jQuery实现的图片分组切换焦点图插件

 <div class="device">
        <h2>
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        <div class="scroll">
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  $(function () {
            var $number = Math.ceil($('.scroll ul li').length / 4); //获取滚动几屏个数
            var margin = 10; //设置图片间距
            var $w = $('.scroll li').width() + margin; // 一屏图片的宽度
            var $width = $w * $number * 2; //设置ul宽度
            var pre = $('.device .pre');
            var next = $('.device .next');
            if ($number == 1) { pre.hide(); next.hide(); }
            $('.scroll ul').width($width);
            var num = 0;
            function autoscroll() {
                num++;
                if ($number == 1) { return false }
                if (num == $number) {
                    num = 0;
                }
                var distance = -2 * $w * num;
                $('.scroll ul').stop().animate({ left: distance });
            }
            var scrollChange = setInterval(autoscroll, 8000);
            //鼠标悬停，暂停滚动
            $(".scroll ul,.pre,.next").mouseover(function () {
                $('.scroll ul').stop()
                clearInterval(scrollChange);
            });
            // 鼠标移走，滚动继续
            $('.scroll ul,.pre,.next').mouseout(function () {
                scrollChange = setInterval(autoscroll, 8000);
            });
            //下一组
            next.click(function () {
                num++;
                if (num >= $number) { num = 0 }
                var leftdis = -2 * $w * num;
                $('.scroll ul').stop().animate({ left: leftdis });
            });
            //上一组
            pre.click(function () {
                num--;
                if (num < 0) { num = $number - 1 }
                var rightdis = -2 * $w * num;
                $('.scroll ul').stop().animate({ left: rightdis });
            });
        });