```	    <!DOCTYPE html>
    <html>
        <head>
            <meta charset=utf-8>
            <style type="text/css">
                .box {
                    width: 100px;
                    height: 100px;
                    border: solid 1px black;
                    //子绝父相
                    
                    position:relative;
                    
                }
                .btn{
                    width: 20px;
                    height: 20px;
                    background-color: red;
                   //设定居中对齐
                    text-align:center;
					//设定btn位置
                    position:absolute;
                    top:-10px;
                    right:-10px;
                }
            </style>
        </head>
        <body>
    
            <div class='box'>
                <div class='btn'>X</div>
            </div>
    
            <script type="text/javascript">
                var btn = document.querySelector('.btn');
                var box = document.querySelector('.box');
                btn.onclick = function(){
                    // 点击btn后box隐藏
                    box.style.display='none';
                    
                }
            </script>
        </body>
    </html>