Pagination debug

gistfile1.js

 Backbone.View.extend({

        // root view DOM-element
        tagName: "div",

        // events for root view DOM-element
        events: {
            "click .go_back": "back",
            "click .go_forward": "forward",
            "click .active a": "fire",
            "click a.page": "change_page"
        },

        // This function is executed
        // when view is created
        initialize: function(options) {
            var self = this;
            if (options === undefined) {
                options = {};
            }
            this.options = options;
        },

        // proceeds to one page back
        back: function() {
            if (this.options.position > this.options.first_page) {
                this.set_page(parseInt(this.options.position) - 1);
            }
        },

        // proceeds to one page forward
        forward: function() {
            if (this.options.position < this.options.last_page) {
                this.set_page(parseInt(this.options.position) + 1);
            }
        },

        // shows current page value
        fire: function() {
            this.set_page(this.options.position);
        },

        // page click event handler
        change_page: function(e) {
            this.set_page($(e.target).html());
        },

        // sets current page value
        set_page: function(page) {
            this.options.position = page;
            this.$el.find("li.active a").html(page);
            this.trigger('page_change', {
                "page": page,
                "limit": this.options.record_limit
            });
            this.render();
        },

        // renders page list:
        render: function() {
            var pages,
                options = this.options,
                page_list = [],
                last_page_length;

            switch (options.mode) {
                case "centered":
                    // * using usual centered mode
                    page_list = this.centered_pagination(
                        options.first_page,
                        options.last_page,
                        parseInt(options.position),
                        options.radius
                    );
                    break;
                case "advanced":
                    // * using advanced mode
                    page_list = this.advanced_pagination(
                        options.first_page,
                        options.last_page,
                        parseInt(options.position),
                        options.edge_radius,
                        options.position_radius
                    );
                    break;
            }

            // Render page template
            pages = JST.bootstrap_pagination_plist({
                "pages": page_list,
                "current": this.options.position
            });

            // Replace element contents with new pages
            this.$el.html("").append(pages).find("li");
        },

        // ### Basic centered pagination page list generator
        centered_pagination: function(first_page, last_page, position, radius) {
            // * first_page - page, where page list starts
            // * last_page - page, where page list ends
            // * position - active page
            // * radius - amount of pages around current

            // For testing, please use:
            //     
            //     var test_pagination = new window.structuredUI.Pagination(), i;
            //     for (i = -10; i <= 10; i++) {
            //         console.log(test_pagination.centered_pagination(-10, 10, i, 2));
            //     }
            var pages = [],
                i,
                range_gen = function(start, end, current) {
                    var pages = [];
                    for (i = start; i < end; i++) {
                        pages.push(i);
                    }
                    return pages;
                };

            // Page list generation, where:
            switch (true) {
                // - page is located near the center
                case (position - radius > first_page && position + radius <= last_page):
                    pages = range_gen(position - radius, position + radius, position);
                    break;
                    // - page is located near the left corner
                case (position >= first_page && position <= first_page + radius):
                    pages = range_gen(first_page, first_page + (radius * 2), position);
                    break;
                    // - page is located near the right corner
                case (position >= last_page - radius && position <= last_page):
                    pages = range_gen(last_page - (radius * 2) + 1, last_page + 1, position);
                    break;
            }
            return (pages);
        },

        // ### Advanced pagination page list generator
        advanced_pagination: function(first_page, last_page, position, edge_radius, position_radius) {
            // * first_page - page, where page list starts
            // * last_page - page, where page list ends
            // * position - current page in pagination list
            // * edge_radius - radius from edges
            // * position_radius - radius around current page


            // For testing, please use:
            //     
            //     var test_pagination = new window.structuredUI.Pagination(), i;
            //     for (i = -10; i <= 10; i++) {
            //         console.log(test_pagination.advanced_pagination(-10, 10, i, 2, 2));
            //     }
            return Array.apply(null, new Array(last_page + 1 - first_page)).map(function(e, i, a) {
                return Math.min(
                    Math.min(
                        Math.max(1 + i - edge_radius, 0),
                        Math.max(a.length - i - edge_radius, 0)
                    ),
                    Math.max(Math.abs(i - (position - first_page)) - position_radius, 0)
                );
            }).map(function(e, i, a) {
                return e * Math.max(a[i - 1], a[i + 1]) > 0 ? '...' : (i + first_page).toString();
            }).filter(function(e, i, a) {
                return e != '.' || a[i - 1] != '...';
            });
        }

    });