Helper for adding global Ajax callbacks manualy from console. See https://stackoverflow.com/questions/5202296/add-a-hook-to-all-ajax-requests-on-a-page and https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Using_XMLHttpRequest#Monitoring_progress
Install as bookmarklet.
addAjaxCallback(function() {console.log(this.responseText);});