How To Get List Of Days For Last Month, Last Three Months In MomentJS

Using moment().subtract(1, 'days').format('YYYY-MM-DD') i can get last x days from the current date. So how can i get all days from last month or last three months..?

Solution 1:

This is how to get the number of days in current month:

const numberOfDaysInCurrentMonth = moment().daysInMonth();

So this is how you can get the number of days for the last month:

const numberOfDaysInLastMonth = moment().subtract(1, 'months').daysInMonth();

Now you need the start of last month:

const startOfLastMonth = moment().subtract(1, 'months').startOf('month');

And you are ready to start iterating and build your list:

const numberOfDaysInLastMonth = moment().subtract(1, 'months').daysInMonth();
const startOfLastMonth = moment().subtract(1, 'months').startOf('month');

for (let i = 0; i < numberOfDaysInLastMonth; i = i + 1) {
  console.log(startOfLastMonth.format('YYYY MMM DD'));
  startOfLastMonth.add(1, 'days');
}

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For the last 3 months, just change you start date and number of Days:

const numberOfDaysInLast3Months = moment().subtract(1, 'months').daysInMonth() +
  moment().subtract(2, 'months').daysInMonth() +
  moment().subtract(3, 'months').daysInMonth();
const startDate = moment().subtract(3, 'months').startOf('month');

for (let i = 0; i < numberOfDaysInLast3Months; i = i + 1) {
  console.log(startDate.format('YYYY MMM DD'));
  startDate.add(1, 'days');
}

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Solution 2:

If I understand your question correctly, this can be achieved via two steps. First calculate the moment that marks the starting date of the prior month:

var prevMonth = moment().subtract(1, 'month').startOf('month');
var prevMonthDays = prevMonth.daysInMonth();

Then, iterate over the range 0...prevMonthDays, caclulating dates per day of that range, relative to the start of the previous month prevMonth:

  var prevMonthDay = prevMonth.clone().add(i, 'days').format("YYYY-MM-DD");

Something like this should achieve what you require:

// Get moment at start date of previous month
var prevMonth = moment().subtract(1, 'month').startOf('month');
var prevMonthDays = prevMonth.daysInMonth();

// Array to collect dates of previous month
var prevMonthDates = [];

for (var i = 0; i < prevMonthDays; i++) {

  // Calculate moment based on start of previous month, plus day offset
  var prevMonthDay = prevMonth.clone().add(i, 'days').format("YYYY-MM-DD");
  
  prevMonthDates.push(prevMonthDay);
}

console.log(prevMonthDates)

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Hope this helps!

Update

To calculate the list of dates starting many month past through to the beginning of the current month, the code above can be generalized as follows:

var monthsPast = 4;
var prevMonthDays = 0;
var prevMonth = moment();

// Iterate over number of months past that we want to collect dates for
for (var i = 0; i < monthsPast; i++) {

  // Calculate the moment at the start of a previous month
  var prevMonthStart = moment().subtract(i + 1, 'month').startOf('month');
  
  // Increment total range to collect dates over, and update prevMonth
  // to current calculated moment which represents oldest month start
  prevMonthDays += prevMonthStart.daysInMonth();
  prevMonth = prevMonthStart;
}

// Array to collect dates of previous month
var prevMonthDates = [];

for (var i = 0; i < prevMonthDays; i++) {

  // Calculate moment based on start of previous month, plus day offset
  var prevMonthDay = prevMonth.clone().add(i, 'days').format("YYYY-MM-DD");
  
  prevMonthDates.push(prevMonthDay);
}

console.log(prevMonthDates)

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