jquery - Javascript: TypeError: Value does not implement interface FormData -

i'm trying use formdata send data via ajax php script. there doesn't seem problem input type text values when try append files error typeerror: value not implement interface formdata.

i new formdata, searched on web , couldn't find doc on error.

here's form :

<form id="item_form" class="item_form" enctype="multipart/form-data">     <div class="">         <label for="emp_photos">photos</label>         <input id="emp_photos" class="inputtext" type="file" value="" name="emp_photos">     </div> </form> 

here's javascript :

var formdata = new formdata();       formdata.append('photos', $('#emp_photos').files[0]); 

here's error in firebug :

typeerror: value not implement interface formdata.   ...igger("ajaxcomplete",[n,p]),--b.active||b.event.trigger("ajaxstop")))}return n},...  jquery....min.js (line 5) 

what doing wrong here ?

edit: ajax part

$.ajax({    type: 'post',    url: '";     echo $_session["url_base"];    echo "operations/add_employes',    data: formdata,    xhr: function() {  // custom xhr       myxhr = $.ajaxsettings.xhr();       if(myxhr.upload) { // check if upload property exists          myxhr.upload.addeventlistener('progress',progresshandlingfunction, false); // handling progress of upload       }       return myxhr;    },    success: function(msg) {/*...*/}  }); 

var inputs = $("input[type=file]"),     files = [];  // jquery or javascript have different notation // it's either accessing functions () or arrays [] depending on object you're holding @ moment (var = 0; < inputs.length; i++){     files.push(inputs.eq(i).prop("files")[0]);     //files.push(inputs[i].files[0]);     //filename = inputs[i].files[0].name;     //filesize = inputs[i].files[0].size; }  if (formdata) {     // can use array notation of input's `name` attribute here     formdata.append("emp_photos[]", files); }