Have long forms? See where people give up.

mktoFormDebug.js

var parentForm = document.querySelector("[id^=mktoForm_]");
parentForm.addEventListener("focusout", doSomething, false);
var formId = document.querySelectorAll('form.mktoForm')[0].getAttribute('id');
 
function doSomething(e) {
   if (e.target !== e.currentTarget) {
       var clickedItem = e.target.id;
       ga('create', 'UA-XXXXXXXX-X');
       ga('send','event','Marketo Form Fillout', formId, clickedItem)
   }
   e.stopPropagation();
}