| 本文实例为大家分享了JavaScript实现简易放大镜的具体代码，供大家参考，具体内容如下 
完整代码： <!DOCTYPE html><html><head> <meta charset="UTF-8"> <title>ES5放大镜</title> <style> .box { width: 170px; height: 180px; margin: 100px 200px; border: 1px solid #ccc; position: relative; } .small { position: relative; } .big { width: 300px; height: 320px; position: absolute; top: 30px; left: 220px; overflow: hidden; border: 1px solid #ccc; display: none; } .mask { width: 100px; height: 100px; background: rgba(255,255,0,0.3); position: absolute; top: 0; left: 0; cursor: move; display: none; } .big img{ position: absolute; left: 0; top: 0; } </style></head><body> <div class="box" id="box"> <div class="small"> <img src="img/shirt_1.jpg" alt="picture"/> <div class="mask"></div> </div> <div class="big"> <img src="img/shirt_1_big.jpg" alt="picture"/> </div> </div></body><script> var box = document.getElementById('box'); var small = box.children[0];//放小图的盒子 var big = box.children[1];//放大图的盒子 var mask = small.children[1];//半透明鼠标移动跟随盒子 var bigImage = big.children[0];//大图片 small.onmouseover = function(event){ big.style.display = 'block'; mask.style.display = 'block'; } small.onmouseout = function(){ big.style.display = 'none'; mask.style.display = 'none'; } //移动事件，注意mask的定位相对的是samll small.onmousemove = function(event){ var event = event || window.event;//事件对象 // console.log(this.offsetLeft);//0,注意offsetLeft返回距离是一个带有定位的父级的左侧距离 var x = event.clientX-this.offsetParent.offsetLeft-mask.offsetWidth/2;//此处不能用small的offsetLeft,用obj的offsetLeft var y = event.clientY-this.offsetParent.offsetTop-mask.offsetHeight/2; //限制半透明盒子出界 if(x < 0){ x = 0; }else if(x > small.offsetWidth - mask.offsetWidth){ x = small.offsetWidth - mask.offsetWidth; } if( y < 0){ y = 0; }else if( y > small.offsetHeight - mask.offsetHeight){ y = small.offsetHeight - mask.offsetHeight; } mask.style.left = x + "px"; mask.style.top = y +"px"; //大图片放大 bigImage.style.left = -x*big.offsetWidth/small.offsetWidth + 'px'; bigImage.style.top = -y*big.offsetHeight/small.offsetHeight + 'px'; //big.offsetWidth/small.offsetWidth是放大倍数 //因为小图鼠标下移，大图上移，故用负数 }</script></html>图片： 
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