code: function Utilities_getHighAndLowTabIndices(element) {
              var descendants = element.getElementsByTagName("*");
              var lowestTabIndex = 0;
              var highestTabIndex = 0;
              // tabIndex=0 is the highest (considered higher than positive tab indices) so
              // we can stop searching for a higher tab index once we find tabIndex=0.
              var foundTabIndex0 = false;
              for (var i = 0, len = descendants.length; i < len; i++) {
                  var tabIndexStr = descendants[i].getAttribute("tabIndex");
                  if (tabIndexStr !== null && tabIndexStr !== undefined) {
                      var tabIndex = parseInt(tabIndexStr, 10);
                      // Update lowest
                      if (tabIndex > 0 && (tabIndex < lowestTabIndex || lowestTabIndex === 0)) {
                          lowestTabIndex = tabIndex;
                      }
                      // Update highest
                      if (!foundTabIndex0) {
                          if (tabIndex === 0) {
                              foundTabIndex0 = true;
                              highestTabIndex = 0;
                          } else if (tabIndex > highestTabIndex) {
                              highestTabIndex = tabIndex;
                          }
                      }
                  }
              }
  
              return {
                  highest: highestTabIndex,
                  lowest: lowestTabIndex
              };
          }
docs: *element* is not included in the tabIndex search