isotope/_includes/change-sizes.js

      // change size of clicked element
      $container.delegate( '.element', 'click', function(){
        $(this).toggleClass('large');
        $container.isotope('reLayout');
      });

      // toggle variable sizes of all elements
      $('#toggle-sizes').find('a').click(function(){
        $container
          .toggleClass('variable-sizes')
          .isotope('reLayout');
        return false;
      });