ajaxFileUpload只能上传一次，和上传同名图片不能上传等bug问题

createUploadForm: function (id, fileElementId)
    {
        //create form
        var formId = ‘jUploadForm‘ + id;
        var fileId = ‘jUploadFile‘ + id;
        var form = $(‘<form  action="" method="POST" name="‘ + formId + ‘" id="‘ + formId + ‘" enctype="multipart/form-data"></form>‘);
        var oldElement = $(‘#‘ + fileElementId);

        var newElement = $(oldElement).clone(true).val(""); //核心
//        var newElement = $(oldElement).clone(true);
//        oldElement.after(oldElement.clone().val(""));


        $(oldElement).attr(‘id‘, fileId);
        $(oldElement).before(newElement);
        $(oldElement).appendTo(form);
        //set attributes
        $(form).css(‘position‘, ‘absolute‘);
        $(form).css(‘top‘, ‘-1200px‘);
        $(form).css(‘left‘, ‘-1200px‘);
        $(form).appendTo(‘body‘);
        return form;
    },