原生JS实现简单放大镜效果

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我是靠谱客的博主繁荣戒指，最近开发中收集的这篇文章主要介绍原生JS实现简单放大镜效果，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

本文实例为大家分享了原生JS实现放大镜效果的具体代码，供大家参考，具体内容如下

<html>

 <head>
 <meta charset="UTF-8">
 <title></title>
 <style type="text/css">
  * {
  margin: 0;
  padding: 0;
  }
  img{
  vertical-align: top;
  }
  .fdj {
  width: 350px;
  height: 350px;
  position: relative;
  margin: 100px auto;
  border: 1px solid gainsboro;
  }
  .small {
  position: relative;
  }
  .small img {
  width: 350px;
  }
  .mask {
  width: 100px;
  height: 100px;
  background: rgba(255, 255, 0, 0.4);
  position: absolute;
  left: 0;
  top: 0;
  cursor: move;
  display: none;
  }
  .big {
  position: absolute;
  top: 0;
  left: 360px;
  width: 500px;
  height: 500px;
  border: 1px solid gainsboro;
  overflow: hidden;
  display: none;
  }
  .big img{
  position: absolute;
  left: 0;
  top: 0;
  }
 </style>
 </head>

 <body>
 <div class="fdj">
  <div class="small">
  <img src="http://cdn.attach.qdfuns.com/notes/pics/201702/08/162503mw0fawb5b02va22i.jpg" />
  <div class="mask"></div>
  </div>
  <div class="big">
  <img src="http://cdn.attach.qdfuns.com/notes/pics/201702/08/162503mw0fawb5b02va22i.jpg" />
  </div>
 </div>
 </body>
 <script type="text/javascript">
 var fdj = document.querySelector('.fdj') // 获得最大的盒子
 var small = document.querySelector('.small'); //获取小图片盒子
 var big = document.querySelector('.big'); //获取大图片盒子
 var bigs = big.children[0] //大图片 
 var smalls = small.children[0] //小图片
 var mask = small.children[1]; //遮罩

 //鼠标移入小图片盒子
 small.onmouseover = function() {
  //鼠标移入图片盒子将遮罩与大图片显示
  mask.style.display = 'block';
  big.style.display = ' block';
 };

 //鼠标移出小图片盒子
 small.onmouseout = function() {
  //鼠标移出小图片盒子将遮罩与大图片隐藏
  mask.style.display = 'none';
  big.style.display = 'none';
 };

 var x=0;
 var y=0;
 //鼠标在小图片上移动时
 small.onmousemove = function(ev) {
  var ev = event || window.event;
 //让鼠标在遮罩正中
  //鼠标X坐标与Y坐标
  x = ev.clientX -this.offsetParent.offsetLeft- mask.offsetWidth / 2 ; 
  y = ev.clientY -this.offsetParent.offsetTop- mask.offsetHeight / 2 ;
  //将遮罩限制在小图片盒子中

  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';

  //大图与小图的比例

  /*var scalX = bigs.offsetWidth/small.offsetWidth;
  var scalY = bigs.offsetHeight/small.offsetHeight;*/

  var scalX = x/(small.offsetWidth-mask.offsetWidth);
  var scalY = y/(small.offsetHeight-mask.offsetHeight);

  bigs.style.left = -(x*scalX)+'px';
  bigs.style.top = -(y*scalY)+'px';

 };

 </script>

</html>

效果图：（演示）