My version of Array reduce

reduce function

it("Should reduce", function () {

            var result;
            var _ = {
                reduce: function () {

                    var reduce = function (arr, func) {

                        var i = 0;
                        var len = arr.length;
                        var running;

                        for (i; i < len; i++) {

                            if (i === 0) {
                                running = func(arr[i], arr[i + 1]);
                                i++;
                            } else {

                                running = func(running, arr[i]);
                            }
                        }

                        return running;
                    };

                    if (Array.prototype.reduce) {

                        _.reduce = function (someArr, someFunc) {
                            return someArr.reduce(someFunc);
                        };

                    } else {
                        _.reduce = reduce;
                    }


                    return _.reduce(arguments[0], arguments[1]);


                }
            };

            result = _.reduce([0, 1, 2, 3], function (one, two) {

                return one + two;
            });

            expect(result).toBe(6);
        });