function hrTimeDurationInMs(startTime, endTime) {
    if (!Array.isArray(startTime) || !Array.isArray(endTime)) {
        return null;
    }

    var secondDiff = endTime[0] - startTime[0];
    var nanoSecondDiff = endTime[1] - startTime[1];
    var diffInNanoSecond = secondDiff * NS_PER_SEC + nanoSecondDiff;

    return Math.round(diffInNanoSecond / MS_PER_NS);
}
Get duration in milliseconds from two process.hrtime()
@function hrTimeDurationInMs
@param {Array} startTime - [seconds, nanoseconds]
@param {Array} endTime - [seconds, nanoseconds]
@returns {Number|null} durationInMs