Custom function in GAS that takes eBay item URL and returns item category

eBayItemCategory.gs

function getCategory(itemUrl) {
  var itemID = itemUrl.slice(itemUrl.lastIndexOf('/') + 1);
  Logger.log(itemID);
  
  var parameters = 
     "?callname=GetSingleItem" +
     "&responseencoding=JSON" +
     "&appid=" + "YourAppIDHere" +
     "&siteid=0" +
     "&version=963" +
     "&ItemID=" + itemID;
  
  var result = JSON.parse(UrlFetchApp.fetch("http://open.api.ebay.com/shopping" + parameters).getContentText());
  var category = result.Item.PrimaryCategoryID;
  
  return category;
}