JavaScript 图片放大预览效果

代码实现：

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .preview-img {
            position: relative;
            height: 398px;
        }
        
        .mask {
            display: none;
            position: absolute;
            top: 0;
            left: 0;
             300px;
            height: 300px;
            background-color: skyblue;
            opacity: .4;
            border: 1px solid #ccc;
            cursor: move;
        }
        
        .big {
            overflow: hidden;
            display: none;
            position: absolute;
            top: 0;
            left: 410px;
             500px;
            height: 500px;
            background-color: pink;
            z-index: 99;
            border: 1px solid #ccc;
        }
        
        .big img {
            position: absolute;
            top: 0;
            left: 0;
        }
    </style>
</head>

<body>
    <script>
        window.addEventListener('load', function() {
            var preview_img = document.querySelector('.preview-img');
            var mask = document.querySelector('.mask');
            var big = document.querySelector('.big');
            // 显示与隐藏
            preview_img.addEventListener('mouseover', function() {
                mask.style.display = 'block';
                big.style.display = 'block';
            });
            preview_img.addEventListener('mouseout', function() {
                mask.style.display = 'none';
                big.style.display = 'none';
            });
            // 盒子跟随鼠标移动
            preview_img.addEventListener('mousemove', function(e) {
                var x = e.pageX - this.offsetLeft;
                var y = e.pageY - this.offsetTop;
                var maskX = x - mask.offsetWidth / 2;
                var maskY = y - mask.offsetHeight / 2;
                var maskMax = preview_img.offsetHeight - mask.offsetHeight;
                if (maskX <= 0) {
                    maskX = 0;
                } else if (maskX >= maskMax) {
                    maskX = maskMax;
                }
                if (maskY <= 0) {
                    maskY = 0;
                } else if (maskY >= maskMax) {
                    maskY = maskMax;
                }
                mask.style.left = maskX + 'px';
                mask.style.top = maskY + 'px';

                // 大图，根据比例计算坐标
                var bigImg = document.querySelector('.bigImg');
                var bigMax = bigImg.offsetWidth - big.offsetWidth;
                var bigX = bigMax * maskX / maskMax;
                var bigY = bigMax * maskY / maskMax;
                bigImg.style.left = -bigX + 'px';
                bigImg.style.top = -bigY + 'px';
            });
        });
    </script>
    <div class="preview-img">
        <img src="https://s1.ax1x.com/2020/10/12/027yRg.jpg" alt="">
        <div class="mask"></div>
        <div class="big">
            <img src="https://s1.ax1x.com/2020/10/12/0276zQ.jpg" alt="" class="bigImg">
        </div>
    </div>
</body>

</html>
JavaScript 图片放大预览效果

代码实现：

实现效果：
