours = Math.floor(this.clock.leavetimeSec / 3600);          this.clock.secStr = String(this.clock.sec).length == 1 ? ('0' + this.clock.sec) : String(this.clock.sec);          this.clock.minStr = String(this.clock.min).length == 1 ? ('0' + this.clock.min) : String(this.clock.min);          this.clock.hourStr = String(this.clock.hours).length == 1 ? ('0' + this.clock.hours) : String(this.clock.hours);      },      run : function (doFn, endFn) {          var that = this;          this._format();          doFn(this.clock);          if (this.clock.leavetimeSec == 0) {              clearTimeout(this.timer);              endFn(this.clock);              return this;          }          this.clock.leavetimeSec --;          this.timer = setTimeout(function () {              that.run(doFn, endFn);          }, 1000)      }  };

 

使用：（为说明使用，运用了jquery获取dom对象）

html: 
     
var Countdown = new Countdown(30000000); // 实例化倒计时// 运行倒计时Countdown.run(function (clock) { // clock 是个对象 挂载着小时 分钟 秒钟    $('#box').text(clock.hourStr + ':' + clock.minStr + ':' + clock.secStr);  }, function () { // 这里写倒计时到点的callback    alert('结束了！')  });