code: function (searchElement, fromIndex) {
                      /// <signature helpKeyword="WinJS.Binding.ListBase.lastIndexOf">
                      /// <summary locid="WinJS.Binding.ListBase.lastIndexOf">
                      /// Gets the index of the last occurrence of the specified value in a list.
                      /// </summary>
                      /// <param name="searchElement" type="Object" locid="WinJS.Binding.ListBase.lastIndexOf_p:searchElement">The value to locate in the list.</param>
                      /// <param name="fromIndex" type="Number" integer="true" optional="true" locid="WinJS.Binding.ListBase.lastIndexOf_p:fromIndex">The index at which to begin the search. If fromIndex is omitted, the search starts at the last index in the list.</param>
                      /// <returns type="Number" integer="true" locid="WinJS.Binding.ListBase.lastIndexOf_returnValue">The index of the last occurrence of a value in a list, or -1 if not found.</returns>
                      /// </signature>
                      fromIndex = asNumber(fromIndex);
                      var length = this.length;
                      fromIndex = Math.min(this._normalizeIndex(fromIndex !== undefined ? fromIndex : length), length - 1);
                      var i;
                      for (i = fromIndex; i >= 0; i--) {
                          var item = this.getItem(i);
                          if (item && item.data === searchElement) {
                              return i;
                          }
                      }
                      return -1;
                  }
docs: ABSTRACT: indexOfKey(key)