ES6 singleton pattern: constructor returns an instance scoped to the module. With using the `new` operator.

es6-singleton-module-scoped-instance.js

let instance;

class Singleton {
  constructor() {
    if (!instance) {
      instance = this;
    }

    this._type = 'Singleton';
    return instance;
  }

  singletonMethod() {
    return 'singletonMethod';
  }

  static staticMethod() {
    return 'staticMethod';
  }

  get type() {
    return this._type;
  }

  set type(value) {
    this._type = value;
  }
}

export default Singleton;

// index.js
import Singleton from './Singleton';

// Instantiate
const instance2 = new Singleton();
console.log(instance2.type, instance2.singletonMethod());

// Getter/Setter
instance2.type = 'type updated';
console.log(instance2.type);

// Static method
console.log(Singleton.staticMethod());