Proper way to send an Authenticity Token with AJAX to Rails

This works but gets stopped because it lacks an authenticity token:

$(".ajax-referral").click(function(){
  $.ajax({type: "POST", url: $(this).parent("form").attr("action"), dataType: "script"});
  return false;
});

So I tried adding it like so:

$(".ajax-referral").click(function(){
  $.ajax({type: "POST", url: $(this).parent("form").attr("action") + "?&authenticity_token=" + AUTH_TOKEN, dataType: "script"});
  return false;
});

And it passes the auth_token correctly as a param, but seems to lose the rest of my form.

Anyways to accomplish both sending the form data that works, and the authenticity token as well?

This is a rails environment. And I have this in my head.

= javascript_tag "var AUTH_TOKEN = '#{form_authenticity_token}';" if protect_against_forgery?

Things I've tried

1.

= hidden_field :authenticity_token, :value => form_authenticity_token

2.

$.ajax({type: "POST", url: $(this).parent("form").attr("action"), dataType: "script", authenticity_token: AUTH_TOKEN});

3.

// Always send the authenticity_token with ajax
$(document).ajaxSend(function(event, request, settings) {
    if ( settings.type != 'GET' ) {
        settings.data = (settings.data ? settings.data + "&" : "")
            + "authenticity_token=" + encodeURIComponent( AUTH_TOKEN );
    }
});

Actually, you are reading the action attribute of form and sending a post ajax request to it. to send form data you have to submit the form or you can serialize the form data and send it in ajax request like

$(".ajax-referral").click(function(){
  $.ajax({
      type: "POST", 
      url: $(this).parent("form").attr("action") + "?&authenticity_token=" + AUTH_TOKEN, 
      data:$(this).parent("form").serialize(),
      dataType: "script"
      });
  return false;
});

Doing this will serialize your form data and send it along with ajax request and authenticity token is already being sent via query string