怎样保持div中的子元素的长宽比例展示

<!DOCTYPE html>
<html>
 <head> 
  <meta charset="utf-8" /> 
  <title>菜鸟教程(runoob.com)</title> 
  <style>
        .container {
        height: 0;
  padding: 20%;
  position: relative;
        }
        .container div{
            border: 2px solid #dddddd;
  height: 100%;
  left: 0;
  position: absolute;
  top: 0;
  width: 100%;
        }
    </style> 
 </head> 
 <body> 
  <div class="container"> 
   <div class="">
     aaaa 
   </div> 
  </div>  
 </body>
</html>

菜鸟教程(runoob.com)

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原文地址：https://www.cnblogs.com/shangguancn/p/13427741.html