Smooth Scrollminal

gistfile1.js

// shim layer with setTimeout fallback
window.requestAnimFrame = window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    function(callback) {
        window.setTimeout(callback, 1000 / 60);
    };

// $.scroll() function
;(function($) {
    var interpolate = function (source, target, shift) { 
        return (source + (target - source) * shift); 
    };

    var easing = function (pos) { 
        return (-Math.cos(pos * Math.PI) / 2) + 0.5; 
    };

    $.scroll = function(endY, duration, easingF) {
        endY = endY || ($.os.android ? 1 : 0);
        duration = duration || 200;
        (typeof easingF === 'function') && (easing = easingF);

        var startY = window.pageYOffset,
            startT  = Date.now(),
            finishT = startT + duration;

        var animate = function() {
            var now = +(new Date()),
                shift = (now > finishT) ? 1 : (now - startT) / duration;

            window.scrollTo(0, interpolate(startY, endY, easing(shift)));

            (now > finishT) || requestAnimFrame(animate);
        };

        animate();
    };
}(Zepto));