oneTimestampPerHour.js

module.exports = {

  // given an array of timestamps only, returns a set of relevant timestamps
  // to previous hours, only allowing one timestamp per hour
  hourlyTimestamps: function (array){
    const now = new Date().getTime();
    let msh = 3.6e+6; // milliseconds per hour
    let hoursGone = 0;
    let theseHours = []; // array of representative data on an hourly basis, 0 if no data
    let analysisDuration = 168; // hours in a given week.
    let calc = [];
    for (let i = 0; i < analysisDuration; i++) {
      const lastHour = now - hoursGone; // iterated hour. new entries must be > lastHour - msh
      let found = false;
      for (let j = 0; j < array.length; j++) {

        if (array[j] <= lastHour && array[j] > lastHour - msh && !found) {
          theseHours[i] = array[j]; // add most recent only
          calc[i] = {l: lastHour, ts: array[j], d: lastHour - msh};
          found = true;
        }
      }
      if (!found) {
        calc[i] = {l: lastHour, ts: 0, d: lastHour - msh};
        theseHours[i] = 0;
      }
      hoursGone += msh;
    }
    return ({set: theseHours, audit: calc})
  }
};