Singleton Pattern in JavaScript?

Instead of my usual blog post, I'd like to pose a question.

How often do you JavaScript developers use singleton patterns?

If I wanted to implement a singleton pattern in ES6, is this how I'd do it?

If not, why not?

// notifications.js
class Notifications {

  constructor() {
    this.messages = [];
  }

  add(message) {
    this.messages.push(message);
  }
}

export const notifications = new Notifications();
// ☝️ asking about this

// main.js
// 👇 less important
import { notifications } from './notifications';

class Main {
  constructor() {
    notifcations.add('some message')
  }
}

new Main();

Comments

[Rudy Nappée]

Not sure you can have a private constructor in js...

That said, you don't really need singletons in JS... Using functions inside es6 modules do the exact same job (you can even store a state inside modules).

[Pacharapol Withayasakpunt]

You can have a private constructor in TypeScript. But all is lost when transpiled down to JavaScript.

[pentacular]

l would separate the class definition and the shared instances, putting them in different modules.

Then you can have as many "singletons" as you need.