code: function createPredicateIndexFinder(dir) {
                  return function(array, predicate, context) {
                    predicate = cb(predicate, context);
                    var length = getLength(array);
                    var index = dir > 0 ? 0 : length - 1;
                    for (; index >= 0 && index < length; index += dir) {
                      if (predicate(array[index], index, array)) return index;
                    }
                    return -1;
                  };
                }
docs: Generator function to create the findIndex and findLastIndex functions