Taking the following code:
// Bind the click event to the thumbnails.
$(\"ul.hpList\").on(\"click\", \"a.hpThumb\", function (event) {
event
It's not clear to me what you're actually trying to find, but:
Use event.target inside your handler to determine which actual DOM element triggered the event.
Use $(this) to determine which DOM element the handler is attached to, which may be the same thing or may be a parent of the event target.
Use .closest() to find an element's closest ancestor which fits a given selector.