Check uncheck jquery plugin

I needed check all - uncheck all checkboxes feature to be added to lots of pages in one of my site, so thought of creating a jquery plugin for it, so that i would not have to write same piece of code here and there. So here's the plugin, if Check All checkbox is checked all the sub checkboxes are checked and vice-versa, and if Check All is checked and then any of the sub checkboxes is unchecked, then Check All will also be unchecked.

(function($) {
 $.fn.extend({
  checkun: function(options) {
   var defaults = {
    chkAllName : "",
    chkBoxName : ""
   }
   var options = $.extend(defaults, options);
   var chkAll = options.chkAllName;
   var chkBoxs = options.chkBoxName;
   var chkBoxesLength = $("input[name='"+chkBoxs+"']").length;
   
   $("input[name='"+chkAll+"']").click(function() {
    //get checked state of chkAll checkbox
    var chkState = $(this).attr("checked");
    if(chkState) {
       $("input[name='"+chkBoxs+"']").attr("checked", true);
    }
    else {
     $("input[name='"+chkBoxs+"']").attr("checked", false);
    }
   });
   $("input[name='"+chkBoxs+"']").click(function() {
    var subChkState = $(this).attr("checked");
    if(subChkState) {
     //get the total checkboxes and total checked checkboxes
     var chkedLen = $("input[name='"+chkBoxs+"']:checked").length;
     if(chkedLen == chkBoxesLength) {
      $("input[name='"+chkAll+"']").attr("checked", true);
     }
    }
    else {
     //uncheck the chkAll checkbox
     $("input[name='"+chkAll+"']").attr("checked", false);
    }
   });
  }
 });
})(jQuery);

And to test it, we use the following

//load jquery.js

//  Check All
//
//

Thats it. Hope this helps someone.