Way to make inheritance in Vuex modules

I put my reusable vuex code in small classes. E.g.

crud.js

export default class {
    constructor ( endpoint ) {
       this.state = {
          endpoint: endpoint,
          meta:     {},
          status:   null,
          known:    [],
          currentId: null,
       };
       this.getters = {
          id: state => id => state.known.find( o => o.id === id )
       };
       this.actions = {
          async store( context, payload ) {
               *(call to API)*
          },
          async update( context, payload ) {
               *(call to API)*
          },
          *...etc*
      };
      this.mutations = {
         STORED(state, item) {
            state.known.push(item);
         },
         *...etc*
      };
   }
}

Then I can use it in all of my modules:

user.module.js

import Crud from '/crud';
var crud = new Crud('/api/users');

const state = {
   ...crud.state,
};
const getters = {
   ...crud.getters,
};
const actions = {
   ...crud.actions,
};
const mutations = {
   ...crud.mutations,
};

export default {
   namespaced: true,
   state,
   getters,
   actions,
   mutations
};

Developing a little bit more Erin's response, you can define a base class with common features like this:

export default class BaseModule {
    protected state() {
        return {
            isLoading: false,
        };
    };
    protected getters() {
        return {
            isLoading(s) {
                return s.isLoading;
            },
        };
    };
    protected actions() {
        return {};
    };
    protected mutations() {
        return {
            [START_TRANSACTION]: (s) => {
                s.isLoading = true;
            },
            [END_TRANSACTION]: (s) => {
                s.isLoading = false;
            },
        };
    }
    protected modules() {
        return {};
    };

    public getModule = () => {
        return {
            namespaced: true,
            state: this.state(),
            getters: this.getters(),
            actions: this.actions(),
            mutations: this.mutations(),
            modules: this.modules(),
        };
    }
}

You can now extend/override only the parts you need in derived classes, with class inheritance; for example, if you need to extend the modules...:

import BaseModule from './BaseModule';
import rowDensity from '@/store/modules/reusable/rowDensity';

export default class ItemListModule extends BaseModule {  
  protected modules() {
    return {
      ...super.modules(),
      rowDensity,
    };
  };
}

Finally, to use them as modules in the store, you can instantiate them and call .getModule():

import Vue from 'vue';
import Vuex from 'vuex';
import ItemListModule from './modules/ItemListModule';

Vue.use(Vuex);

const debug = process.env.NODE_ENV !== 'production';

export const MODULE_NAMESPACES = {
  List: 'list',
};

export default new Vuex.Store({
  modules: {
    [MODULE_NAMESPACES.List]: new ItemListModule().getModule(),
  },
  strict: debug,
});