Function fileUploadXhr

static/js/jquery.form.js:282–341

(a)

        // XMLHttpRequest Level 2 file uploads (big hat tip to francois2metz)
        function fileUploadXhr(a) {
            var formdata = new FormData();

            for (var i=0; i < a.length; i++) {
                formdata.append(a[i].name, a[i].value);
            }

            if (options.extraData) {
                var serializedData = deepSerialize(options.extraData);
                for (i=0; i < serializedData.length; i++) {
                    if (serializedData[i]) {
                        formdata.append(serializedData[i][0], serializedData[i][1]);
                    }
                }
            }

            options.data = null;

            var s = $.extend(true, {}, $.ajaxSettings, options, {
                contentType: false,
                processData: false,
                cache: false,
                type: method || 'POST'
            });

            if (options.uploadProgress) {
                // workaround because jqXHR does not expose upload property
                s.xhr = function() {
                    var xhr = $.ajaxSettings.xhr();
                    if (xhr.upload) {
                        xhr.upload.addEventListener('progress', function(event) {
                            var percent = 0;
                            var position = event.loaded || event.position; /*event.position is deprecated*/
                            var total = event.total;
                            if (event.lengthComputable) {
                                percent = Math.ceil(position / total * 100);
                            }
                            options.uploadProgress(event, position, total, percent);
                        }, false);
                    }
                    return xhr;
                };
            }

            s.data = null;
            var beforeSend = s.beforeSend;
            s.beforeSend = function(xhr, o) {
                //Send FormData() provided by user
                if (options.formData) {
                    o.data = options.formData;
                }
                else {
                    o.data = formdata;
                }
                if(beforeSend) {
                    beforeSend.call(this, xhr, o);
                }
            };