自己用原生js写的简单焦点图，算是对原生js初步运用。

html部分

 div 
 section id="mPhoto" 
 img src="images//b_5809b93b66d18.jpg"/ 
 /section !-- 主要的大图 -- 
 section 
 div 
 section 
 img src="images//b_5809b93b66d18.jpg"/ 
 /section 
 section 
 img src="images//b_5809b96c4da53.jpg"/ 
 /section 
 section 
 img src="images//b_5809b9bea39c4.jpg"/ 
 /section 
 section 
 img src="images//b_5809ba288384e.jpg"/ 
 /section 
 section 
 img src="images//b_5809bae42fa81.jpg"/ 
 /section 
 section 
 img src="images//b_5809ba288384e.jpg"/ 
 /section 
 section 
 img src="images//b_5809bb3da0bbc.jpg"/ 
 /section 
 /div 
 /section !-- 其他的小图 -- 
 section 
 div 
 i /i 
 /div !-- 上一张 -- 
 div 
 i /i 
 /div !-- 下一张 -- 
 /section !-- 上下翻页 -- 
 /div !-- 焦点图区 -- 

js部分

window.onload = function(){

 var mPhoto = document.getElementById("mPhoto");
 var imgWrap = document.getElementsByClassName("imgWrap")[0];
 var wrapSize = 4; /*图片容器最大显示图片数*/
 if(imgWrap.getElementsByTagName("section").length wrapSize){
 imgWrap.innerHTML = imgWrap.innerHTML+imgWrap.innerHTML;
 var oImages = imgWrap.getElementsByTagName("section");
 for(var i = 0 ; i oImages.length; i++)
 oImages[i].onmouseover = function()
 for(var j = 0 ; j oImages.length; j++)
 removeClass(oImages[j],"on");
 var imgSrc = this.getElementsByTagName("img")[0].src;
 addClass(this,"on");
 mPhoto.getElementsByTagName("img")[0].src = imgSrc;

 var oPrevNext = document.getElementsByClassName("prevNext")[0];
 var oPrev = oPrevNext.getElementsByClassName("prev")[0];
 var oNext = oPrevNext.getElementsByClassName("next")[0];
 var oImageHeight = oImages[0].getElementsByTagName("img")[0].height||0;
 var oPositionTop = imgWrap.offsetTop;
 var imgIndex = 0;
 if(oImages.length wrapSize*2)
 oPrev.style.display = "block";
 oNext.style.display = "block";
 /*上一页*/
 oPrev. unction()
 imgIndex-=1;
 if(imgIndex =0){
 imgIndex = 6;

 addClass(oImages[index],"on");
 var imgSrc = oImages[index].getElementsByTagName("img")[0].src;
 mPhoto.getElementsByTagName("img")[0].src = imgSrc;

 addClass(oImages[index],"on");
 var imgSrc = oImages[index].getElementsByTagName("img")[0].src;
 mPhoto.getElementsByTagName("img")[0].src = imgSrc;

{//检查class是否存在
 return !!element.className.match(new RegExp('(\\s|^)'+cName+'(\\s|$)'));
function addClass(element,cName)
{//添加一个class
 if(!hasClass(element,cName))
 element.className +=' '+cName;
function removeClass(element,cName)
{//移除一个class
 if(hasClass(element,cName))
 element.className = element.className.replace(new RegExp('(\\s|^)'+cName+'(\\s|$)'),' ');

.productInfo .prevNext div.prev i{
 background: url(../images/arrows-icon.png) 0 -16px no-repeat;
 background-size: 48px 32px;
 bottom: 2px;

.productInfo .prevNext div.next i{
 background: url(../images/arrows-icon.png) 0 0 no-repeat;
 background-size: 48px 32px;
 top: 2px;

.productInfo .prevNext div.prev:hover i{
 background: url(../images/arrows-icon.png) -16px -16px no-repeat;
 background-size: 48px 32px;

.productInfo .prevNext div.next:hover i{
 background: url(../images/arrows-icon.png) -16px 0px no-repeat;
 background-size: 48px 32px;

.productInfo .prevNext div.prev:active i{
 background: url(../images/arrows-icon.png) -32px -16px no-repeat;
 background-size: 48px 32px;

.productInfo .prevNext div.next:active i{
 background: url(../images/arrows-icon.png) -32px 0px no-repeat;
 background-size: 48px 32px;

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持凡科。