How to implement Isotope with Pagination
<p>I am trying to implement isotope with pagination on my WordPress site (which obviously is a problem for most people). I've come up with a scenario which may work if I can figure a few things out.</p>

<p>On my page, I have this part of my isotope script -
</p>

<pre><code>$('.goforward').click(function(event) {
    var href = $(this).attr('href');
    $('.isotope').empty();
    $('.isotope').load(href +".html .isotope &gt; *");
    $( 'div.box' ).addClass( 'isotope-item' );
    $container.append( $items ).isotope( 'insert', $items, true );
    event.preventDefault();
});
</code></pre>

<p>Then I am using this pagination function which I modified from <a href="http://www.kriesi.at/archives/how-to-build-a-wordpress-post-pagination-without-plugin" rel="noreferrer">here</a> to have the 'goforward' class --
</p>

<pre><code>function isotope_pagination($pages = '', $range = 2)
{  
     $showitems = ($range * 2)+1;  

     global $paged;
     if(empty($paged)) $paged = 1;

     if($pages == '')
     {
         global $wp_query;
         $pages = $wp_query-&gt;max_num_pages;
         if(!$pages)
         {
             $pages = 1;
         }
     }   

     if(1 != $pages)
     {
         echo "&lt;div class='pagination'&gt;";
         for ($i=1; $i &lt;= $pages; $i++)
         {
             if (1 != $pages &amp;&amp;( !($i &gt;= $paged+$range+1 || $i &lt;= $paged-$range-1) || $pages &lt;= $showitems ))
             {
                 echo ($paged == $i)? "&lt;a href='".get_pagenum_link($i)."' class='inactive goforward'&gt;".$i."&lt;/a&gt;":"&lt;a href='".get_pagenum_link($i)."' class='inactive goforward' &gt;".$i."&lt;/a&gt;";
             }
         }
         echo "&lt;/div&gt;\n";
     }
}
</code></pre>

<p><strong>1st Problem</strong> - I'm having issues with the filtering/sorting. It filters fine for the first page, but doesn't sort. On the second page or any other page loaded it does not append/insert or even filter/sort when starting fresh on that page. Instead, when trying to do so it gives me this error --</p>

<pre><code>Uncaught TypeError: Cannot read property '[object Array]' of undefined
</code></pre>

<p><strong>2nd Problem</strong> - When loading the page fragments, there's a delay and the current page is still visible before the next page fragment is loaded in its place.</p>

<p>I know a lot of people have problems with isotope and pagination, usually, end up using infinite scroll even though isotope author does not recommend it.</p>

<p>So my theory is loading content via load() and have a callback of some sort to only display filtered items.</p>

<p>Any ideas on how to achieve this?</p>

<p>My entire isotope script --- 
</p>

<pre><code>$(function () {
    var selectChoice, updatePageState, updateFiltersFromObject,
    $container = $('.isotope');
    $items = $('.item');  

    ////////////////////////////////////////////////////////////////////////////////////
    /// EVENT HANDLERS
    ////////////////////////////////////////////////////////////////////////////////////
        //////////////////////////////////////////////////////
        // Mark filtering element as active/inactive and trigger filters update
        $('.js-filter').on( 'click', '[data-filter]', function (event) {
          event.preventDefault();
          selectChoice($(this), {click: true});
          $container.trigger('filter-update');
        });
        //////////////////////////////////////////////////////
        // Sort filtered (or not) elements
        $('.js-sort').on('click', '[data-sort]', function (event) {
          event.preventDefault();
          selectChoice($(this), {click: true});
          $container.trigger('filter-update');
        });
        //////////////////////////////////////////////////////
        // Listen to filters update event and update Isotope filters based on the marked elements
        $container.on('filter-update', function (event, opts) {
          var filters, sorting, push;
          opts = opts || {};
          filters = $('.js-filter li.active a:not([data-filter="all"])').map(function () {
            return $(this).data('filter');
          }).toArray();
          sorting = $('.js-sort li.active a').map(function () {
            return $(this).data('sort');
          }).toArray();
          if (typeof opts.pushState == 'undefined' || opts.pushState) {
            updatePageState(filters, sorting);
          }
          $container.isotope({
            filter: filters.join(''),
            sortBy: sorting
          });

        });
        //////////////////////////////////////////////////////
        // Set a handler for history state change
        History.Adapter.bind(window, 'statechange', function () {
          var state = History.getState();
          updateFiltersFromObject(state.data);
          $container.trigger('filter-update', {pushState: false});
        });
        ////////////////////////////////////////////////////////////////////////////////////
        /// HELPERS FUNCTIONS
        ////////////////////////////////////////////////////////////////////////////////////
        //////////////////////////////////////////////////////
        // Build an URI to get the query string to update the page history state
        updatePageState = function (filters, sorting) {
          var uri = new URI('');
          $.each(filters, function (idx, filter) {
            var match = /^\.([^-]+)-(.*)$/.exec(filter);
            if (match &amp;&amp; match.length == 3) {
              uri.addSearch(match[1], match[2]);
            }
          });
          $.each(sorting, function (idx, sort) {
            uri.addSearch('sort', sort);
          });
          History.pushState(uri.search(true), null, uri.search() || '?');
        };
        //////////////////////////////////////////////////////
        // Select the clicked (or from URL) choice in the dropdown menu
        selectChoice = function ($link, opts) {
          var $group = $link.closest('.btn-group'),
              $li = $link.closest('li'),
              mediumFilter = $group.length == 0;
          if (mediumFilter) {
            $group = $link.closest('.js-filter');
          }

          if (opts.click) {
            $li.toggleClass('active');
          } else {
            $li.addClass('active');
          }
          $group.find('.active').not($li).removeClass('active');
          if (!mediumFilter) {
            if ($group.find('li.active').length == 0) {
              $group.find('li:first-child').addClass('active');
            }
            $group.find('.selection').html($group.find('li.active a').first().html());
          }
        };
        //////////////////////////////////////////////////////
        // Update filters by the values in the current URL
        updateFiltersFromObject = function (values) {
          if ($.isEmptyObject(values)) {
            $('.js-filter').each(function () {
                selectChoice($(this).find('li').first(), {click: false});
            });
            selectChoice($('.js-sort').find('li').first(), {click: false});
          } else {
            $.each(values, function (key, val) {
              val = typeof val == 'string' ? [val] : val;
              $.each(val, function (idx, v) {
                var $filter = $('[data-filter=".' + key + '-' + v + '"]'),
                    $sort = $('[data-sort="' + v + '"]');
                if ($filter.length &gt; 0) {
                  selectChoice($filter, {click: false});
                } else if ($sort.length &gt; 0) {
                  selectChoice($sort, {click: false});
                }
              });
            });
          }
        };
        ////////////////////////////////////////////////////////////////////////////////////
        /// Initialization
        ////////////////////////////////////////////////////////////////////////////////////
        //////////////////////////////////////////////////////
        // Initialize Isotope
    $container.imagesLoaded( function(){
        $container.isotope({
            masonry: { resizesContainer: true },
            itemSelector: '.item',
            getSortData: {
                date: function ( itemElem ) {
                    var date = $( itemElem ).find('.thedate').text();
                    return parseInt( date.replace( /[\(\)]/g, '') );
                },
            area: function( itemElem ) { // function
                var area = $( itemElem ).find('.thearea').text();
                return parseInt( area.replace( /[\(\)]/g, '') );
            },
            price: function( itemElem ) { // function
                var price = $( itemElem ).find('.theprice').text();
                return parseInt( price.replace( /[\(\)]/g, '') );
            }
        }
    });

    var total = $(".next a:last").html();
    var pgCount = 1;
    var numPg = total;
    pgCount++;

    $('.goback').click(function() {
        $('.isotope').empty();
        $('.isotope').load("/page/&lt;?php echo --$paged;?&gt;/?&lt;?php echo $_SERVER["QUERY_STRING"]; ?&gt;.html .isotope &gt; *");
        $container.append( $items ).isotope( 'insert', $items, true );
        $( 'div.box' ).addClass( 'isotope-item' );
   });

   $('.goforward').click(function(event) {
       var href = $(this).attr('href');
       $('.isotope').empty();
       $('.isotope').load(href +".html .isotope &gt; *");
       $( 'div.box' ).addClass( 'isotope-item' );
       $container.append( $items ).isotope( 'insert', $items, true );
       event.preventDefault();
   });
});
        //////////////////////////////////////////////////////
        // Initialize counters
        $('.stat-count').each(function () {
          var $count = $(this),
              filter = $count.closest('[data-filter]').data('filter');
          $count.html($(filter).length);
        });
        //////////////////////////////////////////////////////
        // Set initial filters from URL
        updateFiltersFromObject(new URI().search(true));
        $container.trigger('filter-update', {pushState: false});
      }); 
});
</code></pre>