hi! i am using squarespace. unfortunately i am not able to customize the gallery as i'd like through the user control panel, unless i use the advanced options to create additional code.

here is the existing javascript:
Code:
Y.use('squarespace-gallery-stacked', function(Y) {
  Y.on('domready', function() {


    // Mobile Nav ///////////////////////////////////

     Y.one('#mobileMenuLink a').on('click', function(e){
       var mobileMenuHeight = parseInt(Y.one('#mobileNav .wrapper').get('offsetHeight'),10);
       if (Y.one('#mobileNav').hasClass('menu-open')) {
         new Y.Anim({ node: Y.one('#mobileNav'), to: { height: 0 }, duration: 0.5, easing: 'easeBoth' }).run();
         new Y.Anim({ node: Y.one('#headerWrapper'), to: { top: 0 }, duration: 0.5, easing: 'easeBoth' }).run();
       } else {
         new Y.Anim({ node: Y.one('#mobileNav'), to: { height: mobileMenuHeight }, duration: 0.5, easing: 'easeBoth' }).run();
         new Y.Anim({ node: Y.one('#headerWrapper'), to: { top: mobileMenuHeight }, duration: 0.5, easing: 'easeBoth' }).run();
       }
       
       Y.one('#mobileNav').toggleClass('menu-open');
     });


    // NAV DROPDOWNS //////////////////////////////////////////

    /* on click*/
    Y.all('nav.dropdown-click > ul').each( function(n) {
      n.delegate('click', function(e){
        folderToggle(e.currentTarget.next('.subnav'));
      }, 'li.folder a');
    });


    /* on hover */
    Y.all('nav.dropdown-hover > ul').each( function(n) {
      var timer;
      n.delegate(['mouseover','mousemove'], function(e){
        folderOpen(e.currentTarget.one('.subnav'));
        if (timer) { timer.cancel(); }
        timer = Y.later(700, this, function() {
          folderClose(e.currentTarget.one('.subnav'));
        });
      }, 'li.folder');
    });


    // GALLERY PAGES ///////////////////////////////////////////////////

    if (Y.one('body').hasClass('collection-type-gallery')) {

      if(Y.all('#slideshow .slide').size() > 1) {
        gallerySlideshow();
      }
      

      if (Y.Squarespace.Management) {
        Y.Squarespace.Management.on('tweak', function(f){
          if (f.getName() == 'gallery-auto-play') {
            Y.Squarespace.GalleryManager._galleries[0].set('autoplay', Static.SQUARESPACE_CONTEXT.tweakJSON['gallery-auto-play']);
          }
        });
      }
      Y.Global.on('tweak:reset', function(){
        slideshow.fire('refresh');
      });
      Y.Global.on('tweak:close', function(){
        Y.all('.slide img[data-image]' ).each(function(img) {
          img.fire('refresh');
        });
      });
      Y.one('window').on('resize', function(e){
        Y.all('.slide img[data-image]' ).each(function(img) {
          img.fire('refresh');
        });
      });
    }

    // BLOG PAGES ///////////////////////////////////////////////////

    if (Y.one('body').hasClass('collection-type-blog')) {
      var sidebarEl = Y.one('#sidebarWrapper');
       Y.one('#page').setStyle('min-height', sidebarEl.get('offsetHeight'));
    }


    // VERTICAL ALIGN PAGES ////////////////

    if (Y.one('img[data-image]')) {
      if (Y.one('body').hasClass('collection-type-gallery')) {
        vertAlignCanvas();
      } else {
        Y.Squarespace.ImageLoadManager.on('batch-complete', function() { vertAlignCanvas(); });
        // if we haven't heard back from ImageLoadManager yet, go ahead and fire alignment
        Y.later(1000, this, function(){
          vertAlignCanvas();
        });
      }
    } else {
      vertAlignCanvas();
    }

    Y.on('resize', function(){
      vertAlignCanvas();
    });



  });





  // FUNCTIONS

  var bodyWidth = parseInt(Y.one('body').getComputedStyle('width'),10);

  var slideshow;


  function gallerySlideshow() {

    if (bodyWidth < 800) {

      new Y.Squarespace.Loader({
        img:Y.all('img[data-image]')
      });

      Y.one('#slideshowWrapper').addClass('mobile-gallery');

    } else {

      slideshow = new Y.Squarespace.Gallery2({
        container: Y.one('#slideshow'),
        elements: {
          // next: '.nav .next',
          // previous: '.nav .previous',
          // currentIndex: '.nav .currentIndex',
          // totalSlides: '.nav .totalSlides'
        },
        loop: true,
        autoplay: Static.SQUARESPACE_CONTEXT.tweakJSON['gallery-auto-play'],
        design: 'strip',
        designOptions: {
          autoHeight: false,
          speed: 0.8
        }
      });

    }

  }

  // center page if able to
  function vertAlignCanvas() {

    windowHeight = Y.one('body').get('winHeight');
    canvasHeight = Y.one('#canvas').get('offsetHeight');


    if (windowHeight > canvasHeight) {
      Y.one('#canvasWrapper').setStyles({
        height: '100%',
        position: 'relative',
        visibility: 'visible'
      });
      Y.one('#canvas').setStyles({
        marginTop: -(canvasHeight / 2),
        top: '50%',
        position: 'relative'
      });
    } else {
      Y.one('#canvasWrapper').setStyles({
        height: 'auto',
        position: 'relative',
        visibility: 'visible'
      });
      Y.one('#canvas').setStyles({
        marginTop: 0,
        top: 0,
        position: 'relative'
      });
    }

  }


  //////////// NAVIGATION DROPDOWNS /////////////

  var OCV = 105; // OCV = open/close velocity (smaller is slower)

  function folderOpen (ddSubnav) {
    if (ddSubnav.ancestor('li.folder').hasClass('dropdown-open')) {
    } else {
      Y.all('.dropdown-open .subnav').each(function(n){
        folderClose(n);
      });
      new Y.Anim({
        node: ddSubnav,
        to: {
          opacity: 1,
          height: ddSubnav.one('ul').get('offsetHeight')
        },
        duration: (parseInt(ddSubnav.one('ul').get('offsetHeight'),10) / OCV) / 10,
        easing: 'easeOutStrong'
      }).run().on('end', function() {
        ddSubnav.ancestor('li.folder').addClass('dropdown-open');
      });
    }
  }

  function folderClose (ddSubnav) {
    if (ddSubnav.ancestor('li.folder').hasClass('dropdown-open')) {
      new Y.Anim({
        node: ddSubnav,
        to: {
          opacity: 1,
          height: 0
        },
        duration: (parseInt(ddSubnav.one('ul').get('offsetHeight'),10) / OCV) / 10,
        easing: 'easeOutStrong'
      }).run().on('end', function() {
        ddSubnav.ancestor('li.folder').removeClass('dropdown-open');
      });
    }
  }

  function folderToggle (ddSubnav) {
    if (ddSubnav.ancestor('li.folder').hasClass('dropdown-open')) {
      folderClose(ddSubnav);
    } else {
      folderOpen(ddSubnav);
    }
  }


});
I'd like to be able to have the gallery scroll automatically with an arrow at both ends.

Can someone point me to a tutorial or give any advice on how to go about this? I'd really like to learn how to do this. thanks!