Given an ISO date, get the days of the week in form of ISO string ranges

Question

Suppose I have an ISO date, such as 2021-09-18T20:18:27.000Z

1. I would like to get the dates of the past week in form of an array
2. The array should be a set of arrays that have two ISO dates that represent the start of the day and the end of the day as illustrated below:

E.g.

input:

2021-09-18T20:18:27.000Z

output:

[
['"2021-09-11T00:00:00.000Z', '"2021-09-11T23:59:59.000Z'],
['"2021-09-12T00:00:00.000Z', '"2021-09-11T23:59:59.000Z'],
['"2021-09-13T00:00:00.000Z', '"2021-09-11T23:59:59.000Z'],
['"2021-09-14T00:00:00.000Z', '"2021-09-11T23:59:59.000Z'],
['"2021-09-15T00:00:00.000Z', '"2021-09-11T23:59:59.000Z'],
['"2021-09-16T00:00:00.000Z', '"2021-09-11T23:59:59.000Z'],
['"2021-09-17T00:00:00.000Z', '"2021-09-11T23:59:59.000Z'],
['"2021-09-18T00:00:00.000Z', '"2021-09-18T23:59:59.000Z'],
]

I've already tried it with dayjs, this results in the array representing exact intervals from a particular date:

function getDates(date) {
  var dates = [date]
  var noOfDays = 7

  for (let i = noOfDays - 1; i >= 0; i--) {
    const elementIndex = i - noOfDays // Get last nth element of the list
    const dateToIncrement = dates.slice(elementIndex)[0]
    const newDate = dayjs(dateToIncrement).subtract(1, "day").toISOString()
    dates.unshift(newDate)
  }
  return dates
}

Thank you

Answer 1

function getPastWeek(inputTime) {
    var res = []; //result array
    var currentDayEnd = undefined; //variable to be set on each iteration
    var currentDay = new Date(inputTime.split('T')[0]); //create new Date object
    currentDay.setDate(currentDay.getDate() - 7); //reduce seven days from current date

    for(var i = 0; i <= 7; i++) { //foreach day in last week
        currentDayEnd = new Date(currentDay.getTime() - 1000); //previous day end (1sec before current day start)
        currentDayEnd.setDate(currentDayEnd.getDate() + 1); //current day end (one day after previous day end)
        res.push([currentDay.toISOString(), currentDayEnd.toISOString()]); //append pair

        currentDay.setDate(currentDay.getDate() + 1); //set variable to next day
    }

    return res;
}

var pastWeek = getPastWeek('2021-09-18T20:18:27.000Z'); //call example

Answer 2

The OP code is pretty close, you should have been able to adapt it to your needs. The following employs a similar algorithm. End of day is set to 1ms before midnight.

// Given a UTC ISO 8601 timestamp, return array of day plus 
// previous 6 days with start of day, end of day timestmaps
function getDates(d) {
  let s = new Date(d.slice(0,10));
  let e = new Date(+s);
  e.setUTCHours(23,59,59,999);
  let result = [];

  for (let i=7; i; i--) {
    result.push([s.toISOString(), e.toISOString()]);
    s.setUTCDate(s.getUTCDate() - 1);
    e.setUTCDate(e.getUTCDate() - 1);
  }
  return result;
}

console.log(getDates(new Date().toISOString()));