鼠标移动图片放大出现在旁边

手机官网里这种鼠标移动或者悬停在图片上，旁边就会有一个放大的图片，这种请问怎么做呀


<!DOCTYPE html>
<html>
 
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
 
        .box {
            width: 350px;
            height: 350px;
            margin: 100px;
            border: 1px solid #ccc;
            position: relative;
        }
 
        .big {
            width: 400px;
            height: 400px;
            position: absolute;
            top: 0;
            left: 360px;
            border: 1px solid #ccc;
            overflow: hidden;
            display: none;
        }
 
        .big img {
            position: absolute;
            width: 800px;
        }
 
        .mask {
            width: 175px;
            height: 175px;
            background: rgba(255, 255, 0, 0.4);
            position: absolute;
            top: 0px;
            left: 0px;
            cursor: move;
            display: none;
        }
 
        .small {
            position: relative;
        }
    </style>
</head>
 
<body>
    <div class="box" id="box">
        <div class="small">
            <img src="https://img2.baidu.com/it/u=3104870425,3464488586&fm=253&app=120&size=w931&n=0&f=JPEG&fmt=auto?sec=1663866000&t=eb2be26093cef37a2e8b1b177909fada" width="350" alt="" />
            <div class="mask"></div>
        </div>
        <div class="big">
            <img src="https://img2.baidu.com/it/u=3104870425,3464488586&fm=253&app=120&size=w931&n=0&f=JPEG&fmt=auto?sec=1663866000&t=eb2be26093cef37a2e8b1b177909fada" alt="" />
        </div>
    </div>
    <script>
        function my$(id) {
            return document.getElementById(id)
        }
        var box = my$('box');
        var smallBox = box.children[0];
        var bigBox = box.children[1];
        console.log(bigBox.style.width);
        var smallImage = smallBox.children[0];
        var mask = smallBox.children[1];
        var bigImage = bigBox.children[0];
        console.log(bigImage.style.width);
 
 
        // 1 鼠标经过的时候 显示 mask和bigBox ， 当鼠标离开box的时候隐藏mask和bigBox
        // mouseenter   mouseleave     不会触发事件冒泡
        // mouseover   mouseout        会触发事件冒泡
        box.onmouseenter = function () {
            // 显示 mask和bigBox 
            mask.style.display = 'block';
            bigBox.style.display = 'block'
        }
 
        box.onmouseleave = function () {
            mask.style.display = 'none';
            bigBox.style.display = 'none';
        }
 
        // 2 当鼠标在盒子中移动的时候，让mask和鼠标一起移动
        box.onmousemove = function (e) {
            e = e || window.event;
            // 获取鼠标在盒子中的位置，就是mask的坐标
            var maskX = e.pageX - box.offsetLeft;
            var maskY = e.pageY - box.offsetTop;
 
            // 让鼠标出现在mask的中心点
            maskX = maskX - mask.offsetWidth / 2;
            maskY = maskY - mask.offsetHeight / 2;
 
            // 把mask限制到box中
            maskX = maskX < 0 ? 0 : maskX;
            maskY = maskY < 0 ? 0 : maskY;
 
            maskX = maskX > box.offsetWidth - mask.offsetWidth ? box.offsetWidth - mask.offsetWidth : maskX;
            maskY = maskY > box.offsetHeight - mask.offsetHeight ? box.offsetHeight - mask.offsetHeight : maskY;
 
 
            mask.style.left = maskX + 'px';
            mask.style.top = maskY + 'px';
            // 3 当mask移动的时候，让大图片移动
            // 求 大图片移动的距离
 
            // mask移动的距离 / mask最大能够移动的距离  = 大图片移动的距离 / 大图片最大能够移动的距离
 
            // mask最大能够移动的距离
            var maskMax = box.offsetWidth - mask.offsetWidth;
            // 大图片最大能够移动的距离
            var bigImageMax = bigImage.offsetWidth - bigBox.offsetWidth;
 
            var bigImageX = maskX * bigImageMax / maskMax;
            var bigImageY = maskY * bigImageMax / maskMax;
 
            bigImage.style.left = -bigImageX + 'px';
            bigImage.style.top = -bigImageY + 'px';
        }
    </script>
</body>
 
</html>


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