jquery advace

$(document).ready(function(){
   // cache this query since it's a search by CLASS
   selectable = $(":checked.selectable");
   // when the select/deselect all is clicked, do this function
   $("#selectall").click(selectAll);
   // whenever any individual checkbox is checked, change the text
   // describing how many are checked
   selectable.click(changeNumFilters);
   // calculate how many are initially checked
   changeNumFilters();
});
 
var selectable;
 
function changeNumFilters()
{
   // this needs to be checked on every call
   // since the length can change with every click
   var size = $(":checked.selectable").length;
   if (size > 0)
      $("#selectedCount").html(size);
   else
      $("#selectedCount").html("0");
 }
  
// handles the select/deselect of all checkboxes
function selectAll()
{
   var checked = $("#selectall").attr("checked");
   selectable.each(function(){
      var subChecked = $(this).attr("checked");
      if (subChecked != checked)
      {
         $(this).click();
      }
   });
   changeNumFilters();
   }