Modified Ticker

index.mjs

// 3.3 A simple modification: Modify the function created in exercise 3.2 so that
// it emits a tick event immediately after the function is invoked.

import EventEmitter from 'events';

function ticker(number, cb) {
  const eventEmitter = new EventEmitter();

  // Next tick is needed preventing to unleash Zalgo
  process.nextTick(() => {
    eventEmitter.emit('tick');
  });

  let tickCount = 0;

  eventEmitter.on('tick', () => {
    tickCount++;
  });

  const timer = function (totalMs) {
    setTimeout(() => {
      eventEmitter.emit('tick');

      if (totalMs <= 0) {
        return cb(tickCount);
      }

      timer(totalMs - 50);
    }, 50);
  };

  timer(number);

  return eventEmitter;
}

ticker(1000, (tickCount) => console.log(`Tick count: `, tickCount)).on('tick', () => console.log('A tick is passed'));