JavaScript 解决切换图片问题

��代码：

            Document            .box1 {            width: 600px;            height: 500px;            border: 1px solid #333;            text-align: center;            margin: auto;        }        .box1 img {            width: 200px;            margin-top: 100px;            padding: 0px 30px;        }                        交换                        var img1 = document.querySelector('#box1img1');        var img2 = document.querySelector('#box1img2');        var btn = document.querySelector('#box1btn');        console.log(img1, img2, btn);        var flag = 1;        btn.onclick = function () {            if (flag) {                img1.src = 'https://blog.csdn.net/shan33__/article/img/img2.jpg';                img2.src = 'https://blog.csdn.net/shan33__/article/img/img1.jpg';                flag = 0;            } else {                img1.src = 'https://blog.csdn.net/shan33__/article/img/img1.jpg';                img2.src = 'https://blog.csdn.net/shan33__/article/img/img2.jpg';                flag = 1;            }        }    

效果图：