Javascript无缝左右滚动

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >
< html  xmlns ="http://www.w3.org/1999/xhtml" >
< head >
< meta  http-equiv ="Content-Type"  content ="text/html; charset=gb2312"   />
< title ></ title >
</ head >
< body >

< script  type ="text/javascript" >
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, idScrollLeft, idScrollRight, options) {
    var oScroll = this, oScroller = $(idScroller), oScrollMid = $(idScrollMid);
    
    this.widthScroller = oScroller.offsetWidth;
    this.widthList = oScrollMid.offsetWidth;
    
    if(this.widthList <= this.widthScroller) return;
    
    oScroller.style.overflow = "hidden";
    oScrollMid.appendChild(oScrollMid.cloneNode(true));
    
    this.oScroller = oScroller;
    this.scroll = true;
    
    this.SetOptions(options);
    
    this.side = 1;//1是左 -1是右
    switch (this.options.Side) {
        case "right" :
            this.side = -1;
            break;
        case "left" :
        default :
            this.side = 1;
    }
    
    addEventHandler(oScrollMid , "mouseover", function() { oScroll.scroll = false; });
    addEventHandler(oScrollMid , "mouseout", function() { oScroll.scroll = true; });
    
    if(idScrollLeft) { addEventHandler($(idScrollLeft), "click", function() { oScroll.side = 1; }); }
    if(idScrollRight) { addEventHandler($(idScrollRight), "click", function() { oScroll.side = -1; }); }
    
    this.Scroll();
  },
  //设置默认属性
  SetOptions: function(options) {
    this.options = {//默认值
      Step:            1,//每次变化的px量
      Time:            50,//速度
      Side:            "left"//默认滚动方向
    };
    Object.extend(this.options, options || {});
  },
  //滚动
  Scroll: function() {
    if (this.scroll) {
        var iScroll = this.oScroller.scrollLeft, iWidth = this.widthList;
        if(this.side > 0){
            if(iScroll >= (iWidth * 2 - this.widthScroller)){ iScroll -= iWidth; }
        } else {
            if(iScroll <= 0){ iScroll += iWidth; }
        }
        this.oScroller.scrollLeft = iScroll + this.options.Step * this.side;//注意scrollLeft超过1400会自动变回1400 注意长度
    }
    var oScroll = this; window.setTimeout(function(){ oScroll.Scroll(); }, this.options.Time);
  }
};

window.onload = function(){
    new Scroller("idScroller","idScrollMid", "idScrollLeft", "idScrollRight");
}
</ script >
< div  id ="idScroller"  style ="width:290px; overflow:hidden" >
< div  style ="width:2000px" >
     < div  id ="idScrollMid"  style ="float:left;" >
       < div  style ="float:left" >   < img  src ="1.jpg"  width ="150px"  height ="150px;" />   </ div >
       < div  style ="float:left" >   < img  src ="1.jpg"  width ="150px"  height ="150px;" />   </ div >
     </ div >
</ div >
</ div >
< input  id ="idScrollLeft"  type ="button"  value ="向左"   />
< input  id ="idScrollRight"  type ="button"  value ="向右"   />
</ body >
</ html >