js实现放大镜效果

<div id="box"> ???????<img width="100%" height="100%" src="images/1.png" alt="#"> ???????<div id="move"></div> ?????</div> ???????<div id="bimg"> ?????????????<img id="b_bimg" src="images/1.png" alt="#"> ???????</div>

 ???????????*{ ?margin:0px; ?padding:0px;}#box{ ?width:330px; ?height:330px; float: left; ?margin-left:17%; ?position:relative;}#move{ ?background-image:url(images/move.png); ?width:100px; ?height:100px; ?position:absolute; ?left:0px; ?top:0px; ?display:none;}#bimg{ ?width:400px; ?height:400px; ?overflow:hidden; float: left; margin-left: 20px; ?position: relative; ?display:none;}#bimg img{ ?width:1000px; ?height:1000px; ?position:absolute; ?top:0px; ?left:0px;}

function bigimg(){ ?var bbox = document.getElementById("box"); ?var bmove = document.getElementById("move"); ?var bbimg = document.getElementById("bimg"); ?var b_bimg = document.getElementById("b_bimg"); ?bbox.onmouseover = function(){//鼠标移动到box上显示大图片和选框 ???bbimg.style.display = "block"; ???bmove.style.display="block"; ?} ?bbox.onmouseout = function(){//鼠标移开box不显示大图片和选框 ???bbimg.style.display = "none"; ???bmove.style.display="none"; ?} ?bbox.onmousemove = function(e){//获取鼠标位置 ?????var e=e=e||window.event; ???var x = e.clientX;//鼠标相对于视口的位置 ???var y = e.clientY; ???var t = bbox.offsetTop;//box相对于视口的位置 ???var l = bbox.offsetLeft; ???var _left = x - l - bmove.offsetWidth/2;//计算move的位置left值 ???var _top = y - t -bmove.offsetHeight/2;//计算move的位置top值 ???if(_top<=0){//滑到box的最顶部 ?????_top = 0; ???}else if(_top>=bbox.offsetHeight-bmove.offsetHeight){//滑到box的最底部 ?????_top = bbox.offsetHeight-bmove.offsetHeight ;//bbox.offsetHeight-bmove.offsetHeight这是top的最大值 ???} ???if(_left<=0){//滑到box的最左边 ?????_left=0; ??} else if(_left>=bbox.offsetWidth-bmove.offsetWidth){//滑到box的最右边 ?????_left=bbox.offsetWidth-bmove.offsetWidth ;//bbox.offsetWidth-bmove.offsetWidth这是left的最大值 ?????} ???bmove.style.top = _top +"px";//设置move的位置 ???bmove.style.left = _left + "px"; ????var w =b_bimg.offsetWidth/bbox.offsetWidth;//计算移动的比例大图宽除以小图宽 ????var h =b_bimg.offsetHeight/bbox.offsetHeight; ???var b_bimg_top = _top*h;//计算大图的位置 ???var b_bimg_left = _left*w; ???b_bimg.style.top = -b_bimg_top + "px";//设置大图的位置信息 ???b_bimg.style.left = -b_bimg_left + "px"; ?} ???}bigimg()