Unlike jQuery.ajax(), ajaxForm()and the ajaxSubmit()plugin, jQuery forms do not return a jqXHR object. There are other ways to get the jqXHR object:
data() on the form object (easiest way)
ajaxSubmit() . data() , XHR:
var form = $('#myForm').ajaxSubmit({ ... });
var xhr = form.data('jqxhr');
xhr.abort(), .
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beforeSend callback ( jQuery Form 2012 )
jQuery, ajaxForm() ajaxSubmit() jQuery.ajax(). beforeSend, beforeSend(jqXHR, settings).
, beforeSend, jqXHR . jqXHR, abort() jqXHR, .