HTML

html form using http

edit & run code by clicking it<form method="GET" action="example/message.html">
  <p>Name: <input type="text" name="name"></p>
  <p>Message:<br><textarea name="message"></textarea></p>
  <p><button type="submit">Send</button></p>
</form>

http form

var formElement = document.getElementById("myFormElement");
var xhr = new XMLHttpRequest();
xhr.open("POST", "submitform.php");
xhr.send(new FormData(formElement));

http form

var formData = new FormData();

formData.append("username", "Groucho");
formData.append("accountnum", 123456);
formData.append("afile", fileInputElement.files[0]);

var xhr = new XMLHttpRequest();
xhr.open("POST", "http://foo.com/submitform.php");
xhr.send(formData);

http form

var formElement = document.getElementById("myFormElement");
formData = new FormData(formElement);
formData.append("serialnumber", serialNumber++);
xhr.send(formData);