jquery 使用$.ajax 时获取原生XMLHttpRequest 对象

<script>
$('.screenshot_input').change(function (){
//获取file对象 即相当于可以直接post的$_FILES数据
var domFile = $(this)[0].files[0]

var domForm = $('#testForm')[0]
//将form对象直接作为参数 new FormData对象
var formData = new FormData(domForm);
//追加file 对象
formData.append('file',domFile);

$.ajax({
url:'{{ path( 'acme_admin_app_dealAppScreenShot') }}',
type: "POST",
data: formData,
processData: false,  // tell jQuery not to process the data
contentType: false,   // tell jQuery not to set contentType
xhr: function(){        //这是关键  获取原生的xhr对象  做以前做的所有事情
var xhr = jQuery.ajaxSettings.xhr();
xhr.upload.onload = function (){
alert('finish downloading')
}

xhr.upload.onprogress = function (ev) {
if(ev.lengthComputable) {
var percent = 100 * ev.loaded/ev.total;
console.log(percent,ev)
}
}
return xhr;
},
success:function(data){
alert(data)
}
})
})
</script>

Array
(
[name] => cooff
[email] => qq.comaa
)
Array
(
[file] => Array
(
[name] => yunce2.0测试.apk
[type] => application/vnd.android.package-archive
[tmp_name] => /tmp/php4Jxt0c
[error] => 0
[size] => 6476627
)

)