How to automate expiration of jQuery BBQ cache after some defined time?

Question

I am using this code:

$(function () {

            // For each .bbq widget, keep a data object containing a mapping of
            // url-to-container for caching purposes.
            $('.bbq').each(function () {
                $(this).data('bbq', {
                    cache: {
                        // If url is '' (no fragment), display this div's content.
                        '': $(this).find('.bbq-default')
                    }
                });
            });

            // For all links inside a .bbq widget, push the appropriate state onto the
            // history when clicked.
            $('.bbq a[href^=#]').live('click', function (e) {
                var state = {},

                  // Get the id of this .bbq widget.
                  id = $(this).closest('.bbq').attr('id'),

                  // Get the url from the link's href attribute, stripping any leading #.
                  url = $(this).attr('href').replace(/^#/, '');

                // Set the state!
                state[id] = url;
                $.bbq.pushState(state);

                // And finally, prevent the default link click behavior by returning false.
                return false;
            });

            // Bind an event to window.onhashchange that, when the history state changes,
            // iterates over all .bbq widgets, getting their appropriate url from the
            // current state. If that .bbq widget's url has changed, display either our
            // cached content or fetch new content to be displayed.
            $(window).bind('hashchange', function (e) {

                // Iterate over all .bbq widgets.
                $('.bbq').each(function () {
                    var that = $(this),

                      // Get the stored data for this .bbq widget.
                      data = that.data('bbq'),

                      // Get the url for this .bbq widget from the hash, based on the
                      // appropriate id property. In jQuery 1.4, you should use e.getState()
                      // instead of $.bbq.getState().
                      url = $.bbq.getState(that.attr('id')) || '';

                    // If the url hasn't changed, do nothing and skip to the next .bbq widget.
                    if (data.url === url) { return; }

                    // Store the url for the next time around.
                    data.url = url;

                    // Remove .bbq-current class from any previously "current" link(s).
                    that.find('a.bbq-current').removeClass('bbq-current');

                    // Hide any visible ajax content.
                    that.find('.bbq-content').children(':visible').hide();

                    // Add .bbq-current class to "current" nav link(s), only if url isn't empty.
                    url && that.find('a[href="#' + url + '"]').addClass('bbq-current');

                    if (data.cache[url]) {
                        // Since the widget is already in the cache, it doesn't need to be
                        // created, so instead of creating it again, let's just show it!
                        data.cache[url].show();


                    } else {
                        // Show "loading" content while AJAX content loads.
                        that.find('.bbq-loading').show();

                        // Create container for this url's content and store a reference to it in
                        // the cache.
                        data.cache[url] = $('<div class="bbq-item"/>')

                          // Append the content container to the parent container.
                          .appendTo(that.find('.bbq-content'))

                          // Load external content via AJAX. Note that in order to keep this
                          // example streamlined, only the content in .infobox is shown. You'll
                          // want to change this based on your needs.
                          .load(url, function () {
                              // Content loaded, hide "loading" content.
                              that.find('.bbq-loading').hide();
                          });
                    }
                });
            })

            // Since the event is only triggered when the hash changes, we need to trigger
            // the event now, to handle the hash the page may have loaded with.
            $(window).trigger('hashchange');

        });

from here: http://benalman.com/code/projects/jquery-bbq/examples/fragment-advanced/

It is caching the dynamically loaded content. I want to expire this cache after every 10 seconds. I am not so pro at JQuery. How can I achieve this? Please help!

UPDATE

I tried this code:

<script type="text/javascript" src="jquery.timer.js"></script>
<script type="text/javascript">
        var timer = $.timer(function () {
        $('.bbq').removeData('.bbq-content');
        });

        timer.set({ time: 5000, autostart: true });
</script>

The code is reaching $('.bbq').removeData('.bbq-content'); line every 5 seconds, but its not clearing the cache. Unable to show updated results. Please help!

Answer 1

You don't need to clear cached data every 10 seconds; you just need to check whether the cached data is older than 10 seconds before showing it.

First, we need a place to save timestamps for each piece of cached data. Replace the first chunk of code with this:

            $('.bbq').each(function () {
                $(this).data('bbq', {
                    cache: {
                        // If url is '' (no fragment), display this div's content.
                        '': $(this).find('.bbq-default')
                    },
                    cacheTimes: {} // <-- this line is new (plus the comma above)
                });
            });

Then, when a hashchange event occurs, we need the current time:

            // Bind an event to window.onhashchange that, when the history state changes,
            // iterates over all .bbq widgets, getting their appropriate url from the
            // current state. If that .bbq widget's url has changed, display either our
            // cached content or fetch new content to be displayed.
            $(window).bind('hashchange', function (e) {

                var now = (new Date()).getTime(); // <-- this line is new

                // Iterate over all .bbq widgets.
                $('.bbq').each(function () {

And for each widget, we check if enough time has elapsed to invalidate the cache:

                      // Get the url for this .bbq widget from the hash, based on the
                      // appropriate id property. In jQuery 1.4, you should use e.getState()
                      // instead of $.bbq.getState().
                      url = $.bbq.getState(that.attr('id')) || '';

                    // this chunk is new
                    if (url !== '' && now - (data.cacheTimes[url] || 0) > 10000) { // 10 seconds
                        data.url = null;
                        if (data.cache[url]) {
                            data.cache[url].remove();
                            data.cache[url] = null;
                        }
                    }

                    // If the url hasn't changed, do nothing and skip to the next .bbq widget.
                    if (data.url === url) { return; }

When fetching data, we remember the current time:

                        // Show "loading" content while AJAX content loads.
                        that.find('.bbq-loading').show();

                        data.cacheTimes[url] = now; // <-- this line is new

                        // Create container for this url's content and store a reference to it in
                        // the cache.
                        data.cache[url] = $('<div class="bbq-item"/>')