PardotFormHandlerUtils.js

// Creates iframe to submit lead data to pardot
// @paramList should be in the format param1=something&param2=somethingelse
function submitPardotLead(formHandlerUrl = '//localhost/no-valid-form-handler-url',
                                 paramList = 'noparams=provided',
                                 callbackFn = function() {}) {

  // build URL
  var srcUrl = formHandlerUrl + '?' + paramList;

  // create iframe el
  const bodyEl = document.querySelector('body');
  var iframeEl = document.createElement('iframe');
  iframeEl.setAttribute('src', srcUrl);
  iframeEl.setAttribute('class', 'pardot-form-handler');
  iframeEl.setAttribute('width', '0');
  iframeEl.setAttribute('height', '0');
  iframeEl.setAttribute('style', 'width: 0px; height: 0px; display: none !important;');

  // once the iframe is loaded, fire the callback
  iframeEl.addEventListener('load', function(){
    callbackFn();
  });

  // appending it with the proper src tag is the same as submitting the form
  bodyEl.appendChild(iframeEl);

}