(function ($) {
    var $scrollTo = $.scrollTo = function (target, duration, settings) {
        $(window).scrollTo(target, duration, settings);
    };
    $scrollTo.defaults = {
        axis: 'xy',
        duration: parseFloat($.fn.jquery) >= 1.3 ? 0 : 1
    };
    $scrollTo.window = function (scope) {
        return $(window)._scrollable();
    };
    $.fn._scrollable = function () {
        return this.map(function () {
            var elem = this,
                isWin = !elem.nodeName || $.inArray(elem.nodeName.toLowerCase(), ['iframe', '#document', 'html', 'body']) != -1;
            if (!isWin) return elem;
            var doc = (elem.contentWindow || elem).document || elem.ownerDocument || elem;
            return $.browser.safari || doc.compatMode == 'BackCompat' ? doc.body : doc.documentElement;
        });
    };
    $.fn.scrollTo = function (target, duration, settings) {
        if (typeof duration == 'object') {
            settings = duration;
            duration = 0;
        }
        if (typeof settings == 'function') settings = {
            onAfter: settings
        };
        if (target == 'max') target = 9e9;
        settings = $.extend({}, $scrollTo.defaults, settings);
        duration = duration || settings.speed || settings.duration;
        settings.queue = settings.queue && settings.axis.length > 1;
        if (settings.queue) duration /= 2;
        settings.offset = both(settings.offset);
        settings.over = both(settings.over);
        return this._scrollable().each(function () {
            var elem = this,
                $elem = $(elem),
                targ = target,
                toff, attr = {},
                win = $elem.is('html,body');
            switch (typeof targ) {
            case 'number':
            case 'string':
                if (/^([+-]=)?\d+(\.\d+)?(px|%)?$/.test(targ)) {
                    targ = both(targ);
                    break;
                }
                targ = $(targ, this);
            case 'object':
                if (targ.is || targ.style) toff = (targ = $(targ)).offset();
            }
            $.each(settings.axis.split(''), function (i, axis) {
                var Pos = axis == 'x' ? 'Left' : 'Top',
                    pos = Pos.toLowerCase(),
                    key = 'scroll' + Pos,
                    old = elem[key],
                    max = $scrollTo.max(elem, axis);
                if (toff) {
                    attr[key] = toff[pos] + (win ? 0 : old - $elem.offset()[pos]);
                    if (settings.margin) {
                        attr[key] -= parseInt(targ.css('margin' + Pos)) || 0;
                        attr[key] -= parseInt(targ.css('border' + Pos + 'Width')) || 0;
                    }
                    attr[key] += settings.offset[pos] || 0;
                    if (settings.over[pos]) attr[key] += targ[axis == 'x' ? 'width' : 'height']() * settings.over[pos];
                } else {
                    var val = targ[pos];
                    attr[key] = val.slice && val.slice(-1) == '%' ? parseFloat(val) / 100 * max : val;
                }
                if (/^\d+$/.test(attr[key])) attr[key] = attr[key] <= 0 ? 0 : Math.min(attr[key], max);
                if (!i && settings.queue) {
                    if (old != attr[key]) animate(settings.onAfterFirst);
                    delete attr[key];
                }
            });
            animate(settings.onAfter);

            function animate(callback) {
                $elem.animate(attr, duration, settings.easing, callback &&
                function () {
                    callback.call(this, target, settings);
                });
            };
        }).end();
    };
    $scrollTo.max = function (elem, axis) {
        var Dim = axis == 'x' ? 'Width' : 'Height',
            scroll = 'scroll' + Dim;
        if (!$(elem).is('html,body')) return elem[scroll] - $(elem)[Dim.toLowerCase()]();
        var size = 'client' + Dim,
            html = elem.ownerDocument.documentElement,
            body = elem.ownerDocument.body;
        return Math.max(html[scroll], body[scroll]) - Math.min(html[size], body[size]);
    };

    function both(val) {
        return typeof val == 'object' ? val : {
            top: val,
            left: val
        };
    };
})(jQuery);
$(document).ready(function () {
    var s = $('.scroll-here');
    var curr = -1,
        node;
    $(document).keydown(function (e) {
        switch (e.keyCode) {
        case 39:
        case 74:
            node = s[++curr];
            if (node) {
                $.scrollTo(node, 800);
            } else {
                curr = s.length - 1;
            }
            break;
        case 37:
        case 75:
            node = s[--curr];
            if (node) {
                $.scrollTo(node, 800);
            } else {
                curr = 0;
            }
            break;
        }
    });
    
});