chronometer.js

class Chronometer {
  constructor() {
    // ... your code goes here
    this.currentTime = 0;
    this.intervalId = null;
  }

  start(callback) {
    // ... your code goes here
    this.intervalId = setInterval(() => {
      this.currentTime++;

      if (callback) {
        callback();
      }
    }, 1000);
  }

  getMinutes() {
    // ... your code goes here
    const minutes = Math.floor(this.currentTime / 60);
    return minutes;
  }

  getSeconds() {
    // ... your code goes here
    const seconds = this.currentTime % 60;
    return seconds;
  }

  computeTwoDigitNumber(value) {
    // ... your code goes here
    var formattedNumber = ('0' + value).slice(-2);
    const val = formattedNumber.toString();
    return val;
  }

  stop() {
    // ... your code goes here
    clearInterval(this.intervalId);
  }

  reset() {
    // ... your code goes here
    this.currentTime = 0;
  }

  split() {
    // ... your code goes here
    const minute = this.getMinutes();
    const minVal = this.computeTwoDigitNumber(minute);

    const second = this.getSeconds();
    const secVal = this.computeTwoDigitNumber(second);

    const formattedTime = `${minVal}:${secVal}`;

    return formattedTime;
  }
}

// The following is required to make unit tests work.
/* Environment setup. Do not modify the below code. */
if (typeof module !== 'undefined') {
  module.exports = Chronometer;
}