图片轮播

图片切换原理:
在短时间内改变显示的图片的宽度

项目特色:
1.图片可以自动浏览, 时间间隔为5s
2.点击图片左右的箭头切换图片
3.点击图片下方的圈圈切换图片

项目知识点：
1.页面布局
2.点击响应
3.动画实现

项目优点：
通过代码获取li数组，可移植性好。

动画实现原理：

项目效果图:

以下是【类淘宝大图切换.html】

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>类淘宝大图切换</title>
        <link rel="stylesheet" type="text/css" href="类淘宝大图切换.css">
        <script language="javascript" type="text/javascript" src="类淘宝大图切换.js"></script>
    </head>

    <body>
        <div id="mainDiv">
            <div id="mainImage">

                <ul>
                    <li><img src="1.png"></li>
                    <li><img src="2.jpg"></li>
                    <li><img src="3.jpg"></li>
                    <li><img src="4.jpg"></li>
                </ul>
            </div>

            <div id="prev"><a href="javascript:;"><</a></div>   
            <div id="next"><a href="javascript:;">></a></div>   
            <div id="smallImage">
                <ul>
                    <li class="currentImage"><a href="#"><div id="circle1" ></div></a></li>
                    <li><a href="#"><div id="circle2"  ></div></a></li>
                    <li><a href="#"><div id="circle3"  ></div></a></li>
                    <li><a href="#"><div id="circle4"  ></div></a></li>
                </ul>
            </div>

        </div>

    </body>


</html>

接下来是【类淘宝大图切换.css】

ul,li{
    list-style-type:none;
    padding:0px;                        /*清除ul和li的缩进, 否则li的内容会向右后*/
    margin:0px;
}

#mainDiv{
    position:relative;
    width:1000px;
    height:500px;
    background-color:pink;
    overflow:hidden;                    /*在图片流中只显示当前选中的图片*/
    margin:20px 0 1px 2px;
}

#mainImage{
    position:absolute;
    width:4000px;                       /*此处是mainDiv的倍数宽度*/
    height:500px;
}

#prev{                                  /*向前的按钮*/
    position: absolute;
    width: 50px;    
    height: 50px;   
    top:225px;        
    left: 10px;
}

#next{                                  /*向后的按钮*/
    position: absolute; 
    width: 50px;    
    height: 50px;   
    top:225px;        
    left:930px;
}

#prev a, #next a{
    width: 50px;    
    height: 50px;   
    /*background: rgba(240,240,240,0.5);    
    border: 3px #fff solid; */
    font-size: 40px;    
    font-weight: bold;        
    color: silver;        
    text-align: center;        
    position: absolute;        
    text-decoration: none;
}

#prev a:hover, #next a:hover{     
    color: #fff;        
}

#mainDiv li{
    float:left;
}

#mainDiv li img{
    width:1000px;
    height:500px;
}

#smallImage{
    position:absolute;
    width:1000px;
    height:25px;
    top:460px;
    left:400;
    text-align:center;
    /*background-color:silver;*/
}

#smallImage ul{
    padding-left:355px;
}

#smallImage li{
    display:inline;
    float:left;
    margin:0 15px;
    padding-top:12px;
}

#smallImage li div{
    width:20px;
    height:20px;
    /*border:2px solid silver;*/
}

#circle1 {                                      /*圈圈索引*/
    width: 10px; 
    height: 10px; 
    background: silver; 
    -moz-border-radius: 50px; 
    -webkit-border-radius: 50px; 
    border-radius: 50px; 
    border:2px solid silver;
}

#circle2 {
    width: 10px; 
    height: 10px; 
    background: silver; 
    -moz-border-radius: 50px; 
    -webkit-border-radius: 50px; 
    border-radius: 50px; 
    border:2px solid silver;
}

#circle3 {
    width: 10px; 
    height: 10px; 
    background: silver; 
    -moz-border-radius: 50px; 
    -webkit-border-radius: 50px; 
    border-radius: 50px; 
    border:2px solid silver;
}

#circle4 {
    width: 10px; 
    height: 10px; 
    background: silver; 
    -moz-border-radius: 50px; 
    -webkit-border-radius: 50px; 
    border-radius: 50px; 
    border:2px solid silver;
}

接下来是【类淘宝大图切换.js】

var smallIDList;                                    //圈圈代表的ID列表
var focusList;                                      //圈圈所在的列表

function $(id){
    return document.getElementById(id);
}

function moveElement(elmentId, finalX, finalY, interval){
    if(!document.getElementById)
        return false;
    if(!document.getElementById(elmentId))
        return false;

    var elem = document.getElementById(elmentId);

    if(elem.movement){                          //若当前elementId有活动, 使其停止
        clearTimeout(elem.movement);
    }
    if(!elem.style.left){                       //到达最左端
        elem.style.left = "0px";
    }
    if(!elem.style.top){
        elem.style.top = "0px";
    }

    var xpos = parseInt(elem.style.left);
    var ypos = parseInt(elem.style.top);

    if(xpos == finalX && ypos == finalY)
        return true;
    if(xpos < finalX){
        var dist = Math.ceil((finalX-xpos)/10);
        xpos+=dist;
    }
    if(xpos > finalX){
        var dist = Math.ceil((xpos-finalX)/10);
        xpos-=dist;
    }
    if(ypos < finalY){
        var dist = Math.ceil((finalY-ypos)/10);
        ypos+=dist;
    }
    if(ypos > finalY){
        var dist = Math.ceil((ypos-finalY)/10);
        ypos-=dist;
    }

    elem.style.left = xpos + 'px';
    elem.style.top = ypos + 'px';

                                            //设置重复的定时器在短时间内(如5毫秒)不断刷新文职, 结果表现为图片移动
    var repeat = "moveElement('"+elmentId+"',"+finalX+","+finalY+","+interval+")";
    elem.movement = setTimeout(repeat,interval);
}


function clearCurrentImageTag(){            /*清空下方小图片的“current”位置标示*/
    for(var i=0; i<focusList.length; i++){
        focusList[i].className='';
        smallIDList[i].background="silver";
        smallIDList[i].width='10px';
        smallIDList[i].height='10px';
    }
}

function arrowChange(){
    var currentPrev=document.getElementById("prev");
    var currentNext=document.getElementById("next");   
    currentPrev.onclick = function(){       //前一个
        changeCurrentTag(1);
    }
    currentNext.onclick = function(){       
        changeCurrentTag(2);
    }   
}

function changeCurrentTag(moveFlag){
    if(!document.getElementById)
        return false;
    if(!document.getElementById('mainImage'))
        return false;
    var tempElem = document.getElementById('mainImage');

    var tempCurrentNum;
    for(i=0; i<focusList.length; i++){
        if(focusList[i].className == 'currentImage')
            tempCurrentNum=i;               //记录要显示的主图
    }
    if(moveFlag == 1){
        if(tempCurrentNum>0){
            tempCurrentNum = tempCurrentNum - 1;
        }   
    }else if(moveFlag == 2){
        if(tempCurrentNum<(focusList.length-1)){
            tempCurrentNum = tempCurrentNum + 1;
        }
    }

    moveElement('mainImage',tempCurrentNum*(-1000),0,5);        
    clearCurrentImageTag();
    focusList[tempCurrentNum].className='currentImage';
    smallIDList[tempCurrentNum].background='white';
    smallIDList[tempCurrentNum].width='13px';
    smallIDList[tempCurrentNum].height='13px';
}



function focusChange(){                     /*点击圆圈图片使之滚动*/
    for(i=0; i<focusList.length; i++){
        focusList[i].onclick=function(){
            var index = findIndex(this);
            moveElement('mainImage',index*(-1000),0,5);
            clearCurrentImageTag();
            focusList[index].className='currentImage';
            smallIDList[index].background='white';
            smallIDList[index].width='13px';
            smallIDList[index].height='13px';
        }
    }

    moveElement('mainImage',0,0,5);         //初始化圈圈
    clearCurrentImageTag();
    focusList[0].className='currentImage';
    smallIDList[0].background='white';
    smallIDList[0].width='13px';
    smallIDList[0].height='13px';
}

function findIndex(elem){
    for(i=0; i<focusList.length;i++){
        if(focusList[i]==elem)
           return i;
    }
    return -1;
}

setInterval('autoFocusChange()',5000);  

function autoFocusChange(){
    for(i=0; i<focusList.length; i++){
        if(focusList[i].className == 'currentImage')
            var currentNum=i;               //记录要显示的主图
    }
    currentNum = (currentNum+1)%(focusList.length);
    moveElement('mainImage',currentNum*(-1000));
    clearCurrentImageTag();     
    focusList[currentNum].className='currentImage';
    smallIDList[currentNum].background='white';
    smallIDList[currentNum].width="13px";
    smallIDList[currentNum].height="13px";
}

window.onload=function(){
    focusList = $('smallImage').getElementsByTagName('li');
    smallIDList = [(document.getElementById('circle1')).style,(document.getElementById('circle2')).style,
    (document.getElementById('circle3')).style,(document.getElementById('circle4')).style];

    focusChange();
    arrowChange();
}