learning-design-patterns-singleton-logger.js

class Logger {
  sucesso(message) {
    console.log(`SUCESSO: ${message}`)
  }

  error(message) {
    console.error(`ERROR: ${message}`)
  }
}

class SingletonLogger {
  static _instance

  static _createInstance() {
    const logger = new Logger()
    return logger
  }

  static getInstance() {
    if (!this._instance) {
      this._instance = this._createInstance()
    }

    return this._instance
  }
}

const instance1 = SingletonLogger.getInstance()
const instance2 = SingletonLogger.getInstance()

console.log(instance1 === instance2)
// => true