我想把JSON数据添加到浏览器cookie中，然后在DIV中列出添加的JSON数据。但是，我在控制台中得到一个错误。这可能是什么原因，我哪里出错了？

$(document).ready(function() {
   var obj = [{
     "file-postSender_revize1.png": {
       "asrs": "gi",
       "name": "postSender_revize1.png",
       "life": "48",
       "type": "parcel"
     }
   },{
     "file-postSender_revize2.png": {
       "asrs": "gi",
       "name": "postSender_revize2.png",
       "life": "24",
       "type": "parcel"
     }
   }];

   document.cookie = "uploadFiles=" + obj;
   var str = JSON.stringify(getCookie('uploadFiles'));
   var json = JSON.parse(str);
   for (var i = 0; i < json.length; i++) {
     document.getElementById('fileList').innerHTML += json[i].name;
   }

 });

 function getCookie(name) {
   const value = `; ${document.cookie}`;
   const parts = value.split(`; ${name}=`);
   if (parts.length === 2) return parts.pop().split(';').shift();
 }

控制台：

"jQuery.Deferred exception: \"undefined\" is not valid JSON", "SyntaxError: \"undefined\" is not valid JSON
    at JSON.parse (<anonymous>)
    at HTMLDocument.<anonymous> (https://fiddle.jshell.net/_display/?editor_console=true:124:20)
    at mightThrow (https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.js:3557:29)
    at process (https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.js:3625:12)", undefined