Exemplo DEPOIS da refatoração do artigo Design Patterns: Null Object.

design-pattern-null-object-article-example-after.ts

class NullLogger implements Logger {
  warn(message: string): void {
  }
}

class LoggerFactory {
  factory(env: string): Logger {
    if (env === 'development') {
      return new ConsoleLogger();
    }

    return new NullLogger();
  }
}

class Client {
  execute() {
    const logger = (new LoggerFactory()).factory('production');

    logger.warn('It\'s on fire, bicho');
  }
}