jquery.focus.js

;(function($){

    $.fn.myfocus = function(options){

        var obj = $.extend({}, $.fn.myfocus.defaults, options || {});

        return $(this).each(function(){

            // methods.init();
            var $_this = $(this),
                 sWidth = $_this.width(),
                len = $_this.find('ul li').length,
                index = 0,
                picTimer;

            $_this.find('ul').width(sWidth*len);

            var btn = "<div class='btnBg'></div><div class='btn'>";
            for(var i=0; i < len; i++) {
                btn += "<span></span>";
            }
            btn += "</div><div class='preNext pre'></div><div class='preNext next'></div>";
            $_this.append(btn);

            $_this.find('.btn span').css("opacity",0.4).click(function() {
                index = $_this.find('.btn span').index(this);
                showPics(index);
            }).eq(0).trigger("click");

            $_this.hover(function(){
                clearInterval(picTimer);
            },function(){
                 picTimer = setInterval(function(){
                     showPics(index);
                     index++;
                     if(index == len) {index = 0}
                 },4000);
            });

            $_this.find('.pre').click(function() {
                index -= 1;
                if(index == -1) {index = len - 1;}
                showPics(index);
            });

            $_this.find('.next').click(function() {
                index += 1;
                if(index == len) {index = 0;}
                showPics(index);
            });

            function showPics(index) {         //普通切换
                var nowLeft = -index*sWidth; //根据index值计算ul元素的left值
                $_this.find('ul').stop(true,false).animate({"left":nowLeft},300); //通过animate()调整ul元素滚动到计算出的position
                //$(".focus .btn span").removeClass("on").eq(index).addClass("on"); //为当前的按钮切换到选中的效果
                $_this.find('.btn span').stop(true,false).animate({"opacity":"0.4"},300).eq(index).stop(true,false).animate({"opacity":"1"},300); //为当前的按钮切换到选中的效果
            }
                        
        });
    };

    $.fn.myfocus.defaults = {
        nextTarget : 10
    };


})(jQuery);

$('#focus').myfocus();

<div class="focus" id="focus">
        <ul>
            <li><a href="#" target="_blank"><img src="img/1.jpg" alt="" /></a></li>
            <li><a href="#" target="_blank"><img src="img/2.jpg" alt="" /></a></li>
            <li><a href="#" target="_blank"><img src="img/3.jpg" alt="" /></a></li>
        </ul>
</div>

<style type="text/css">

* {margin:0; padding:0;}
body {font-size:12px; color:#222; font-family:Verdana,Arial,Helvetica,sans-serif; background:#f0f0f0;}
.clearfix:after {content: "."; display: block; height: 0; clear: both; visibility: hidden;}
.clearfix {zoom:1;}
ul,li {list-style:none;}
img {border:0;}

.wrapper {width:800px; margin:0 auto; padding-bottom:50px;}

h1 {height:50px; line-height:50px; font-size:22px; font-weight:normal; font-family:"Microsoft YaHei",SimHei;}

.shuoming {margin-top:20px; border:1px solid #ccc; padding-bottom:10px;}
.shuoming dt {height:30px; line-height:30px; font-weight:bold; text-indent:10px;}
.shuoming dd {line-height:20px; padding:5px 20px;}

/* qqshop focus */
.focus {width:800px; height:450px; overflow:hidden; position:relative;}
.focus ul {height:450px; position:absolute;}
.focus ul li {float:left; width:800px; height:450px; overflow:hidden; position:relative;}
.focus ul li div {position:absolute; overflow:hidden;}
.focus .btnBg {position:absolute; width:800px; height:20px; left:0; bottom:0; background:#000;}
.focus .btn {position:absolute; width:780px; height:10px; padding:5px 10px; right:0; bottom:0; text-align:right;}
.focus .btn span {display:inline-block; _display:inline; _zoom:1; width:25px; height:10px; _font-size:0; margin-left:5px; cursor:pointer; background:#fff;}
.focus .btn span.on {background:#fff;}
.focus .preNext {width:45px; height:100px; position:absolute; top:90px; background:url(img/sprite.png) no-repeat 0 0; cursor:pointer;}
.focus .pre {left:0;}
.focus .next {right:0; background-position:right top;}
</style>