放大镜大家在各大网站都能见到，下面小编给大家分享一段 ，代码是基于原生js实现的放大镜效果，代码简单易懂，非常不错，具有参考借鉴价值，感兴趣的朋友一起看看吧
这是我用原生js写的放大镜效果，与各种各样的框架技术相比，我喜欢使用原生的js，在这里，想和大家一起谈谈原生和框架技术的理解与个人喜好。
<!DOCTYPE HTML> <html> <head> <title>js放大镜效果</title> <meta http-equiv="content-type" content="text/html;charset=utf-8"/> <style> *{ margin:0px; padding:0px; border:none; list-style:none; } #box{ margin:80px auto; width: 352px; } #box p { width: 350px; height: 350px; border: 1px solid #ddd; margin-bottom: 5px; } #box p img { width:350px; height:350px; } #box h1 { width: 352px; height: 54px; overflow:hidden; position:relative; } #box h1 div { width:310px; height: 54px; margin:0px auto; position:relative; } #box h1 div ul { position:absolute; left: 0px; top: 0px; } #box h1 ul li { width: 62px; float: left; } #box h1 ul li img { width: 50px; height: 50px; padding: 1px; border: 1px solid #CECFCE; } #box h1 img.hoveredThumb{ border: 2px solid #e4393c; padding: 0; } /*中等大小的图片显示区域*/ p#medImgBox{ position: relative; } #jing{ position: absolute; left: 0; top: 0; width: 175px; height: 175px; border-radius:50%; background: #ffd; opacity: 0.7; display: none; } /*悬于图片/jing上方的专用于接收鼠标移动事件的 一个完全透明的层*/ #medImgBox #mian{ display: block; position: absolute; width: 100%; height: 100%; top: 0; left: 0; cursor: move; opacity: 0; } /** 大图显示区域 **/ #largeImgBox{ position:absolute; width: 175px; height: 175px; border-radius:50%; border: 1px solid #faa; top: 0px; left: 352px; overflow: hidden; display: none; } #largeImg{ display: none; position: absolute; } </style> </head> <body > <div> <p> <img src="https://www.jb51.net/images/product-s1-m.jpg" /> <span></span> <span></span> <span> <img/> </span> </p> <h1> <div> <ul> <li><img src="https://www.jb51.net/images\product-s1.jpg" /></li> <li><img src="https://www.jb51.net/images\product-s2.jpg" /></li> <li><img src="https://www.jb51.net/images\product-s3.jpg" /></li> <li><img src="https://www.jb51.net/images\product-s4.jpg" /></li> <li><img src="https://www.jb51.net/images\product-s1.jpg" /></li> </ul> </div> </h1> </div> <script> var imgList = document.querySelectorAll('#box ul li img'); for(var i=0; i<imgList.length; i++){ var img = imgList[i]; img.onmouseover = changeThumbImg; } function changeThumbImg(){ var previousHovered = document.querySelector('.hoveredThumb'); if(previousHovered==null){ this.className = 'hoveredThumb'; changeMediumImg(this.src); //修改中等图片的src }else if(previousHovered!=this){ previousHovered.removeAttribute('class'); this.className = 'hoveredThumb'; changeMediumImg(this.src); //修改中等图片的src } } function changeMediumImg(thumbSrc){ var dotIndex = thumbSrc.lastIndexOf('.'); var prefix = thumbSrc.substring(0, dotIndex); var suffix = thumbSrc.substring(dotIndex); var mediumSrc = prefix + '-m'+suffix; document.getElementById('mediumImg').src = mediumSrc; } /** 为放大镜jing添加鼠标移动事件 **/ document.querySelector('#mian').onmousemove = function(event){ var x = event.offsetX; //事件相对于事件源的偏移量 var y = event.offsetY; var jing = document.getElementById('jing'); var w = jing.offsetWidth; //jing的宽和高 var h = jing.offsetHeight; var left = x<w/2 ? 0 : (x-w/2); var top = y<h/2 ? 0 : (y-h/2); if(x>(w*2-w/2)){ left = w*2 - w; } if(y>(h*2-h/2)){ top = h*2 - h; } jing.style.left = left+'px'; jing.style.top = top+'px'; //修改大图的位置/ var largeImg = document.getElementById('largeImg'); largeImg.style.left = (-left*largeImg.width/350) + 'px'; largeImg.style.top = (-top*largeImg.height/350)+'px'; } document.querySelector('#mian').onmouseover = function(){ //显示jing var jing = document.getElementById('jing'); jing.style.display = 'block'; var largeImgBox = document.getElementById('largeImgBox'); largeImgBox.style.display = 'block'; //获取当前要显示的大图的src var src = document.querySelector('#mediumImg').src; var dotIndex = src.lastIndexOf('.'); var prefix = src.substring(0, dotIndex-2); var suffix = src.substring(dotIndex); src = prefix + '-l'+ suffix; var largeImg = document.getElementById('largeImg'); largeImg.src = src; largeImg.style.display='block'; } document.querySelector('#mian').onmouseout = function(){ //除去jing var jing = document.getElementById('jing'); jing.style.display = 'none'; //除去大图显示区 document.getElementById('largeImgBox').style.display = 'none'; } </script> </body> </html>