jQuery.scrollSpeed/jQuery.scrollSpeed.js at master · techslides/jQuery.scrollSpeed · GitHub

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// Custom scrolling speed with jQuery
// Source: github.com/ByNathan/jQuery.scrollSpeed
// Version: 1.0

(function($) {

    jQuery.scrollSpeed = function(step, speed) {

        var $document = $(document),

            $window = $(window),

            $body = $('html, body'),

            viewport = $window.height(),

            top = 0,

            scroll = false;

        if (window.navigator.msPointerEnabled)

            return false;

        $window.on('mousewheel DOMMouseScroll', function(e) {

            scroll = true;

            if (e.originalEvent.wheelDeltaY < 0 || e.originalEvent.detail > 0)

                top = (top + viewport) >= $document.height() ? top : top += step;

            if (e.originalEvent.wheelDeltaY > 0 || e.originalEvent.detail < 0)

                top = top <= 0 ? 0 : top -= step;

            $body.stop().animate({

                scrollTop: top

            }, speed, 'default', function() {

                scroll = false;

            });

            return false;

        }).on('scroll', function() {

            if (!scroll) top = $window.scrollTop();

        }).on('resize', function() {

            viewport = $window.height();

        });
    };

    jQuery.easing.default = function (x,t,b,c,d) {

        return -c * ((t=t/d-1)*t*t*t - 1) + b;
    };

})(jQuery);