code: function getSearchableIndexFormAttrs(isindexStartTagToken) {
      var indexAction = Tokenizer.getTokenAttr(isindexStartTagToken, ATTRS.ACTION),
          attrs = [];
  
      if (indexAction !== null) {
          attrs.push({
              name: ATTRS.ACTION,
              value: indexAction
          });
      }
  
      return attrs;
  }
docs: Searchable index building utils (<isindex> tag)