span元素宽高设置问题，为何父级设置相对定位，span设置绝对定位后宽高生效了？

<!DOCTYPE html>
<html>
   <head>
       <meta charset="utf-8">
       <title></title>
       <style>
           .box{
               width: 200px;
               height: 200px;
               border: 1px solid black;
                position: relative;
           }
           .box span{
               width: 50px;
               height: 50px;
               background-color: yellow;
               position: absolute;
               right: -10px;
               top: -10px;
           }
       </style>
   </head>
   <body>
       <div class="box">
           <div class="item"></div>
            <span></span>
       </div>
   </body>
</html>

浮世绘3145722

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span元素宽高设置问题，为何父级设置相对定位，span设置绝对定位后宽高生效了？

2回答