Express导出类模块，还是在授权方案中导出类的实例？

Question

我有一个UserAuth类来管理我的用户访问控制。该类在这样的模块中：

const user_permission = require("../middleware/user_permission.json");

class UserAuth {
  constructor(keys) {
    this.keys = keys;
  }

  // returning true if user have permission
  can(id, perm) {
    let auth = false;
    if (!id || !perm) {
      console.log("error");
    } else {
      this.keys.forEach(key => {
        if (key.userId == id && key.permissionId == perm) {
          auth = true;
        }
      });
    }
    return auth;
  }

  // return permission array
  allow(id, perm) {
    const data = { userId: id, permissionId: perm };
    if (!id || !perm) {
      console.log("no input");
    } else {
      this.keys.forEach(key => {
        if (id !== key.userId || perm === key.permissionId) {
          console.log("id non esiste oppure permesso esiste");
        } else {
          this.keys.push(data);
        }
      });
    }
    return (this.keys = this.removeDuplicates(this.keys));
  }

  // return permission array
  disallow(id, perm) {
    if (!id || !perm) {
      console.log("error");
    } else {
      const result = this.keys.findIndex(data => {
        return data.userId === id && data.permissionId === perm;
      });
      this.keys.splice(result, 1);
    }
    return (this.keys = this.removeDuplicates(this.keys));
  }

  removeDuplicates(arr) {
    const userIds = [];
    const result = arr.filter((element, index, array) => {
      var tempArr = element.userId + "" + element.permissionId;
      if (userIds.indexOf(tempArr) === -1) {
        userIds.push(tempArr);
        return element;
      }
    });
    result.sort((a, b) => {
      return a.userId - b.userId;
    });
    return result
  }
}

//const auth = new UserAuth(user_permission);

module.exports.UserAuth = UserAuth;
//module.exports.auth = auth;

我不知道导出类或类本身的距离是否更好。如果导出类，则可以在新模块中将config json数组user_permission传递到auth模块之外，但是我不知道是否有副作用。我也想在中间代码中继续使用该类作为中间件

最好的方法是什么？

谢谢