js实现商城放大镜效果

css部分

* {
            margin: 0;
            padding: 0;
        }

        /* img {
            vertical-align: top;
            } */

        .box {
            width: 350px;
            height: 350px;
            position: relative;
            border: 1px solid black;
            margin: 150px 0 0 300px;
        }

        .big {
            width: 450px;
            height: 450px;
            position: absolute;
            border: 1px solid black;
            left: 400px;
            top: 0;
            display: none;
            overflow: hidden;
        }

        .small {
            position: relative;
        }

        .mask {
            width: 100px;
            height: 100px;
            background-color: rgba(255, 255, 0, 0.4);
            position: absolute;
            left: 0;
            top: 0;
            cursor: move;
            display: none;
        }

        .big img {
            position: absolute;
            left: 0;
            top: 0;
        }

HTML部分

 <div class="box" id="oBox">
        <div class="small" id="oSmall">
            <img src="./images/001.jpg" alt="">
            <div class="mask" id="oMask"></div>
        </div>
        <div class="big" id="oBig">
            <img src="./images/0001.jpg" alt="">
        </div>
    </div>

js部分

//第一步获取节点
    let box = document.getElementById('oBox');
    let small = box.children[0]; //获取盒子的第一个子节点samll
    let big = box.children[1]; //获取盒子的第二个子节点big
    let mask = small.children[1]; //获取小盒子里的遮罩
    let bigImg = big.children[0]; //获取大盒子里的图片


    //鼠标进入small 遮罩(mask)大盒子(big)display:block
    small.onmouseover = function() {
        mask.style.display = 'block';
        big.style.display = 'block';

    };

    //鼠标离开small 遮罩(mask)大盒子(big)display:none
    small.onmouseout = function() {
        mask.style.display = 'none';
        big.style.display = 'none';
    };

    let x = 0;
    let y = 0;


    small.onmousemove = function(even) {
        var even = even || window.event;

        // 获取鼠标在small里的坐标
        let x = even.clientX - this.offsetParent.offsetLeft - mask.offsetWidth / 2;
        let y = even.clientY - this.offsetParent.offsetTop - mask.offsetHeight / 2;


        // 限制住鼠标的坐标导致遮罩的位置越界
        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';
        //注意大图片的方向
        bigImg.style.top = -y * big.offsetHeight / small.offsetHeight + 'px';
        bigImg.style.left = -x * big.offsetWidth / small.offsetWidth + 'px';
    };