DFP post-rendering callback

Question

I need to trigger some JavaScript after DFP has finished rendering all the ads on the page - or at least when it has triggered collapseEmptyDivs (which

Answer 1

Load script in the part of your page:

// set global variable if not already set
var googletag = googletag || {};
googletag.cmd = googletag.cmd || [];

// load asynchronously the GPT JavaScript library used by DFP,
// using SSL/HTTPS if necessary
(function() {
  var gads   = document.createElement('script');
  gads.async = true;
  gads.type  = 'text/javascript';

  var useSSL = 'https:' === document.location.protocol;
  gads.src = (useSSL ? 'https:' : 'http:') + '//www.googletagservices.com/tag/js/gpt.js';
  var node =document.getElementsByTagName('script')[0];
  node.parentNode.insertBefore(gads, node);
})();

Initialise google publisher tag with the following script, preferable as well in the section of your page:

// can be moved as well in the body
// if using async mode, wrap all the javascript into googletag.cmd.push!
googletag.cmd.push(function() {
  // set page-level attributes for ad slots that serve AdSense
  googletag.pubads().set("adsense_background_color", "FFFFFF");
  googletag.pubads().setTargeting("topic","basketball");

  // enables Single Request Architecture (SRA)
  googletag.pubads().enableSingleRequest();

  // Disable initial load, we will use refresh() to fetch ads.
  // Calling this function means that display() calls just
  // register the slot as ready, but do not fetch ads for it.
  googletag.pubads().disableInitialLoad();

  // Collapses empty div elements on a page when there is no ad content to display.
  googletag.pubads().collapseEmptyDivs();

  // Enables all GPT services that have been defined for ad slots on the page.
  googletag.enableServices();
});

Register slots individually (can be generated with a foreach loop) and render them. The event listener can be registered as well per slot. Here the important part: make sure that you refresh them together to avoid ending up with the same ads on both slots (if the ad is assign to both slots) => googletag.pubads().refresh([slot1, slot2]]);

// this code can be moved externally to improve performance
googletag.cmd.push(function() {
  // define slot1
  slot1 = googletag.defineSlot(
    "/1234/travel/asia/food",
    [728, 90],
    "banner1"
  )
  .addService(googletag.pubads())
  .setTargeting(
    "interests",
    ["sports", "music", "movies"]
  );
  // prerender the slot but don't display it because of disableInitialLoad()
  googletag.display("banner1");

  // define slot2    
  slot2 = googletag.defineSlot(
    "/1234/travel/asia/food",
    [[468, 60], [728, 90], [300, 250]],
    "banner2"
  )
  .addService(googletag.pubads())
  .setTargeting("gender", "male")
  .setTargeting("age", "20-30");

  // prerender the slot but don't display it because of disableInitialLoad()
  googletag.display("banner2");  


  // add event to sign the slot as redered or not
  googletag.pubads().addEventListener('slotRenderEnded', function(event) {
    if (event.slot === slot1 || event.slot === slot2) {
      // do something related to the slot
    }
  });

  // refresh all container ads and show them
  // very important to call refresh with an array to avoid 
  // multiple callback to the registered event 
  googletag.pubads().refresh([slot1, slot2]);
});

After the ad has been rendered, the callback gets triggered.

For more information have a look on this file: https://github.com/davidecantoni/googletag