js realizes the magnifying glass effect of shopping website products

<div id="box">
    <div class="show">
        <img src="./images/1.jpg" alt="#">
        <div class="drag"></div>
    </div>
    <div class="magnify"></div>
    <ul>
        <li class="active"><img src="./images/1.small.jpg" alt="#"></li>
        <li><img src="./images/2.small.jpg" alt="#"></li>
    </ul>
</div>

<script type="text/javascript" src="./javascript/mgfyGlass.js"></script>

<script>
    const oBox = document.querySelector('#box');
    
    const imgArr = [
        {small: '1.small.jpg', normal: '1.jpg', big: '1.big.jpg'},
        {small: '2.small.jpg', normal: '2.jpg', big: '2.big.jpg'}
    ];
</script>

body,div,ul,li{
    margin: 0; padding: 0;
    list-style: none;
    font-size: 0;
}
img{
    display: block;
}
#box{
    width: 650px;
    position: relative;
    margin: 0 auto 0 240px;
}
#box .show{
    width: 600px;
    border: solid 2px hotpink;
    position: relative;
}
#box .show img{
    width: 100%;
}
#box .show .drag{
    position: absolute;
    width: 200px;
    height: 200px;
    background-color: #e0a8d7;
    opacity: .4;
    left: 0;
    top: 0;
    display: none;
}
#box .magnify{
    width: 800px;
    height: 800px;
    border: solid 2px #7d777b;
    position: absolute;
    left: 100%;
    top: 0;
    background: url("../images/1.big.jpg") no-repeat 0 0 / 2400px;
    display: none;
}
#box ul{
    width: 100%;
    height: 150px;
    margin-top: 20px;
}
#box ul::after{
    content: '';
    display: block;
    clear: both;
}
#box ul li{
    height: 100%;
    float: left;
    margin: 0 8px;
    border: solid 2px #fff;
}
#box ul li.active{
    border-color: hotpink;
}
#box ul li img{
    height: 100%;
}

class MgnGlass {
    constructor(ele, array) {
        this.ele = ele;
        this.array = array;

        this.show = ele.querySelector('.show');
        this.showImg = this.show.querySelector('img');
        this.drag = ele.querySelector('.drag');
        this.magnify = ele.querySelector('.magnify');
        this.oUl = ele.querySelector('ul');
        this.oUlis = ele.querySelectorAll('ul li');
    }

 // Define a method to call all methods defined later // Entry function init() {
        this.setMouse();
        this.setPosition();
        this.setTab();
    }

    //Mouse movement in and out setMouse() {
     //Mouse over, show the image area, and display the cover layer and magnifying glass this.show.addEventListener('mouseover', () => {
            this.drag.style.display = 'block';
            this.magnify.style.display = 'block';
        });
        //Mouse out, show the image area, hide the cover layer and magnifying glass this.show.addEventListener('mouseout', () => {
            this.drag.style.display = 'none';
            this.magnify.style.display = 'none';
        });
    }

 // Set the positioning effect // When the mouse moves in the image area // 1. Let the cover layer follow the mouse movement---similar to the previous mouse drag effect setPosition() {
        this.show.addEventListener('mousemove', (e) => {
            e = e || event;
            // 1. Position the cover layer // Calculate the coordinate position of the upper left corner of the cover layer by the mouse position let x = e.clientX - this.ele.offsetLeft - this.ele.clientLeft - this.drag.clientWidth / 2;
            let y = e.clientY - this.ele.offsetTop - this.ele.clientTop - this.drag.clientHeight / 2;

   // 2, set the boundary value // minimum is 0 maximum is parent div width and height - cover layer width and height if (x < 0) {
                x = 0;
            }
            else if (x > (this.show.clientWidth - this.drag.clientWidth)){
                x = this.show.clientWidth - this.drag.clientWidth;
            }
            if (y < 0){
                y = 0;
            }
            else if (y > (this.show.clientHeight - this.drag.clientHeight)){
                y = this.show.clientHeight - this.drag.clientHeight;
            }

   // 3, position the value to the cover layer this.drag.style.left = x + 'px';
            this.drag.style.top = y + 'px';

   // 4. The background image of the magnifying glass on the right needs to move together // Add positioning to the background image // The image on the left is stationary, and the cover layer moves Cover layer moves 100 100
            // On the right is the magnifying glass, which is not moving, and the background image is moving. Background image is moving -100 -100
            // When moving, the positioning must be set according to the proportion // Background image positioning = background image size * cover layer positioning / image size // Calculate the background image positioning value by the proportion of the cover layer movement let backX = 2400 * x / 600;
            let backY = 2400 * y / 600;

   // Position the background image // Position the background image this.magnify.style.backgroundPosition = `-${backX}px -${backY}px`;
        })
    }

 // Switching effect // 1. Add style to the label that the mouse is currently over // Remove styles from all labels and add style to the label that is currently clicked/passed over setTab() {
        this.oUlis.forEach((item, key) => {
            item.addEventListener('mouseover', () => {
             // 1, clear the style of all li tags this.oUlis.forEach((item2) => {
                    item2.className = '';
                });
                // 2, add style to the current tag item.className = 'active';

    // 3, set the image // The index subscript key of the current label is the index subscript of the image to be displayed in the corresponding image array // 1, set the path for the image label // Get the corresponding image name through array, index, and image attributes // label.src = assignment or label.setAttribute('src', attribute value) this.showImg.setAttribute('src', `./images/${this.array[key].normal}`);
                // 2. Set the path of the background image for the magnifying glass area. // All settings about the background image must be rewritten this.magnify.style.background = `url('./images/${this.array[key].big}') no-repeat 0 0 / 2400px`;
            })
        })
    }
}

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width,initial-scale=1.0">
    <title>Magnifying Glass</title>
    <link rel="stylesheet" type="text/css" href="./css/mgfyGlass.css" >
</head>
<body>
    <div id="box">
        <div class="show">
            <img src="./images/1.jpg" alt="#">
            <div class="drag"></div>
        </div>
        <div class="magnify"></div>
        <ul>
            <li class="active"><img src="./images/1.small.jpg" alt="#"></li>
            <li><img src="./images/2.small.jpg" alt="#"></li>
        </ul>
    </div>

    <script type="text/javascript" src="./javascript/mgfyGlass.js"></script>

    <script>
        const oBox = document.querySelector('#box');
        
        const imgArr = [
            {small: '1.small.jpg', normal: '1.jpg', big: '1.big.jpg'},
            {small: '2.small.jpg', normal: '2.jpg', big: '2.big.jpg'}
        ];
        
        const mgnGlass = new MgnGlass(oBox, imgArr);
    
        mgnGlass.init();
    
    
    </script>
</body>
</html>