Smooth Scroll

smoothscroll.js

if (window.jQuery) {
    (function ($, w, d) {
        var $d = $(d);
        $d.ready(function () {
            $d.on("click", "a[data-smooth-scroll]", function (event) {
                var $this = $(this),
                    href = $this.attr("href");

                if (href.indexOf("#") === 0) {

                    event.preventDefault();

                    var scrollTop = $(w).scrollTop(),
                        height = parseInt($d.height(), 10),
                        offset = $(href).offset().top,
                        speed = $this.data("scrollSpeed");

                    if (!speed) {
                        $this.data("scrollSpeed", (speed = 1000))
                    }

                    // Normalise the speed of scroll.
                    var distance = scrollTop - offset;

                    // Make sure the distance is always positive.
                    if (distance < 0) {
                        distance *= -1;
                    }

                    // v = d/t - multiply for milliseconds.
                    var time = (distance / height) * speed,
                        called = false;

                    $("html, body").animate({
                        scrollTop: offset
                    }, {
                        duration: time,
                        complete: function () {
                            // Prevent dupliction of complete call by binding to both html and body.
                            if (!called) {
                                called = true;
                                w.location.hash = href;
                            }
                        }
                    });
                }
            });
        });
    }(jQuery, window, document));
}