Webix Uploader improvement sugestion

function WebixSenderAdvanced(sender, callback) {
    this.sender = function () {
        if (sender == null)
            return null;

        if (sender._settings != null || sender.s != null)
            return sender;

        if (sender.view !== null)
            return $$(sender.id);

        return sender;
    }();
    this.callback = callback;
}

WebixSenderAdvanced.prototype = function () {
    var sender;
    var callback;

    var debugMode;
    var fileItem;
    var formData;

    var send = function (file) {
        sender = this.sender;
        callback = this.callback;
        getDebugStatus();
        getFileObject(file);
        createXhrObject();
        compileFormData.apply(this, arguments);
        post();
    }

    function getDebugStatus() {
        debugMode = (sender._settings != null);
    }

    function getFileObject(file) {
        fileItem = (typeof (file) === 'number')
            ? fileItem = sender.files.getItem(file)
            : file;

        if (fileItem == null || fileItem.status !== 'client')
            return;

        fileItem.status = 'transfer';
    }

    function createXhrObject() {
        if (fileItem == null) return;

        var xhr = fileItem.xhr = new XMLHttpRequest();
        var id = fileItem.id;

        if (debugMode)
            createXhrObjectDebug(xhr, id);
        else
            createXhrObjectRelease(xhr, id);
    }
    function createXhrObjectDebug(xhr, id) {
        var progress = 'progress';
        xhr.upload.addEventListener(progress, webix.bind(function (e) {
            this._update_progress(id, e.loaded / e.total * 100);
        }, sender), false);
        xhr.onload = webix.bind(function () {
            this._file_complete(id);
            callback();
        }, sender);
    }
    function createXhrObjectRelease(xhr, id) {
        var progress = 'progress';
        xhr.upload.addEventListener(progress, webix.bind(function (e) {
            this.hs(id, e.loaded / e.total * 100);
        }, sender), false);
        xhr.onload = webix.bind(function () {
            this.is(id);
            callback();
        }, sender);
    }

    function compileFormData() {
        if (fileItem == null) return;

        formData = new FormData();
        formData.append(fileItem.name, fileItem.file);

        for (var i = 1; i < arguments.length; i++) {
            var parameter = arguments[i];
            if (parameter == null) continue;

            Object.keys(parameter).forEach(function (key) {
                if (key != null)
                    formData.append(key, parameter[key]);
            });
        }
    }

    function post() {
        if (fileItem == null) return;

        var id = fileItem.id;
        var url = debugMode
            ? sender._settings.upload
            : sender.s.upload;

        fileItem.percent = 0;
        sender.files.updateItem(id);

        fileItem.xhr.open('POST', url, true);
        fileItem.xhr.send(formData);
    }

    return {
        send: send
    }
}();