Need help on json to html convert

JavaScript
1

question link

<script>
  document.addEventListener('DOMContentLoaded',function(){
    document.getElementById('getMessage').onclick=function(){
      req=new XMLHttpRequest();
      req.open("GET",'/json/cats.json',true);
      req.send();
      req.onload=function(){
        json=JSON.parse(req.responseText);
        var html = "";
        // Add your code below this line
        json.forEach(function(val){
          var keys=Object.keys(val);
          html+="<div class='cat'>";
          keys.forEach(function(key){
            html+="<strong>"+key+"</strong><br>";
          });
          html+="</div>";
        });
                // Add your code above this line
        document.getElementsByClassName('message')[0].innerHTML=html;
      };
    };
  });
</script>
<style>
  body {
    text-align: center;
    font-family: "Helvetica", sans-serif;
  }
  h1 {
    font-size: 2em;
    font-weight: bold;
  }
  .box {
    border-radius: 5px;
    background-color: #eee;
    padding: 20px 5px;
  }
  button {
    color: white;
    background-color: #4791d0;
    border-radius: 5px;
    border: 1px solid #4791d0;
    padding: 5px 10px 8px 10px;
  }
  button:hover {
    background-color: #0F5897;
    border: 1px solid #0F5897;
  }
</style>
<h1>Cat Photo Finder</h1> 
<p class="message box">
  The message will go here
</p>
<p>
  <button id="getMessage">
    Get Message
  </button>
</p>

it says an error

Your code should store the data in the html variable

i am not getting whats the error

2

“…adding HTML to the variable that wraps the key names in strong tags, followed by the value.”