ObjectSingleton.js

const ObjectSingleton = {
  _instance: null,
  get instance() {
    if (!this._instance) {
      this._instance = {
        singletonMethod() {
          return 'singletonMethod';
        },

        _type: 'ObjectSingleton',

        get type() {
          return this._type;
        },

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

export default ObjectSingleton;

// Flux store way
export const ObjectSingletonAssign = Object.assign({}, {
  singletonMethod() {
    return 'singletonMethod';
  },

  _type: 'ObjectSingletonAssign',

  get type() {
    return this._type;
  },

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

// index.js
import ObjectSingleton, { ObjectSingletonAssign } from './ObjectSingleton';

// Instance
const instance = ObjectSingleton.instance;

// Prototype Method
console.log(instance.type, instance.singletonMethod());

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

/*
Flux
*/
// Prototype Method
console.log(ObjectSingletonAssign.type, ObjectSingletonAssign.singletonMethod());

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