Performance logging in Typescript

dates.ts

      const dates = []
      const logDates = () => dates.forEach((datePair, index) => {
        if (index === 0) {
          console.debug(datePair[0], datePair[1])
        } else {
          console.debug(datePair[0], datePair[1], 'elapsed: ' + (datePair[1] - dates[index - 1][1]))
        }
        if (index === dates.length - 1) {
          console.debug('total', 'elapsed: ' + (datePair[1] - dates[0][1]))
        }
      })

      dates.push(['enter', Date.now()])