// Singleton example for a Configuration Manager
class ConfigurationManager {
  constructor() {
    if (ConfigurationManager.instance) {
      return ConfigurationManager.instance;
    }
    // Initialize configuration here
    this.config = {
      language: 'en',
      theme: 'light'
    };
    ConfigurationManager.instance = this;
    return this;
  }

  getConfig() {
    return this.config;
  }

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

// Usage
const configManager1 = new ConfigurationManager();
const configManager2 = new ConfigurationManager();

console.log(configManager1 === configManager2); // true (same instance)

configManager1.setConfig({ language: 'fr', theme: 'dark' });
console.log(configManager2.getConfig()); // { language: 'fr', theme: 'dark' }