Make sidebar scroll able along with page and stop at footer

scroll.js

(function($) {
  //id of sidebar
    var element = $('#sidebar')
    originalY = $(element).offset().top;

        // Space between element and top of screen (when scrolling)
        var topMargin = 20;
        // Should probably be set in CSS; but here just for emphasis
        element.css('position', 'relative');
        $(window).on('scroll', function(event) {
            var scrollTop = $(window).scrollTop();
            footer_view = scrollTop + $('#sidebar').height();
            if(footer_view >= $('#footer').offset().top ){
                element.stop(false, false).animate({
                    top:  ($('#footer').offset().top - $('#sidebar').height() - 200)}, 300);    
                //element.stop()
            }
            else{
                element.stop(false, false).animate({
                    top: scrollTop < originalY ? 0 : scrollTop - originalY + topMargin }, 300);
            }
        });
})(jQuery);