gistfile1.js

/*!
 * requires jQuery 
 * usage:
 * Scroller.to({ offset: 100 });
 * Scroller.to({ target: $('#main') });
 *
 * advanced usage (with additional easing function not provided here)
 * Scroller.to({ target: $('#main'), delay: 500, multiplier: 1.5, easing: 'easeOutQuad' });
 */
var Scroller = (function()
{

    var scroll = {

        options: {

            el: $('html:not(:animated),body:not(:animated)'),

            multiplier: 1,

            offset: undefined,

            easing: 'swing',

            delay: 0

        },

        _scrolling: false

    };

    scroll.to = function(options)
    {
        var height = {
                top: $(window).scrollTop(),
                doc: $(document).height(),
                win: $(window).height()
            };

        if (height.doc <= height.win) {
            return;
        }

        var config = $.extend({}, scroll.options);
        config = $.extend(config, options || {});

        config.offset = isNaN(config.offset) ? config.target.offset().top : config.offset;

        var offset   = config.offset,
            distance = Math.abs(height.top - offset);

        if (height.top < offset) {
            var max = height.doc - height.win;
            if (offset > max) {
                distance -= offset - max;
            }
        }
        if (distance) {
            if (scroll._scrolling) {
                scroll.stop();
            }
            scroll._scrolling = true;
            scroll.timeout = window.setTimeout(function() {
                config.el.animate({ scrollTop: Math.floor(offset) }, distance * config.multiplier, config.easing, function()
                {
                    scroll._scrolling = false;
                });
            }, config.delay);
        }
    };

    scroll.stop = function()
    {
        if (scroll.timeout) {
            window.clearTimeout(scroll.timeout);
            scroll.timeout = null;
        }
        scroll.options.el.stop();
        scroll._scrolling = false;
    };

    scroll.isScrolling = function()
    {
        return scroll._scrolling;
    };

    return scroll;

})();