screenshots.gif

<!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>
        *{
            margin:0;
            padding:0;
        }

        #pic{width: 100px;
            position:fixed;
        }

    </style>
</head>
<body>

    <img src="2.gif" alt="蝴蝶" id="pic">

    <script>
        //通过 鼠标移动事件给 图片添加 left 和 top 的值
        //获取元素
        var pic = document.getElementById("pic");

        //给整个文档添加鼠标移动事件

        document.onmousemove = function(e){
            e = e || window.event;
            //给元素的css 属性赋值
            pic.style.left = e.clientX+"px";
            pic.style.top = e.clientY+"px";
        };


    </script>
    
</body>
</html>