Obtain label id's from loaded slots within GPT

getLabelIds.js

/**
 * Gets the label IDs from all currently loaded GPT slots.
 *
 * @return {Array)} The collected label ids.
 */
function getLabelIds() {
  // declare our output array.
  var labels = [];
  // for looping over the slots
  function getlabels(slot) {
    // get our labelIds
    var rsp = slot.getResponseInformation() && slot.getResponseInformation().labelIds || [];
    // Filter for new ids in this slot.
    var updates = rsp.filter(function(item) {
      return labels.indexOf(item) < 0;
    });
    // Update the labels array.
    labels = labels.concat(updates);
  }

  // Loop over the slots and get all the IDs.
  window.googletag.pubads().getSlots().map(getlabels);
  return labels;
}