lab-chronometer-solution.js

class Chronometer {
  constructor() {
    this.currentTime = 0;
    this.intervalId = null;
  }

  start(callback) {
    this.intervalId = setInterval(() => {
      this.currentTime++;
      if (callback) callback();
    }, 1000);
  }

  getMinutes() {
    return Math.floor(this.currentTime / 60);
  }

  getSeconds() {
    return this.currentTime % 60;
  }

  computeTwoDigitNumber(value) {
    return value < 10 ? '0' + value : String(value);
  }

  stop() {
    clearInterval(this.intervalId);
  }

  reset() {
    this.currentTime = 0;
  }

  split() {
    const minutes = this.computeTwoDigitNumber(this.getMinutes());
    const seconds = this.computeTwoDigitNumber(this.getSeconds());
    return `${minutes}:${seconds}`;
  }
}

// The following is required for our automated tests, ignore it for now.
if (typeof module !== 'undefined') module.exports = Chronometer;