Yes and of course that's possible :)

<form action=request.php id=register_form>

  <input class='formVal' type=text name=first_name placeholder=First Name>

  <input class='formVal' type=text name=last_name placeholder=LastName>

  <input type=submit value=submit_now onclick=myFunction(); return false;>

</form>

JS

function myFunction()

{

    var elements = document.getElementsByClassName(formVal);

    var formData = new FormData(); 

    for(var i=0; i<elements.length; i++)

    {

        formData.append(elements[i].name, elements[i].value);

    }

    var xmlHttp = new XMLHttpRequest();

        xmlHttp.onreadystatechange = function()

        {

            if(xmlHttp.readyState == 4 && xmlHttp.status == 200)

            {

                alert(xmlHttp.responseText);

            }

        }

        xmlHttp.open(post, server.php); 

        xmlHttp.send(formData); 

}

server.php

<?php

   $firstName = $_POST[first_name];

   $lastName = $_POST[last_name];

   echo $firstName. .$lastName;

   //enter name and lastname into your form and onclick they will be alerted 

?>

Explanation:
Function takes form elements by their class names and stores them in array. Then we create FormData object and loop through elements array for each element and append their name and value to FormData object.
After that we create XMLHttpRequest() object that monitors state and status change during request and also sends data with post method to server.php
When it's over and readystate equals to 4 and status equals to 200, we alert response from server.php, that we save in responseText attribute of XMLHttpRequest object.