javascript - How to append empty string to FormData -

i have ajax script sends formdata object via ajax.

the code looks this:

fd = new formdata(); fd.append('title', $('.some_input').val()); // few other appends including file  jquery.ajax({   url: 'some_url',   datatype: 'json',   processdata: false,   contenttype: false,   data: fd }) 

when $('.some_input').val() not empty, works predicted, server gets necessary param. in case of input value empty string behaves missing append. how can put empty string formdata in case?