Observer & Singleton Patterns

What are the best practices for implementing a Singleton in a module system?

// singleton.js
let instance = null;

export class ModuleSingleton {
  constructor() {
    if (instance) {
      return instance;
    }
    instance = this;
    this.initialize();
  }

  initialize() {
    this.config = {};
  }
}

export const getInstance = () => {
  if (!instance) {
    instance = new ModuleSingleton();
  }
  return instance;
};

// Usage:
// import { getInstance } from './singleton.js';
// const singleton = getInstance();

Export multiple instances
Use global variables
Export instance getter and class separately
This implementation shows best practices for module-based Singletons by: 1) Leveraging module scope to maintain instance privacy, 2) Providing a clear getInstance function for access, 3) Exporting both the class and getter for flexibility, and 4) Ensuring consistent instance access across imports. This approach works well with modern JavaScript module systems while maintaining singleton behavior.
Create new instance on every import

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