code: function() {
        var links = this._links,
          rules = this._rules,
          args = slice.call(arguments);
  
          for (var i in links) {
            var link = links[i],
              retain = link[1],
              index = parseInt(link[0]);
              if (args[index] && (rule = rules[i])) {
                rule.action.apply(this, args.slice(index, index + retain));
                return "";
              }
          }
        return "";
      }
docs: __`this.parser`__的依赖方法， 即遍历links检查是否有子匹配满足关系， 有则推入对应的action数组, 注意由于其是是replace方法的调用，每次都要返回""完成 reduce操作