层级和定位

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        div {
            margin-top: 20px;
            width: 200px;
            height: 200px;
            background-color: red;
            position: absolute;
            top: 100px;
            left: 10px;
            z-index: 1;
        }
        img {
            position: absolute;
            top: 100px;
            left: 10px;
        }
    </style>
</head>
<body>
    <button>动!!!</button>
    <div></div>
    ![](image/mm.png)

    <script>
        //需求:点击按钮,让盒子和图片同事移开,并且,图片压住盒子.
        var btn = document.getElementsByTagName("button")[0];
        var div = document.getElementsByTagName("div")[0];
        var img = document.getElementsByTagName("img")[0];

        //绑定事件
        btn.onclick = function () {
            div.style.top = "300px";
            div.style.left = "300px";

            img.style.top = "300px";
            img.style.left = "300px";
            img.style.zIndex = "2";
        }

    </script>

</body>
</html>

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