Javascript 图片左右滑动与切换

Html代码 ：

<div class="v_out v_out_p">
<div class="prev">
<a href="javascript:void(0)"></a>
</div>
<div class="v_show">
<div class="v_cont">
<ul>
<li index="0" style="background: #f00">[第1讲]</li>
<li index="1" style="background: #ff0">[第2讲]</li>
<li index="2" style="background: #f0f">[第3讲]</li>
<li index="3" style="background: #999">[第4讲]</li>
<li index="4" style="background: #666">[第5讲]</li>
</ul>
</div>
</div>
<div class="next">
<a href="javascript:void(0)"></a>
</div>
<ul class="circle">
<li class="circle-cur">1</li>
<li>2</li>
<li>3</li>
<li>4</li>
<li>5</li>
</ul>
</div>
<script type="text/javascript">

$(function () {

/*======next======*/
$(".next a").click(function () { nextscroll() });

function nextscroll() {

var vcon = $(".v_cont ");
var offset = ($(".v_cont li").width()) * -1;

vcon.stop().animate({ left: offset }, "slow", function () {

var firstItem = $(".v_cont ul li").first();
vcon.find("ul").append(firstItem);
$(this).css("left", "0px");

circle()

});

};

function circle() {

var currentItem = $(".v_cont ul li").first();
var currentIndex = currentItem.attr("index");

$(".circle li").removeClass("circle-cur");
$(".circle li").eq(currentIndex).addClass("circle-cur");

}

//setInterval(nextscroll,2000)

/*======prev======*/
$(".prev a").click(function () {

var vcon = $(".v_cont ");
var offset = ($(".v_cont li").width() * -1);

var lastItem = $(".v_cont ul li").last();
vcon.find("ul").prepend(lastItem);
vcon.css("left", offset);
vcon.animate({ left: "0px" }, "slow", function () {
circle()
})

});

/*======btn====circle======*/
var animateEnd = 1;

$(".circle li").click(function () {

if (animateEnd == 0) { return; }

$(this).addClass("circle-cur").siblings().removeClass("circle-cur");

var nextindex = $(this).index();
var currentindex = $(".v_cont li").first().attr("index");
var curr = $(".v_cont li").first().clone();

if (nextindex > currentindex) {

for (var i = 0; i < nextindex - currentindex; i++) {

var firstItem = $(".v_cont li").first();
$(".v_cont ul").append(firstItem);

}

$(".v_cont ul").prepend(curr);

var offset = ($(".v_cont li").width()) * -1;

if (animateEnd == 1) {

animateEnd = 0;
$(".v_cont").stop().animate({ left: offset }, "slow", function () {

$(".v_cont ul li").first().remove();
$(".v_cont").css("left", "0px");
animateEnd = 1;

});

}

} else {

var curt = $(".v_cont li").last().clone();

for (var i = 0; i < currentindex - nextindex; i++) {
var lastItem = $(".v_cont li").last();
$(".v_cont ul").prepend(lastItem);
}

$(".v_cont ul").append(curt);

var offset = ($(".v_cont li").width()) * -1;

$(".v_cont").css("left", offset);

if (animateEnd == 1) {

animateEnd = 0;
$(".v_cont").stop().animate({ left: "0px" }, "slow", function () {

$(".v_cont ul li").last().remove();
animateEnd = 1;
});
}
}
});
})
</script>

============================================================================================================

css代码：

*
{
margin: 0px;
padding: 0px;
list-style-type: none;
}
.v_out
{
width: 748px;
margin: 20px auto;
overflow: hidden;
}
.v_show
{
width: 665px;
overflow: hidden;
position: relative;
height: 280px;
float: left;
}
.v_cont
{
width: 6650px;
position: absolute;
left: 0px;
top: 0px;
}
.v_cont ul
{
float: left;
text-align: center;
line-height: 50px;
}
.v_cont ul li
{
width: 665px;
height: 250px;
background: #f8f8f8;
float: left;
margin-top: 3px;
}

/*---圆圈---*/
.v_out_p
{
position: relative;
overflow: visible;
}
.circle
{
position: absolute;
left: 40px;
top: 290px;
}
.circle li
{
width: 120px;
height: 60px;
float: left;
margin-right: 10px;
background: #ccc;
}
.circle .circle-cur
{
background: #f00;
}

/*---切换---*/
.prev, .next
{
float: left;
padding: 105px 9px 0;
}
.prev a
{
background: #f00;
}
.prev .ico_1
{
background: url(input_a.gif) no-repeat 0 -3757px;
}

.next a
{
background: #f00;
}
.next .ico_2
{
background: url(input_a.gif) no-repeat right -3757px;
}
.prev, .prev a, .next, .next a
{
width: 21px;
height: 28px;
display: block;
}