Snippet from theme.js

theme.js

jQuery(window).on('load', function() {
	// Add data attribute for each Marketo form wrapper.
	window.FormsPlus = window.FormsPlus || {
	  allDescriptors: {},
	  allMessages: {},
	  detours: {}
	};

	/*! @author Sanford Whiteman @license MIT */
	FormsPlus.tagWrappers = function tagWrappers() {
	  /* common vars & aliases */
	  var ANCESTORS_STOR = '.mktoFormRow, .mktoFormCol',
	    INPUTS_STOR = 'INPUT,SELECT,TEXTAREA,BUTTON',
	    attrTag = 'data-wrapper-for',
	    _forEach = Array.prototype.forEach;

	  /* utility fn to tag wrapper containers with inner form inputs */
	  function tagMktoWrappers(formEl) {
	    _forEach.call(formEl.querySelectorAll(ANCESTORS_STOR), function(ancestor) {
	      ancestor.setAttribute(attrTag, '');
	      _forEach.call(ancestor.querySelectorAll(INPUTS_STOR), function(input) {
	        var currentTag = ancestor.getAttribute(attrTag);
	        ancestor.setAttribute(attrTag, [currentTag ? currentTag : '', input.id, input.name != input.id ? input.name : ''].join(' ').trim());
	      });
	    });
	  }

	  MktoForms2.whenRendered(function(form) {
	    var formEl = form.getFormElem()[0];
	    tagMktoWrappers(formEl);
	  });

	};

	FormsPlus.tagWrappers();
});