Javascript: Carrossel Boilerplate

carrossel-boilerplate.js

var Carrossel = (function(){

            var instance, itemHeight, itemWidth, allItensWidth = 0;

            function init( instanceId, options ) {
                instance = $('#'+instanceId);                

                $( instance )
                    .delegate('.carrossel-widget-nav-prev', 'click', prev)
                    .delegate('.carrossel-widget-nav-next', 'click', next);                  

                configSizes();
            }

            function configSizes(){
                var sample = instance.find('.carrossel-widget-images li:first');

                itemHeight = sample.height();
                itemWidth = sample.width();
                allItensWidth = itemWidth * instance.find('.carrossel-widget-images li').length;

                $('.carrossel-widget-images').width(allItensWidth);

            }

            function getInstance(){
                return instance;
            }

            function next(){
                var next = getActiveItem().next();
                if( !next.length ) {
                    next = getFirstItem();
                }                               

                goToItem( next );
            }

            function prev(){
                var prev = getActiveItem().prev();
                if( !prev.length ) {
                    prev = getLastItem();
                }                               

                goToItem( prev );
                
            }

            function goToItem( item ){
                setActiveItem( item );

                var prevPosition = ( itemWidth * (item.prevAll().length) ) * -1; 
                goToPosition(prevPosition);

            }

            function setActiveItem( item ){
                $('.carrossel-widget-item-active').removeClass('carrossel-widget-item-active');
                item.addClass('carrossel-widget-item-active');
            }

            function getActiveItem(){
                return instance.find('.carrossel-widget-item-active');
            }

            function getFirstItem(){
                return instance.find('.carrossel-widget-images li:first');
            }

            function getLastItem(){
                return instance.find('.carrossel-widget-images li:last');
            }

            function goToPosition( position ) {
                console.log(position+'px')
                instance.find('.carrossel-widget-images').css('margin-left', position+'px');
            }

            return {
                getInstance: getInstance,
                init: init,
                next: next,
                prev: prev
            };

        })();

        $(function(){
            Carrossel.init('carrossel-1');

        });