<!DOCTYPE html>
<html lang="en" dir="ltr">
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>
    <div class="name">
      <div class="">
        <span>
          <img src="" alt="">
        </span>
      </div>
    </div>
  </body>
  <script type="text/javascript">
    function getNum(ele,box,num){
      var num = num ? num : 1;
      if(ele.parentNode == box){
        return num;// num = 4
      }else{
        num++;
        getNum(ele.parentNode,box,num);
      }
    }
    var a = document.getElementsByTagName("img")[0];
    var b = document.getElementsByTagName("body")[0];
    var c = getNum(a,b);
    console.log(c);
  </script>
</html>