timer.js

const timer  = [];

module.exports = {
  step:  (key) => {
    timer.push({
      key:  key,
      time: new Date().getTime()
    });
  },
  view:  () => {
    const result = [];
    let total    = 0;

    for (let i = 0, len = timer.length; i < len; i++) {
      if (i === 0) {
        result.push(timer[0].key + ' - ' + 0);
      } else {
        result.push(timer[i].key + ' - ' + (timer[i].time - timer[i - 1].time));
        total += timer[i].time - timer[i - 1].time;
      }
    }
    result.push('Total - ' + total);
    return result;
  },
  reset: () => {
    timer.splice(0, timer.length);
  }
};