javascript - Naming and posting forms with FormData and XMLHTTPrequest -

i'm doing exercise javascript, , i'm after couple of hours still stuck. have html form:

<form method=post name=transferform   action="/transfer.php"> <input name=user type=text value=""> <input name=credits type=text value=""> <input type=submit name=submission value="send"> </form> 

i want invoke javascript posts form (filled in values), using xmlhttprequest , formdata. i've come far, , me seems correct doesn't seem work:

var formdata = new formdata(); formdata.append('user', 'bob'); formdata.append('credits', '1'); var xhr = new xmlhttprequest(); xhr.open('post', 'http://someurl.com/transfer.php');   xhr.send(formdata);  

using script not work, doesn't post form. however, manually pressing 'send' in html page post form, , well. suspicion doesn't work because haven't set name of form in request(the html form named "transferform"). can't figure out how name formdata-object request.

i'm giving script of out context (it's part of larger exercise involving web application provided me play with), hope can me anyway :)

i've been using this reference.

new formdata() encoded differently form submit.

the default enctype="application/x-www-form-urlencoded".

using new formdata() means using enctype="multipart/form-data".