<!DOCTYPE html> <html>

<head>
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
  <div id="json" data-json="%7B%22key%22%3A%22value%22%2C%22test%22%3A%5B%22one%22%2C%22two%22%2C%22three%22%5D%7D"></div>
  <div id="test"></div>
  <script>
    (function(){
      var testel = document.getElementById('test');
      testel.innerHTML='complete';
      var datael = document.getElementById('json');
      var data;
      data=JSON.parse(decodeURIComponent(datael.dataset.json));
      if(!!data){
        testel.innerHTML+=data.test
      }
      var evt = document.createEvent("Event")
      evt.initEvent('test', true, true);
      document.dispatchEvent(evt);
    })()
  </script>
</body>

</html>