i have a visualforce page that source code is

<apex:page sidebar="false" showHeader="false">
   <link type="text/css" href="//ajax.aspnetcdn.com/ajax/jquery.ui/1.10.1/themes/smoothness/jquery-ui.min.css" rel="stylesheet" />

 <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
 <script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.10.3/jquery-ui.min.js"></script>
 <script src="//cdn.jsdelivr.net/xdate/0.8/xdate.min.js"></script>

<script>
 $(function() {

    var clearChatter = function(){
        $('.feedcontainer .feeditem').each(function(idx, el){
            $(el).remove();
        });

    }
    //set date value to today
    var today = new XDate(), current = today.clone();
    $( "#slider" ).slider({
      value:30,
      min: 1,
      max: 30,
      step: 1,
      stop: function( event, ui ) {

        //calculate the date, subtract months
        current = today.clone().addDays(-30+ui.value);
        $( "#date" ).html(current.clone().addDays(-1).toString('dd MMMM yyyy'));

        //clean out all old chatter posts
        clearChatter();

        //start loading new chatter
        var dayStart = new XDate(current.getFullYear(), current.getMonth(), current.getDate());
        var dayEnd = dayStart.clone().addDays(1);
        //check on feed container
        //add her if she's not there
        if($('.cxshowmorefeeditemscontainer').length == 0){
            var container = '<div class="cxshowmorefeeditemscontainer showmorefeeditemscontainer"></div>';

            $('.feedcontainer').append(container);

        }

        chatter.getFeed().showMoreFeedItems(this, {paginationToken: dayStart.toISOString()});


      },
      orientation: 'vertical'
    });
    $( "#date" ).val( "$" + $( "#slider" ).slider( "value" ) );


  });
  </script>
  <div id="date" style="position:absolute; left:720px;">Today</div>
  <div style="height:300px; position:absolute; left:700px;" id="slider"></div>
  <chatter:newsfeed ></chatter:newsfeed>
</apex:page>

as i can see

chatter.getFeed().showMoreFeedItems(this, {paginationToken: dayStart.toISOString()});

without calling apex they are getting chatter.getFeed(). is there any link or documentation on chatter for getting feed using javascript with various filters please guideline.