注意：里边的两张图片(一大一小)可以自己添加，JQ采用jquery-1.11.3.js版，也可自行调换。
HTML代码：
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>jQuery放大镜</title>
<link rel="stylesheet" href="css/reset.min.css"/>
<link rel="stylesheet" href="css/index.css"/>
</head>
<body>
<div class="wrapper">
<div class="small">
<img src="img/1.jpg" alt=""/>
<div class="mask"></div>
</div>
<div class="big">
<img src="img/2.jpg" alt=""/>
</div>
</div>
<script src="js/jquery-1.11.3.js"></script>
<script src="js/index.js"></script>
</body>
</html>
CSS代码：
@charset "UTF-8";
.wrapper{
width: 800px;
margin: 50px auto;
position: relative;
}
.wrapper .small{
position: absolute;
top:;
left:;
width: 350px;
height: 350px;
border: 1px solid #000000;
box-shadow: 3px 3px 5px #aaa;
}
.wrapper .small img{
width: 100%;
height: 100%;
}
.wrapper .small .mask{
display: none;
position: absolute;
top:;
left:;
width: 150px;
height: 150px;
background-color: #000000;
opacity: .4;
cursor: move;
} .wrapper .big{
display: none;
position: absolute;
overflow: hidden;
top:;
left: 355px;
border: 1px solid #000000;
box-shadow: 3px 3px 5px #aaa;
}
.wrapper .big img{
position: absolute;
width: 800px;
height: 800px;
top:;
left:;
}
reset.min.css文件：
body,h1,h2,h3,h4,h5,h6,hr,p,blockquote,dl,dt,dd,ul,ol,li,button,input,textarea,th,td{margin:;padding:}body{font-size:12px;font-style:normal;font-family:"\5FAE\8F6F\96C5\9ED1",Helvetica,sans-serif}small{font-size:12px}h1{font-size:18px}h2{font-size:16px}h3{font-size:14px}h4,h5,h6{font-size:100%}ul,ol{list-style:none}a{text-decoration:none;background-color:transparent}a:hover,a:active{outline-width:;text-decoration:none}table{border-collapse:collapse;border-spacing:}hr{border:;height:1px}img{border-style:none}img:not([src]){display:none}svg:not(:root){overflow:hidden}html{-webkit-touch-callout:none;-webkit-text-size-adjust:100%}input,textarea,button,a{-webkit-tap-highlight-color:rgba(0,0,0,0)}article,aside,details,figcaption,figure,footer,header,main,menu,nav,section,summary{display:block}audio,canvas,progress,video{display:inline-block}audio:not([controls]),video:not([controls]){display:none;height:}progress{vertical-align:baseline}mark{background-color:#ff0;color:#000}sub,sup{position:relative;font-size:75%;line-height:;vertical-align:baseline}sub{bottom:-0.25em}sup{top:-0.5em}button,input,select,textarea{font-size:100%;outline:}button,input{overflow:visible}button,select{text-transform:none}textarea{overflow:auto}button,html [type="button"],[type="reset"],[type="submit"]{-webkit-appearance:button}button::-moz-focus-inner,[type="button"]::-moz-focus-inner,[type="reset"]::-moz-focus-inner,[type="submit"]::-moz-focus-inner{border-style:none;padding:}button:-moz-focusring,[type="button"]:-moz-focusring,[type="reset"]:-moz-focusring,[type="submit"]:-moz-focusring{outline:1px dotted ButtonText}[type="checkbox"],[type="radio"]{box-sizing:border-box;padding:}[type="number"]::-webkit-inner-spin-button,[type="number"]::-webkit-outer-spin-button{height:auto}[type="search"]{-webkit-appearance:textfield;outline-offset:-2px}[type="search"]::-webkit-search-cancel-button,[type="search"]::-webkit-search-decoration{-webkit-appearance:none}::-webkit-input-placeholder{color:inherit;opacity:.54}::-webkit-file-upload-button{-webkit-appearance:button;font:inherit}.clear:after{display:block;height:;content:"";clear:both}
JS代码：
/**
* Created by 35107 on 2017/5/8.
*/
$(function () {
var smallL, smallT, minL = 0, minT = 0, maxL, maxT;
var $wrapper = $('.wrapper'),
$small = $wrapper.children('.small'),
$mask = $small.children('.mask'),
$big = $wrapper.children('.big'),
$curImg = $small.children('img'),
$bigImg = $big.children('img');
var multiple = 2 / 3, n = null,
maskW = $curImg.width() * multiple,
maskH = $curImg.height() * multiple,
bigW = $bigImg.width() * multiple,
bigH = $bigImg.width() * multiple;
$mask.css({width: maskW, height: maskH});
$big.css({width: bigW, height: bigH}); $small.on({
mouseenter: function (e) {
$mask.css('display', 'block');
$big.css('display', 'block');
setPos(e);
},
mousemove: function (e) {
setPos(e);
},
mouseleave: function () {
$mask.css('display', 'none');
$big.css('display', 'none');
}
}); function setPos(e) {
if (!smallL) {
smallL = $small.offset().left;
smallT = $small.offset().top;
maxL = $small.innerWidth() - maskW;
maxT = $small.innerHeight() - maskW;
n = ($bigImg.width() - bigW ) / maxL;
} var curL = e.clientX - smallL - maskW / 2,
curT = e.clientY - smallT - maskH / 2;
curL = curL < minL ? minL : (curL > maxL ? maxL : curL);
curT = curT < minT ? minT : (curT > maxT ? maxT : curT);
$mask.css({left: curL, top: curT});
$bigImg.css({left: -curL * n, top: -curT * n})
} function calculatedWidth() { }
});