ura.design/bower_components/foundation/js/foundation/foundation.magellan.js

;(function ($, window, document, undefined) {
  'use strict';

  Foundation.libs['magellan-expedition'] = {
    name : 'magellan-expedition',

    version : '5.5.2',

    settings : {
      active_class : 'active',
      threshold : 0, // pixels from the top of the expedition for it to become fixes
      destination_threshold : 20, // pixels from the top of destination for it to be considered active
      throttle_delay : 30, // calculation throttling to increase framerate
      fixed_top : 0, // top distance in pixels assigend to the fixed element on scroll
      offset_by_height : true,  // whether to offset the destination by the expedition height. Usually you want this to be true, unless your expedition is on the side.
      duration : 700, // animation duration time
      easing : 'swing' // animation easing
    },

    init : function (scope, method, options) {
      Foundation.inherit(this, 'throttle');
      this.bindings(method, options);
    },

    events : function () {
      var self = this,
          S = self.S,
          settings = self.settings;

      // initialize expedition offset
      self.set_expedition_position();

      S(self.scope)
        .off('.magellan')
        .on('click.fndtn.magellan', '[' + self.add_namespace('data-magellan-arrival') + '] a[href*=#]', function (e) {
          var sameHost = ((this.hostname === location.hostname) || !this.hostname),
              samePath = self.filterPathname(location.pathname) === self.filterPathname(this.pathname),
              testHash = this.hash.replace(/(:|\.|\/)/g, '\\$1'),
              anchor = this;

          if (sameHost && samePath && testHash) {
            e.preventDefault();
            var expedition = $(this).closest('[' + self.attr_name() + ']'),
                settings = expedition.data('magellan-expedition-init'),
                hash = this.hash.split('#').join(''),
                target = $('a[name="' + hash + '"]');

            if (target.length === 0) {
              target = $('#' + hash);

            }

            // Account for expedition height if fixed position
            var scroll_top = target.offset().top - settings.destination_threshold + 1;
            if (settings.offset_by_height) {
              scroll_top = scroll_top - expedition.outerHeight();
            }
            $('html, body').stop().animate({
              'scrollTop' : scroll_top
            }, settings.duration, settings.easing, function () {
              if (history.pushState) {
                        history.pushState(null, null, anchor.pathname + '#' + hash);
              }
                    else {
                        location.hash = anchor.pathname + '#' + hash;
                    }
            });
          }
        })
        .on('scroll.fndtn.magellan', self.throttle(this.check_for_arrivals.bind(this), settings.throttle_delay));
    },

    check_for_arrivals : function () {
      var self = this;
      self.update_arrivals();
      self.update_expedition_positions();
    },

    set_expedition_position : function () {
      var self = this;
      $('[' + this.attr_name() + '=fixed]', self.scope).each(function (idx, el) {
        var expedition = $(this),
            settings = expedition.data('magellan-expedition-init'),
            styles = expedition.attr('styles'), // save styles
            top_offset, fixed_top;

        expedition.attr('style', '');
        top_offset = expedition.offset().top + settings.threshold;

        //set fixed-top by attribute
        fixed_top = parseInt(expedition.data('magellan-fixed-top'));
        if (!isNaN(fixed_top)) {
          self.settings.fixed_top = fixed_top;
        }

        expedition.data(self.data_attr('magellan-top-offset'), top_offset);
        expedition.attr('style', styles);
      });
    },

    update_expedition_positions : function () {
      var self = this,
          window_top_offset = $(window).scrollTop();

      $('[' + this.attr_name() + '=fixed]', self.scope).each(function () {
        var expedition = $(this),
            settings = expedition.data('magellan-expedition-init'),
            styles = expedition.attr('style'), // save styles
            top_offset = expedition.data('magellan-top-offset');

        //scroll to the top distance
        if (window_top_offset + self.settings.fixed_top >= top_offset) {
          // Placeholder allows height calculations to be consistent even when
          // appearing to switch between fixed/non-fixed placement
          var placeholder = expedition.prev('[' + self.add_namespace('data-magellan-expedition-clone') + ']');
          if (placeholder.length === 0) {
            placeholder = expedition.clone();
            placeholder.removeAttr(self.attr_name());
            placeholder.attr(self.add_namespace('data-magellan-expedition-clone'), '');
            expedition.before(placeholder);
          }
          expedition.css({position :'fixed', top : settings.fixed_top}).addClass('fixed');
        } else {
          expedition.prev('[' + self.add_namespace('data-magellan-expedition-clone') + ']').remove();
          expedition.attr('style', styles).css('position', '').css('top', '').removeClass('fixed');
        }
      });
    },

    update_arrivals : function () {
      var self = this,
          window_top_offset = $(window).scrollTop();

      $('[' + this.attr_name() + ']', self.scope).each(function () {
        var expedition = $(this),
            settings = expedition.data(self.attr_name(true) + '-init'),
            offsets = self.offsets(expedition, window_top_offset),
            arrivals = expedition.find('[' + self.add_namespace('data-magellan-arrival') + ']'),
            active_item = false;
        offsets.each(function (idx, item) {
          if (item.viewport_offset >= item.top_offset) {
            var arrivals = expedition.find('[' + self.add_namespace('data-magellan-arrival') + ']');
            arrivals.not(item.arrival).removeClass(settings.active_class);
            item.arrival.addClass(settings.active_class);
            active_item = true;
            return true;
          }
        });

        if (!active_item) {
          arrivals.removeClass(settings.active_class);
        }
      });
    },

    offsets : function (expedition, window_offset) {
      var self = this,
          settings = expedition.data(self.attr_name(true) + '-init'),
          viewport_offset = window_offset;

      return expedition.find('[' + self.add_namespace('data-magellan-arrival') + ']').map(function (idx, el) {
        var name = $(this).data(self.data_attr('magellan-arrival')),
            dest = $('[' + self.add_namespace('data-magellan-destination') + '=' + name + ']');
        if (dest.length > 0) {
          var top_offset = dest.offset().top - settings.destination_threshold;
          if (settings.offset_by_height) {
            top_offset = top_offset - expedition.outerHeight();
          }
          top_offset = Math.floor(top_offset);
          return {
            destination : dest,
            arrival : $(this),
            top_offset : top_offset,
            viewport_offset : viewport_offset
          }
        }
      }).sort(function (a, b) {
        if (a.top_offset < b.top_offset) {
          return -1;
        }
        if (a.top_offset > b.top_offset) {
          return 1;
        }
        return 0;
      });
    },

    data_attr : function (str) {
      if (this.namespace.length > 0) {
        return this.namespace + '-' + str;
      }

      return str;
    },

    off : function () {
      this.S(this.scope).off('.magellan');
      this.S(window).off('.magellan');
    },

    filterPathname : function (pathname) {
      pathname = pathname || '';
      return pathname
          .replace(/^\//,'')
          .replace(/(?:index|default).[a-zA-Z]{3,4}$/,'')
          .replace(/\/$/,'');
    },

    reflow : function () {
      var self = this;
      // remove placeholder expeditions used for height calculation purposes
      $('[' + self.add_namespace('data-magellan-expedition-clone') + ']', self.scope).remove();
    }
  };
}(jQuery, window, window.document));