Any reason why having a javascript timer fire every 2.5 second for an ajax request to my own callback(listed below) that all it does is return the contents of 2 _session variables would take up so much resources?

John

function refreshcarttimer() {
    print($_SESSION['num_items'] . ',' .  $_SESSION['uc_price']);
    return;
}

/**
 * Implementation of hook_menu().
 */

function product_type_menu() {
  $items = array();

  $items['cart/refreshcarttimer'] = array(
    'title' => 'Refresh Shopping Cart',
    'description' => 'Refresh Shopping Cart',
    'page callback' => 'refreshcarttimer',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );
  return $items;
} 

On Sun, Feb 6, 2011 at 2:10 AM, John Mitchell <mitchelljj98@gmail.com> wrote:
I have a javascript timer set to fire every 2.5 seconds so that I can set the current values for the items and total for the shopping cart summary.  I would like to be able to get these values from client side cookies or javascript global variables so that I don't have to make an ajax call to the server but I have found that the DOM elements are not accessible within the javascript function unless I run an ajax request to a page (listed below) and after it returns then the DOM elements are accessible (i.e. $(".num-items").html(numItems);) and now I can update them.  Having these ajax requests run every 2.5 seconds for every client will not scale.

How can I make Drupal DOM elements accessible within a javascript function without having to do an ajax request to a page?

Thanks,

John

    setInterval('updateShoppingCartInfo()', 2500);

    function updateShoppingCartInfo(){
        var xmlHttpReq = new XMLHttpRequest();
        var url = 'https://' + document.domain + '/cart/refreshcarttimer';
        xmlHttpReq.open('post', url, true);
        xmlHttpReq.onreadystatechange = function() {
               if (xmlHttpReq.readyState != 4)  {
                   return;
               }
            else {
                var responseText = xmlHttpReq.responseText;
                                var numItems = responseText.substr(0,responseText.indexOf(","));
                                var ucPrice = responseText.substr(responseText.indexOf(",")+1);
                                $(".num-items").html(numItems);
                                $(".uc-price").html(ucPrice);
            }              
        }
        xmlHttpReq.send(null);
    }     


--
John J. Mitchell



--
John J. Mitchell