Unable to get uploaded file name or path in requestBody in webRequest.UploadData on browser.webRequest.onBeforeRequest event

I want to uploaded file path or file name in browser.webRequest.onBeforeRequest event of my web extension for firefox. . help appreciated in advanced .

function logURL(requestDetails) 
{


    if(requestDetails.requestBody)
    {

        if (requestDetails.requestBody.raw)
        {
            for (var e of requestDetails.requestBody.raw)
            {
                if(e.file)
                {
                    console.log("raw file inside: "+ e.file);
                }

            }
        }
       if(requestDetails.requestBody.formData)
       {
           var dictionary = requestDetails.requestBody.formData;
           for (var key in dictionary)
           {         
               console.log("form data : key=" + key + ", value=" + dictionary[key]);

           }
       }
    }

}

browser.webRequest.onBeforeRequest.addListener(

 logURL,
 {urls: ["<all_urls>"]},["requestBody"]
);

i expected output as uploaded file name but the actual output is file: