前台：
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Title</title><script type="text/javascript" src="/js/jquery-2.1.1.min.js"></script></head><style>.min{width: 350px;height: 350px;border: 1px solid black;float: left;position: relative;margin: 50px 0 0 30px;}.max{width: 350px;height: 350px;border: 1px solid black;float: left;display: none;overflow: hidden;position: relative;margin-left:30px ;}.max img{position: absolute;margin: 0 auto;}.fd{width: 153.125px;height: 153.125px;background-color: skyblue;opacity: 0.3;position: absolute;top: 0;left: 0;display: none;cursor: move;}</style><body><body><div class="min"><img src="D:\62526\Pictures\花火.jpg" width="350px" height="350px"/><div class="fd"></div></div><div class="max"><img src="D:\62526\Pictures\花火.jpg"/></div><script>var min = document.querySelector(".min");var max = document.querySelector(".max");var img = document.querySelector(".max img");var fd = document.querySelector(".fd");min.onmouseover = function(){//1.鼠标覆盖显示max和fdmax.style.display = "block";fd.style.display = "block";}// 离开时隐藏min.onmouseout = function(){max.style.display = "none";fd.style.display = "none";}// 2. fd的移动范围min.onmousemove = function(){//鼠标触摸的点var x = event.clientX-min.offsetLeft-fd.offsetWidth/2;var y = event.clientY-min.offsetTop-fd.offsetHeight/2;//最大移动距离var maxX = min.clientWidth-fd.offsetWidth;var maxY = min.clientHeight-fd.offsetHeight;//边界判断if (x <= 0) {x = 0;}else if (x >= maxX) {x = maxX;}if (y <= 0) {y = 0;}else if (y >= maxY) {y = maxY;}//fd的位置fd.style.left = x+'px';fd.style.top = y+'px';//fd/min = max/img//移动比例var moveX = x/maxX;var moveY = y/maxY;//移动//3. max的对应显示//对于大图而言,放大镜在小图上移动的比例相当于img在可显示区域上移动的比例//放大镜右移等于图片左移//也就是本质上为img-max 然而而需要负值,则*-1简化后为max-imgimg.style.left = moveX*(max.clientWidth - img.offsetWidth) + 'px';img.style.top = moveY*(max.clientHeight - img.offsetHeight) + 'px';}</script></body></html>
最终效果：
