原理： 其实所谓的放大就是准备两张一样的图片，除大小不一样。鼠标移动到不同位置，将会显示大图片对应的图片内容。
完整代码：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>放大镜效果</title> </head> <body> <div> <div> <img src="https://www.jb51.net/small.jpg"/> <span> <span> </div> <div> <img src="https://www.jb51.net/large.jpg"> </div> </div> <script type="text/javascript"> var filter = document.getElementById('filter'); var smallImg = document.getElementById('smallImg'); var bigImg = document.getElementById('bigImg'); var wrap = document.getElementById('wrap'); var largeImgs = bigImg.getElementsByTagName('img')[0]; smallImg.onmouseover = function(){ bigImg.style.display = "inline-block"; filter.style.display = "inline-block"; } smallImg.onmousemove = function(event){ var event = event || window.event; var mouseleft = event.clientX - wrap.offsetLeft; var mousetop = event.clientY - wrap.offsetTop; var left = mouseleft<smallImg.offsetWidth/4?0:mouseleft>smallImg.offsetWidth*3/4?smallImg.offsetWidth/2:(mouseleft - filter.offsetWidth/2); var top = mousetop<smallImg.offsetHeight/4?0:mousetop>smallImg.offsetHeight*3/4?smallImg.offsetHeight/2:(mousetop - filter.offsetWidth/2); filter.style.left = left + "px"; filter.style.top = top +"px"; largeImgs.style.left = "-" + left*bigImg.offsetWidth/smallImg.offsetWidth + "px"; largeImgs.style.top = "-" + top*bigImg.offsetHeight/smallImg.offsetHeight + "px"; } smallImg.onmouseout = function(){ bigImg.style.display = "none"; filter.style.display = "none"; } </script> </body> </html>
运行效果：
更多关于JavaScript相关内容感兴趣的读者可查看本站专题：《JavaScript图片操作技巧大全》、《JavaScript图形绘制技巧总结》、《JavaScript页面元素操作技巧总结》、《JavaScript事件相关操作与技巧大全》、《JavaScript数据结构与算法技巧总结》及《JavaScript数学运算用法总结》