How to apply singleton pattern in node.js?

Question

Node.js

How to apply singleton pattern in node.js in different files without using global object?

App structure
app/app.js
app/files/Shop.js
app/files/Fruits.js

app.js

let Shop = require("./files/Shop");
let shop = new Shop();

Fruits.js

let Shop = require("./Shop");
let shop = Shop.getInstance(); // цель - получение ссылки на созданный экземпляр в app.js

Since the file is connected again, respectively, all those variables or static properties (Shop.instance) that are created in it to store a link to the instance are recreated.

Solution:

Shop.js

class Shop {
    constructor() {
        this._store = null;
    }

    setStore(value) {
        this._store = value;
    }

    getStore(value) {
        return this._store;
    }
}

module.exports = new Shop();

app.js

let shop = require("./files/Shop");

shop.setStore("apple");

Fruits.js

let shop = require("./Shop");

shop.getStore(); // "apple"

Answer 1

You don't show anywhere how you do the export.
By themselves, CommonJS modules already implement Singleton.

// app/app.js
const Shop = require("./files/Shop");
const shop = new Shop();

module.exports = shop;

// app/files/Fruits.js
const shop = require('../app'); // shop, созданный в app.js, будет всегда один и тот же

When including the file require('../app'); again, the same shop will be obtained.
If you want to get shop from the Shop module, then you can create it once there and export it.