ExampleAJAX3-get-cities.js

<script type="text/javascript" runat="server">

  Platform.Load("core", "1");
  var authCookie = Platform.Request.GetCookieValue('auth');

  if (authCookie) {

    var state = Request.GetQueryStringParameter("state");
    var citiesDE = DataExtension.Init("Cities");
    var cities = citiesDE.Rows.Lookup(["state"], [state], 100);
    cities = cities ? cities : "";
    //Write('{"results":' + Stringify(cities) +',"debug":[{"authCookie":"'+authCookie+'"}]}');
    Write('{"results":' + Stringify(cities) + '}');

  }

</script>