用javaScript實現輪播圖效果 包括自動變換，按鈕控制，上一張下一張切換

javaScript實現輪播圖效果（逆戰總結）

1.HTML代碼

<div id="wrap">
<img src="images/1.jpg" alt="" class="on">
<img src="images/2.jpg" alt="">
<img src="images/3.jpg" alt="">
<img src="images/4.jpg" alt="">
<div class="btn">
<span class="active"></span>
<span></span>
<span></span>
<span></span>
</div>
<i class="left" id="prev"></i>
<i class="right" id="next"></i>
</div>
2.css代碼

#wrap{
position: relative;
width:590px;
height: 470px;
}
#wrap img{
position: absolute;
top: 0;
left: 0;
/*display: none;*/
opacity: 0;

}
#wrap .on{
/*display: block;*/
transition: 2s;
opacity: 1;
}
.btn {
position: absolute;
bottom: 20px;
left: 50%;
margin-left: -44px;
}
.btn span{
float: left;
width: 8px;
height: 8px;
border:2px solid rgba(255,255,255,0.4);
border-radius: 5px;
margin-right: 10px;
}
.btn .active{
background: white;
cursor: pointer;
}
.left,.right{
display: block;
width: 37px;
height: 53px;
position: absolute;
top: 50%;
margin-top: -27px;
cursor: pointer;
}
.left{
background: url("images/arrow.png") left top;
}
.right{
background: url("images/arrow.png") left -53px;
right: 0;
}
3.js代碼

window.onload = function () {
var oWrap = document.getElementById('wrap');
var aImg = oWrap.getElementsByTagName('img');
var aBtn = oWrap.getElementsByTagName('span');
var oPrev = document.getElementById('prev');
var oNext = document.getElementById('next');
var iNow =0;

function tab(){
for (var i =0;i<aBtn.length;i++){//清空所有按鈕選中樣式以及圖片顯示樣式
aBtn[i].className='';
aImg[i].className='';
}
aBtn[iNow].className='active';//設置當前按鈕選中樣式以及當前圖片透明度
aImg[iNow].className='on';
}

setInterval( function () {//每兩秒循環變換下一張圖片
iNow++;
if (iNow==aBtn.length)iNow=0;
tab();
},2000);

for (var i =0;i<aBtn.length;i++){
aBtn[i].index=i;//為按鈕添加自定義屬性（索引）目的是使圖片和按鈕相對應
//按鈕
aBtn[i].οnmοuseοver= function () {
iNow=this.index; //是按鈕所控制顯示的圖片與左右箭頭控制顯示的圖片相對應
tab();
}
//下一個箭頭
oNext.onclick = function () {
iNow++;
if (iNow==aImg.length)iNow=0;
tab();
}
//上一個箭頭
oPrev.onclick = function () {
iNow--;
if (iNow==-1)iNow=aImg.length-1;
tab();
}

}

}