var $ = function (id) { 
    return "string" == typeof id ? document.getElementById(id) : id; 
}; 

var Class = { 
  create: function() { 
    return function() { 
      this.initialize.apply(this, arguments); 
    } 
  } 
} 

Object.extend = function(destination, source) { 
    for (var property in source) { 
        destination[property] = source[property]; 
    } 
    return destination; 
} 

function addEventHandler(oTarget, sEventType, fnHandler) { 
    if (oTarget.addEventListener) { 
        oTarget.addEventListener(sEventType, fnHandler, false); 
    } else if (oTarget.attachEvent) { 
        oTarget.attachEvent("on" + sEventType, fnHandler); 
    } else { 
        oTarget["on" + sEventType] = fnHandler; 
    } 
}; 


var Scroller = Class.create(); 
Scroller.prototype = { 
  initialize: function(idScroller, idScrollMid, options) { 
    var oScroll = this, oScroller = $(idScroller), oScrollMid = $(idScrollMid); 
     
    this.heightScroller = oScroller.offsetHeight; 
    this.heightList = oScrollMid.offsetHeight; 
     
    if(this.heightList <= this.heightScroller) return; 
     
    oScroller.style.overflow = "hidden"; 
    oScrollMid.appendChild(oScrollMid.cloneNode(true)); 
     
    this.oScroller = oScroller;     
    this.timer = null; 
     
    this.SetOptions(options); 
     
    this.side = 1;//1是上 -1是下 
    switch (this.options.Side) { 
        case "down" : 
            this.side = -1; 
            break; 
        case "up" : 
        default : 
            this.side = 1; 
    } 
     
    addEventHandler(oScrollMid , "mouseover", function() { oScroll.Stop(); }); 
    addEventHandler(oScrollMid , "mouseout", function() { oScroll.Start(); }); 
     
    if(this.options.PauseStep <= 0 || this.options.PauseHeight <= 0) this.options.PauseStep = this.options.PauseHeight = 0; 
    this.Pause = 0; 
     
    this.Start(); 
  }, 
  //设置默认属性 
  SetOptions: function(options) { 
    this.options = {//默认值 
      Step:            1,//每次变化的px量 
      Time:            60,//速度(越大越慢) 
      Side:            "up",//滚动方向:"up"是上，"down"是下 
      PauseHeight:    0,//隔多高停一次 
      PauseStep:    1000//停顿时间(PauseHeight大于0该参数才有效) 
    }; 
    Object.extend(this.options, options || {}); 
  }, 
  //滚动 
  Scroll: function() { 
    var iScroll = this.oScroller.scrollTop, iHeight = this.heightList, time = this.options.Time, oScroll = this, iStep = this.options.Step * this.side; 
     
    if(this.side > 0){ 
        if(iScroll >= (iHeight * 2 - this.heightScroller)){ iScroll -= iHeight; } 
    } else { 
        if(iScroll <= 0){ iScroll += iHeight; } 
    } 
     
    if(this.options.PauseHeight > 0){ 
        if(this.Pause >= this.options.PauseHeight){ 
            time = this.options.PauseStep; 
            this.Pause = 0; 
        } else { 
            this.Pause += Math.abs(iStep); 
            this.oScroller.scrollTop = iScroll + iStep; 
        } 
    } else { this.oScroller.scrollTop = iScroll + iStep; } 
     
    this.timer = window.setTimeout(function(){ oScroll.Scroll(); }, time); 
  }, 
  //开始 
  Start: function() { 
    this.Scroll(); 
  }, 
  //停止 
  Stop: function() { 
    clearTimeout(this.timer); 
  } 
};