isotope/_includes/option-set-buttons.js

      var $optionSets = $('#options .option-set'),
          $optionLinks = $optionSets.find('a');

      $optionLinks.click(function(){
        var $this = $(this);

        // don't proceed if already selected
        if ( $this.hasClass('selected') ) {
          return;
        }
  
        var $optionSet = $this.parents('.option-set');
  
        $optionSet.find('.selected').removeClass('selected');
        $this.addClass('selected');
  
        // make option object dynamically, i.e. { filter: '.my-filter-class' }
        var options = {},
            key = $optionSet.attr('data-option-key'),
            value = $this.attr('data-option-value');
        // parse 'false' as false boolean
        value = value === 'false' ? false : value;
        options[ key ] = value;
  
        $container.isotope( options );
        
        return false;
      });