jQuery plugin for a custom responsive image carousel. Found from the depths of my Dropbox

bmm-carousel.js

/**
* @version 0.1 Alpha
* @author Timo Laak 6/6/2013
*
*/
(function($) {
    /**
    * Constants for recurring use
    */
    var constants = {
        /** @const */
        PLUGIN_NAME: 'bmmCarousel',
        PLUGIN_CSS_CLASS: 'bmm-carousel'
    };

    /**
    * Templates for repeating elements
    */
    var templates = {
        overlayLeft: '<div class="carousel-overlay" id="left-overlay"></div>',
        overlayRight: '<div class="carousel-overlay" id="right-overlay"></div>',
        carouselNav: '<div class="carousel-nav"></div>',
        btnNext: '<i class="btn-next"></i>',
        btnPrev: '<i class="btn-prev"></i>'
    };

    /**
    * Plugin methods
    */
    var methods = {
        /**
        * Init the plugin
        */
        init: function(options) {
            // Add identifying class for css styles
            this.addClass(constants.PLUGIN_CSS_CLASS);

            this.data('length', $('.carousel-item', this).length);

            // Build the carousel, add overlay, buttons and add bindings
            methods.buildCarousel.apply(this);
            methods.addOverlay.apply(this);
            methods.addButtons.apply(this);
            methods.addBindings.apply(this);
        },
        /**
        * Build the carousel
        */
        buildCarousel: function() {

            var _head, _tail, _tailClone, _this = this, _data = this.data(), carousel = this.children('.carousel');

            _head = $('.carousel-item', this).first();
            _tail = $('.carousel-item', this).last();

            // Do not show items outside the page wrapper if there are less than 3 of them
            if (_data.length < 3) {
                this.addClass('overlay-opaque');
            }

            if (_data.length < 2) {
                this.addClass('no-navigation');
            }
            // If there are only 3 items, clone the last item to the front to prevent
            // showing empty slot
            if (_data.length == 2 || _data.length == 3) {
                _tail.clone().prependTo(carousel);
                _head = $('.carousel-item').first();
                _data.length++;
            }

            // Single item width as percentages
            _data.itemWidth = 100 / _data.length;


            $('.carousel-item', this).each(function() {
                $(this).width(_data.itemWidth + '%');
            });

            $(carousel).width(this.width() * _data.length);

            if (_data.length > 1) {
                // Active item is the second item
                $(carousel).css('left', '-100%');
            }
        },
        /**
        * Add the transparent overlay to cover overflow items
        */
        addOverlay: function() {
            this.append($(templates.overlayLeft));
            this.append($(templates.overlayRight));
        },
        /**
        * Add control buttons
        */
        addButtons: function() {
            var carouselNav = $(templates.carouselNav),
                _btnNext = $(templates.btnNext),
                _btnPrev = $(templates.btnPrev),
                _this = this;

            _btnNext.on('click', function(e) {
                methods.next.apply(_this);
            });

            _btnPrev.on('click', function(e) {
                methods.prev.apply(_this);
            });

            carouselNav.append(_btnNext);
            carouselNav.prepend(_btnPrev);

            this.append(carouselNav);
        },
        /**
        * Add bindings for events
        */
        addBindings: function() {
            var _this = this;
            $(window).on('resize', function() {
                methods.resize.apply(_this);
            });
        },
        /**
        * Rotate carousel forward
        */
        next: function() {
            var _this = this, _data = this.data(), carousel = this.children('.carousel');

            // Return if already rotating to prevent multiple button clicks
            if (_data.rotating === true) {
                return;
            }

            // Start rotating
            _data.rotating = true;

            // Offset is one item to the left of the carousel
            // Animate to two items on the left
            $(carousel).animate({
                left: '-200%'
            }, 'slow', 'swing', function() {

                // Remove the first item and clone the second one (the new first) to the end of the carousel
                $('.carousel-item', _this).first().remove();
                $('.carousel-item', _this).first().clone().appendTo(carousel);

                // Update position back to one item on the left and stop rotating
                $(carousel).css('left', '-100%');
                _data.rotating = false;
            });
        },
        /**
        * Rotate carousel backwards
        */
        prev: function() {
            var _this = this, _data = this.data(), carousel = this.children('.carousel');

            // Return if already rotating to prevent multiple button clicks
            if (_this.data('rotating') === true) {
                return;
            }

            // Start rotating
            _data.rotating = true;

            // Clone last item to front and remove the last item to keep length the same
            $('.carousel-item', _this).last().prev().clone().prependTo(carousel);
            $('.carousel-item', _this).last().remove();

            // Offset is 2 items to the left in the beginning and there are 2 items on the left of the active one
            $(carousel).css('left', '-200%');
            // Animate 1 item to the right. There will be 1 item on the left of the active one in the end
            $(carousel).animate({
                left: '-100%'
            }, 'slow', 'swing', function() {
                _data.rotating = false;
            });
        },
        /**
        * Handle resize events
        */
        resize: function() {
            $('.carousel', this).width(this.width() * this.data('length'));
        }
    };

    /**
    * The actual plugin
    */
    $.fn[constants.PLUGIN_NAME] = function(method) {

        this.each(function() {
            _this = $(this);
            if ( methods[method] ) {
                return methods[method].apply( _this, Array.prototype.slice.call( arguments, 1 ));
            } else if ( typeof method === 'object' || ! method ) {
                return methods.init.apply( _this, arguments );
            } else {
                $.error( 'Method ' +  method + ' does not exist on bmmCarousel' );
            }
        });
    };
})(jQuery);