网页常用动态效果--放大镜

.box{
            width:350px;
            height:350px;
            background: url(images/xiaotu.jpg) 0 0 no-repeat;
            margin:100px;
            border:1px solid #000;
            position: relative;
        }
        .box span{
            width:150px;
            height:150px;
            background: red;
            position: absolute;
            left:0;
            top:0;
            opacity:0.3;
            cursor:move;
            display:none;
        }
        .box div{
            width:400px;
            height:400px;
            background: url(images/datu.jpg) 0 0 no-repeat;
            border:1px solid #000;
            position: absolute;
            right:-420px;
            top:0;
            display:none;
        }

 <script>
            //将span限制在box中拖拽，同时根据span拖拽的坐标来对应div大图中的坐标
            $(function(){
                var divX = $(‘.box‘).offset().left;
                var divY = $(‘.box‘).offset().top;
                var w1 = $(‘span‘).width();
                var h1 = $(‘span‘).height();
                var w2 = $(‘.box‘).width();
                var h2 = $(‘.box‘).height(); 
                $(‘.box‘).mouseover(function(event) {
                    $(‘.box span,.box div‘).show();
                    //鼠标移动
                    $(‘.box‘).mousemove(function(event) {
                        //获取鼠标坐标
                        var mx = event.pageX;
                        var my = event.pageY;
                        //拖拽点
                        var x = mx-divX-75;
                        var y = my-divY-75;
                        if(x<0){
                            x=0;
                        }
                        if(y<0){
                            y=0;
                        }
                        if(x>w2-w1){
                            x=w2-w1;
                        }
                        if(y>h2-h1){
                            y=h2-h1;
                        }
                        //对应div背景的坐标
                        var posX = 800*x/350;
                        var posY = 800*y/350;
                        $(‘span‘).css({left:x,top:y});
                        $(‘.box div‘).css({
                            backgroundPosition:(-posX)+‘px ‘+(-posY)+‘px‘
                        });
                    });
                });
                //离开box后，事件消失
                $(‘.box‘).mouseout(function(event) {
                    $(‘.box span,.box div‘).hide();
                });
            })
        </script>