[removed] get all months between two dates?

Question

I have two date strings like this:

var startDate = \'2012-04-01\';
var endDate = \'2014-11-01\';

And I want to end up with an array of stri

Answer 1

  const getMonths = (fromDate, toDate) => {
    const fromYear = fromDate.getFullYear();
    const fromMonth = fromDate.getMonth();
    const toYear = toDate.getFullYear();
    const toMonth = toDate.getMonth();
    const months = [];
    for(let year = fromYear; year <= toYear; year++) {
      let month = year === fromYear ? fromMonth : 0;
      const monthLimit = year === toYear ? toMonth : 11;
      for(; month <= monthLimit; month++) {
        months.push({ year, month })
      }
    }
    return months;
  }
const sample = getMonths(new Date('2022-07-28'), new Date('2023-03-20'));
console.log(sample);
document.write('check the console output');

https://jsfiddle.net/xfayoqvs/

Answer 2

Still not a very elegant answer, but arrives at the array of strings you want:

var startDate = '2012-04-01';
var endDate = '2014-11-01';
var start = new Date(startDate);
var end = new Date(endDate);
var dates = [];
for (var i = start.getFullYear(); i < end.getFullYear() + 1; i++) {
    for (var j = 1; j <= 12; j++) {
      if (i === end.getFullYear() && j === end.getMonth() + 3) {
        break;
      }
      else if (i === 2012 && j < 4){
        continue;
      }
      else if (j < 10) {
        var dateString = [i, '-', '0' + j, '-','01'].join('');
        dates.push(dateString)
        }
      else {
        var dateString = [i, '-', j, '-','01'].join('');
        dates.push(dateString);
        }
    }
}
console.log(dates);

jsfiddle link here: http://jsfiddle.net/8kut035a/

Answer 3

Here is another option:

getRangeOfMonths(startDate: Date, endDate: Date) {
    const dates = new Array<string>();
    const dateCounter = new Date(startDate);
    // avoids edge case where last month is skipped
    dateCounter.setDate(1);
    while (dateCounter < endDate) {
      dates.push(`${dateCounter.getFullYear()}-${dateCounter.getMonth() + 1}`);
      dateCounter.setMonth(dateCounter.getMonth() + 1);
    }
    return dates;
  }

Answer 4

All solutions above run in O(n^2) time complexity, which is not very efficient. See below solution in O(n) time complexity:

function getAllMonths(start, end){	
	let startDate = new Date(start);
	let startYear = startDate.getFullYear();
	let startMonth = startDate.getMonth()+1;
	
	let endDate = new Date(end);
	let endYear = endDate.getFullYear();
	let endMonth = endDate.getMonth()+1;
	
	let countMonth = 0;
	let countYear = 0;
	let finalResult = [];

	for(let a=startYear; a<=endYear; a++){

		if(startYear<endYear){
			if(countYear==0){
				countMonth += 12-startMonth;
            }else 
			if(countYear>0){
				countMonth += 12;
            }
			countYear+=1;
			startYear++;
        }else 
		if(startYear==endYear){
			countMonth+=endMonth;
        }
    }
	for(let i=startMonth; i<=countMonth+startMonth; i++){
		finalResult.push(startDate.getFullYear()+(Math.floor(i/12)) + "-" + Math.round(i%13) + "-" + "01");
    }
	return finalResult;
}

getAllMonths('2016-04-01', '2018-01-01');

Might share a much more simpler code

Answer 5

An example to get all first days of months between a given date and now using moment.js.

   var getMonths = function (startDate) {
    var dates = [];
    for (var year = startDate.year(); year <= moment().year(); year++) {
        var endMonth = year != moment().year() ? 11 : moment().month();
        var startMonth = year === startDate.year() ? startDate.month() : 0;
        for (var currentMonth = startMonth; currentMonth <= endMonth; currentMonth = currentMonth > 12 ? currentMonth % 12 || 11 : currentMonth + 1) {
            var month = currentMonth + 1;
            var displayMonth = month < 10 ? '0' + month : month;
            dates.push([year, displayMonth, '01'].join('-'));
        }
    }
    return dates;
};

Answer 6

You can also use the excellent moment.js library:

var startDate = moment('2012-04-01');
var endDate = moment('2014-11-01');

var result = [];

if (endDate.isBefore(startDate)) {
    throw "End date must be greated than start date."
}      

while (startDate.isBefore(endDate)) {
    result.push(startDate.format("YYYY-MM-01"));
    startDate.add(1, 'month');
}

JSFiddle