请问以下实例中对json数据处理的部分怎么理解？

Question

<script>

  $(document).ready(function() {

    $("#getMessage").on("click", function() {

      $.getJSON("/json/cats.json", function(json) {

        var html = "";

        json.map(function(obj) {

        

          var keys = Object.keys(obj)；

          html += "<div class = 'cat'>";

          keys.map(function(key) {

            html += "<b>" + key + "</b>: " + obj[key] + "<br>";

          });

          

          html += "</div><br>";

        });    

        

        $(".message").html(html);

      });

    });

  });

</script>

<div class="container-fluid">

  <div class = "row text-center">

    <h2>Cat Photo Finder</h2>

  </div>

  <div class = "row text-center">

    <div class = "col-xs-12 well message">

      The message will go here

   </div>

  </div>

  <div class = "row text-center">

    <div class = "col-xs-12">

      <button id = "getMessage" class = "btn btn-primary">

        Get Message

      </button>

    </div>

  </div>

</div>