FB: Canvas - Scroll To Top

facebook.scrollTop.js

// Function for returning the user to any 'y' position in a Facebook app/tab. Uses jQuery animate, otherwise gracefully falls-back without it.
// Source[1]: http://stackoverflow.com/questions/7193425/how-do-you-animate-fb-canvas-scrollto
// Source[2]: https://developers.facebook.com/docs/reference/javascript/FB.Canvas.scrollTo/

var scrollY = function (y) {
    if (window.jQuery) {
        FB.Canvas.getPageInfo (function (pageInfo) {
            $({ y: pageInfo.scrollTop })
                .animate({
                        y: y
                    },
                    {
                        duration: 1000,
                        step: function (offset) {
                            FB.Canvas.scrollTo(0, offset);
                    }
                });
        });
    } else {
        FB.Canvas.scrollTo(0, y);
    }
};