原生javascript实现图片按钮切换

function LGY_picSwitch(option){
    this.oWrap = this.getId(option.wrapID); //最外层元素
    this.olistWrap = this.getNodeByClassname(this.oWrap,'gy_picSwitch_listWrap')[0];
    this.oUl = this.olistWrap.getElementsByTagName('ul')[0];
    this.oBtnPrev = this.getNodeByClassname(this.oWrap,'gy_picSwitch_prev')[0];
    this.oBtnNext = this.getNodeByClassname(this.oWrap,'gy_picSwitch_next')[0];
    this.nLen = this.oUl.getElementsByTagName('li').length; //图片总数
    this.nScollCount = option.scrollCount; //每次滚动的数量
    this.nScollLen = Math.ceil(this.nLen/option.scrollCount); // 切换判断的最大值
    this.nSwitchWidth = 0; //每次切换移动的距离，在代码里面动态获取值
    this.nIndex = 0; //切换图片的当前索引
    this.timer = null; //切换图片的引值
    this.int();
}
LGY_picSwitch.prototype = {
    getId:function(id){
        return document.getElementById(id);
    },
    getNodeByClassname:function(parent,classname){
        var classElements = new Array();
        var els = parent.getElementsByTagName('*');
        var elsLen = els.length;
        var pattern = new RegExp("(^|\s)"+classname+"(\s|$)");
        for (i = 0, j = 0; i < elsLen; i++) {
                if ( pattern.test(els[i].className) ) {
                        classElements[j] = els[i];
                        j++;
                }
        }
        return classElements;
    },
    getCss:function(node,value)
    {
        return node.currentStyle?node.currentStyle[value]:getComputedStyle(node,null)[value];
    },
    setCss:function(node,val){
        for(var v in val){
            node.style.cssText += ';'+ v +':'+val[v];
        }
    },
    moveFn:function(node,value,targetValue,callback){
        var _that = this;
        clearInterval(this.timer);
        this.timer = setInterval(function()
        {
            var val = parseFloat(_that.getCss(node,value));
            var speed = ( targetValue- val )/8;
            speed = speed>0?Math.ceil(speed):Math.floor(speed);
            if(speed ==0)
            {
                clearInterval(_that.timer);
                callback&&callback();
            }
            else
            {                   
                node.style[value] = ( val + speed ) +'px';                   
            }
           
        },20);
    },
    picChange:function(){
        this.moveFn(this.oUl,'marginLeft',-this.nIndex*this.nSwitchWidth);
    },
    cancelBubble:function(e){
        e.stopPropagation?e.stopPropagation():e.cancelBubble = true;
    },
    btnIsShow:function(){
        this.setCss(this.oBtnNext,{'display':'block'});
        this.setCss(this.oBtnPrev,{'display':'block'});
        if( this.nIndex == 0 ) this.setCss(this.oBtnPrev,{'display':'none'});
        if( this.nIndex ==(this.nScollLen-1) ) this.setCss(this.oBtnNext,{'display':'none'});
    },
    btnPrev:function(){
        var _that = this;
        this.oBtnPrev.onclick = function(e){
            var e = e || window.event;
            _that.cancelBubble(e);
            if(_that.nIndex != 0 ) {
                _that.nIndex--;
                _that.picChange();
                _that.btnIsShow();
            }
        }
    },
    btnNext:function(){
        var _that = this;
        this.oBtnNext.onclick = function(e){
            var e = e || window.event;
            _that.cancelBubble(e);
            if(_that.nIndex != (_that.nScollLen-1) ) {
                _that.nIndex++;
                _that.picChange();
                _that.btnIsShow();
            }
        }
    },
    int:function(){
        //动态获取移动的宽度
        var oLi = this.oUl.getElementsByTagName('li')[0],
            oLi_w = oLi.offsetWidth + parseInt(this.getCss(oLi,'marginLeft')) + parseInt(this.getCss(oLi,'marginRight'));
        this.nSwitchWidth = oLi_w*this.nScollCount;
        //按钮显示初始化
        this.btnIsShow();
        //左右切换
        this.btnPrev();
        this.btnNext();
    }
}

/*
* HTML结构必需是以下：外层ID名，自己传入 如下面的：id="gy_picSwitch02" ，ID名，自己随便给
但，里面的结构必需一样，包括类名classname
<div id="gy_picSwitch02">
    <span class="gy_picSwitch_prev"></span>
    <span class="gy_picSwitch_next"></span>
    <div class="gy_picSwitch_listWrap">
        <ul>
            <li><img src="images/pic01.jpg" alt=""></li>
            <li><img src="images/pic02.jpg" alt=""></li>
            <li><img src="images/pic03.jpg" alt=""></li>
            <li><img src="images/pic04.jpg" alt=""></li>
            <li><img src="images/pic05.jpg" alt=""></li>
            <li><img src="images/pic06.jpg" alt=""></li>
            <li><img src="images/pic07.jpg" alt=""></li>
            <li><img src="images/pic08.jpg" alt=""></li>
        </ul>
    </div>
</div>

  
*
*/
//实例化
 new LGY_picSwitch({'wrapID':'gy_picSwitch','scrollCount':5});