jQuery プリロードページャープラグイン（事前読み込み & スクロール監視）

jquery.preloadpager.js

(function($) {
    $.preloadPager = function(options) {
        var settings = $.extend({
            autoLoad: true,
            cache: false,
            content: '.content',
            pager: '#pager',
            margin: $(window).height()
        }, options);

        var autoLoad = settings.autoLoad,
            didScroll = false,
            nowLoading = false,
            timer,
            $content = $(settings.content),
            $pager = $(settings.pager),
            nextUrl = $pager.attr('href'),
            $cache;

        var remain = function(element) {
            var $element = $(element),
                eBottom  = $element.offset().top + $element.height(),
                wBottom  = $(document).scrollTop() + $(window).height();
            return ( eBottom - settings.margin < wBottom );
        }

        var monitor = function() {
            if ( !didScroll ) return;
            didScroll = false;
            if ( !remain(settings.content) ) return;
            appendContent();
        };

        var preload = function() {
            if ( !nextUrl ) return;
            nowLoading = true;
            var onSuccess = function(data) {
                if ( settings.loadCallback ) {
                    data = settings.loadCallback(data);
                }
                var $data = $(data);
                nextUrl = $data.find(settings.pager).attr('href');
                $cache  = $data.find(settings.content).children();
                nowLoading = false;
            };
            $.ajax({ url: nextUrl, cache: settings.cache, success: onSuccess });
        };

        var appendContent = function() {
            if ( settings.appendCallback ) settings.appendCallback();
            $content.append($cache);
            if ( nextUrl ) {
                preload();
            } else {
                if ( autoLoad ) window.clearInterval(timer);
            }
        };

        if ( autoLoad ) {
            $pager.hide();
            $(window).scroll(function() {
                didScroll = true;
            });
            timer = window.setInterval(monitor, 200);
        } else {
            $pager.click(appendContent);
        }

        preload();
    };
})(jQuery);