Force "overscrolling" at Chrome/Mac with javascript

Question

When you get to the limit of document, you can keep scrolling and can see an background behing the document before it bounces back (overscrolling).

How can I force the window to overscroll like this with javascript?

Answer 1

This is not the ultimate solution since I think the animation is imperfect and it's really only for desktops, but it can at least get you started. What I have done is increase the height of the body for animation on scroll.

 $(document).on('scroll mousewheel', function (e) {
    //Check for mousewheel scrolling down (or not used at all)
    if (!e.originalEvent || !e.originalEvent.wheelDeltaY
       || e.originalEvent.wheelDeltaY < 0) {
       if ($(window).height() + $(this).scrollTop() == $(this).height()) {
          //Prevent simultaneous triggering of the animation
          if (!$("body").data('bouncing')) {
             $("body").height(function (_, h) { return h + 15; })
                 .data('bouncing', true);
             $("body, html").animate({
                'scrollTop': '+=15'
             }, 125).animate({
                'scrollTop': '-=15'
             }, {duration: 125, complete: function () {
                $(this).height(function (_, h) { return h - 15; })
                    .data('bouncing', false);
             }});
          }
       }
    }
 }).on('keydown', function (e) {
    //The "down" arrow; still bounces when pressed at the bottom of the page
    if (e.which == '40') {
       $(this).trigger('scroll');
    }
 });