code: function reveal(el) {
        if (el.hasChildNodes()) {
          // dealing with a container try and find children
          var els = el.querySelectorAll('[data-src], [data-bkg]');
          var elsl = els.length;
          if (elsl === 0) {
            // node has children, but none have the attributes, so reveal
            // the node itself (use case: div with a background)
            doReveal(el);
          } else {
            for (var j = 0; j < elsl; j++) {
              doReveal(els[j]);
            }
          }
        } else {
          doReveal(el);
        }
      }
docs: find what element to work with, as we support containers of images