javascript - 引用错误: Cannot access 'Player' before initialization

Question

所以我一直在 Nodejs 上使用 ES6 风格的语法和 ESM 模块加载器进行导入/导出。一切都很好，直到我开始收到与导入有关的错误。

错误消息如下:

joseph@InsaneMachine:~/placeholder2/main-server$ npm start

> main-server@1.0.0 start /home/joseph/placeholder2/main-server
> nodemon --experimental-modules src/index.mjs

[nodemon] 1.19.4
[nodemon] to restart at any time, enter `rs`
[nodemon] watching dir(s): *.*
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node --experimental-modules src/index.mjs`
(node:16942) ExperimentalWarning: The ESM module loader is experimental.
file:///home/joseph/placeholder2/main-server/src/games/game-player.mjs:3
export default class GamePlayer extends Player
                                        ^

ReferenceError: Cannot access 'Player' before initialization
    at file:///home/joseph/placeholder2/main-server/src/games/game-player.mjs:3:41
    at ModuleJob.run (internal/modules/esm/module_job.js:109:37)
    at async Loader.import (internal/modules/esm/loader.js:132:24)
[nodemon] app crashed - waiting for file changes before starting...

以下是 Player 文件(基类):

import PasswordHash from 'password-hash';

import GamesService from '../games/games.service.mjs';

import PlayersService from './players.service.mjs';

import QueueingService from '../queueing/queueing.service.mjs';

export default class Player
{
    constructor(object)
    {
        Object.assign(this, JSON.parse(JSON.stringify(object)));
    }

    get id()
    {
        return this._id.toString();
    }

    equals(other)
    {
        if(other.id != null)
            return other.id == this.id;
        return false;
    }

    checkPassword(password)
    {
        return PasswordHash.verify(password, this.password);
    }

    online()
    {
        return PlayersService.consumer.isPlayerOnline(this);
    }

    inQueue()
    {
        return QueueingService.queued(this);
    }

    inGame()
    {
        return GamesService.getActiveGameByPlayer(this) != null;
    }

    reduce()
    {
        return {
            id: this.id,
            username: this.username,
            email: this.email,
            admin: this.admin,
            online: this.online(),
            in_queue: this.inQueue(),
            in_game: this.inGame(),
        };
    }

    static hashPassword(password)
    {
        return PasswordHash.generate(password);
    }

    static schema = {
        username: String,
        password: String,
        email: String,
        email_confirmed: Boolean,
        admin: Boolean,
    }
}

和游戏玩家(子类):

import Player from '../players/player.mjs';

export default class GamePlayer extends Player
{
    constructor(player, token)
    {
        super(player);
        this.token = token;
    }
}

以及项目的层次结构:

src/
 -- games/
 --  -- game-player.mjs
 --  -- ...
    players/
 --  -- player.mjs
 --  -- ...
 -- ...

除非是其他原因，否则我该如何解决此导入问题？

编辑:据我所知，我没有使用 Babel，我正在使用 Node.js 提供的 --external-modules。不确定这是如何工作的。

Answer 1

我去了 Node.JS 论坛并询问可能是什么问题。根本不是 babel 问题，只是循环依赖。例如:

// A.js
import B from './B.js'
export default class A{}

// B.js
import A from './A.js'
export default class B extends A{}

抱歉，没有足够的信息来解决这个问题。我在 node.js github 上得到了很多帮助，有人在 github 上查看了我的项目，最终找到了一个两个模块相互指向的实例。