testing.html

<!DOCTYPE html>
<html>
  <head>
    <title>Testing</title>
  </head>
  <body>
    <form id="basicForm" onsubmit="formSubmission(event)">
      <input type="text" name="name">
      <br>
      <input type="submit" value="Submit">
    </form>
  </body>
</html>

<script>
  function formSubmission(event) {
    event.preventDefault();
    loadHtmlFile("success.html");
  }

  function loadHtmlFile(url){
    var xhr = createCORSRequest('GET', url);
    if (!xhr) {
      throw new Error('CORS not supported');
    }

    // Response handlers.
    xhr.onload = function() {
      var text = xhr.responseText;
      parent.window.frames['formFrame'].src="data:text/html;charset=utf-8," + escape(text);
      parent.window.frames['formFrame'].style.border="5px solid green";
    };

    xhr.onerror = function() {
      alert('Woops, there was an error making the request.');
    };
    xhr.send();
  }

  function createCORSRequest(method, url) {
    var xhr = new XMLHttpRequest();
    if ("withCredentials" in xhr) {
      xhr.open(method, url, true);
    }else if (typeof XDomainRequest != "undefined") {
      xhr = new XDomainRequest();
      xhr.open(method, url);
    }else {
      xhr = null;
    }
    return xhr;
  } 
</script>