di-for-effects.ts

interface ILogger {
  log: (str: string) => void;
}

class Logger implements ILogger {
  log = (str: string): void => {
    console.log(str);
  };
}

class MyBusinessClass {
  constructor(private logger: Logger) {}

  addEffectful = (a: number, b: number): number => {
    this.logger.log(a.toString());
    this.logger.log(b.toString());
    return a + b;
  };
}

const logger = new Logger();
const business = new MyBusinessClass(logger);
const result = business.addEffectful(1, 2);
console.log(`result: ${result}`);