Develop Reference

Javascript Parse Date Contract_End_Date

I have Contract_End_Date 2 version : 2020-1-1 and 2020-1-11
Result will be like: 2020-01-01 or 2020-01-11
What is solution here?
var updates = {};
var removes = {};
let Contract_End_Date = '2020-1-11';
if (typeof Contract_End_Date !== 'undefined' && Contract_End_Date != null) {
var arr = Contract_End_Date.split(" ");
if (arr.length == 2) {
var firstPart = arr[0];
var dateParts = firstPart.split("-");
if (dateParts.length == 3) {
var day = parseInt(dateParts[2]);
if (day < 10) {
day = "0" + day;
}
var month = parseInt(dateParts[1]);
if (month < 10) {
month = "0" + month;
}
var year = dateParts[0];
updates["Contract_End_Date"] = year + "-" + month + "-" + day;
}
}
}
console.log(updates);

For working with dates in JS, I can just recommend "Moment.js".
It makes your code much more simple and readable.
In your case:
let Contract_End_Date = '2020-1-11';
let formattedDate = moment(Contract_End_Date, 'YYYY-MM-DD').format('YYYY-MM-DD');
console.log(formattedDate);
// 2020-01-11
For more information: https://momentjs.com/
EDIT: Since Moment.js won't get updated with the newest features, it may be better to use other libaries like Luxon

Count the number of anniversaries between two dates?

What is the easiest way in Javascript to calculate the number of anniversaries between two dates.
My attempt:
module.exports.countAnniversariesBetweenTwoDates = (start_date, end_date, anniversary_date) => {
if (start_date == end_date) {
return 0;
}
let start_date_year = start_date.getFullYear();
let end_date_year = end_date.getFullYear();
let anniversary_year = anniversary_date.getFullYear();
let start_date_month_and_day = Number(('0' + (start_date.getMonth() + 1)).slice(-2) + '' + ('0' + start_date.getDate()).slice(-2));
let end_date_month_and_day = Number(('0' + (end_date.getMonth() + 1)).slice(-2) + '' + ('0' + end_date.getDate()).slice(-2));
let anniversary_date_month_and_day = Number(('0' + (anniversary_date.getMonth() + 1)).slice(-2) + '' + ('0' + anniversary_date.getDate()).slice(-2));
let anniversary_count = 0;
// special case for start year
if (start_date_month_and_day < anniversary_date_month_and_day) {
anniversary_count++;
}
let temp_start_date_year = start_date_year + 1;
while(temp_start_date_year < end_date_year) {
anniversary_count++;
temp_start_date_year++;
}
// special case for end year
if (end_date_month_and_day > anniversary_date_month_and_day) {
anniversary_count++;
}
return anniversary_count;
}

Here's one that accounts for leap years:
function validDate(year, month, day) {
var testDate = new Date(year, month, day);
return testDate.getFullYear() === year && testDate.getMonth() === month && testDate.getDate() === day;
}
function countAnniversaries(begin, end, anniversary) {
var countDate = new Date(anniversary.getTime());
var anniversaries = 0;
var countYear = begin.getFullYear();
var anniversaryMonth = anniversary.getMonth();
var anniversaryDay = anniversary.getDate();
countDate.setFullYear(countYear);
while (countDate.getTime() <= end.getTime()) {
if (validDate(countYear, anniversaryMonth, anniversaryDay) && countDate.getTime() >= begin.getTime()) {
anniversaries++;
}
countYear++;
countDate.setFullYear(countYear);
countDate.setMonth(anniversaryMonth);
countDate.setDate(anniversaryDay);
}
return anniversaries;
}
console.log(countAnniversaries(new Date('Feb 1, 2012'), new Date('Feb 4, 2026'), new Date('Feb 2, 2012')))
console.log(countAnniversaries(new Date('Feb 1, 2012'), new Date('Feb 4, 2026'), new Date('Feb 29, 2012')))

If you use moment.js you can just get the difference between two dates as years, the use Math.floor() to round down to the nearest full number of years:
yearDiff = Math.floor(moment(new Date(endDate)).diff(new Date(startDate),'years'));
Edit: The code above can be simplified a bit more:
yearDiff = moment(endDate).diff(startDate,'years');
You may have to write some additional code to handle time periods of less than a year, or some other special cases.
You could of course loop through the dates similar to how you do it:
var startDate = "03/08/2019";
var endDate = "01/01/2022";
var anniversary = "03/07/2015";
var anniversaryCount = 0;
var counterMoment = moment(startDate);
while (counterMoment.isSameOrBefore(endDate)) {
var anniversaryThisYear = moment(anniversary).year(counterMoment.year());
if (counterMoment.isSame(anniversaryThisYear)) {
anniversaryCount++;
}
counterMoment.add(1,'day');
}
alert("Number of anniversaries: "+anniversaryCount);
It all depends on what the end result is and how you plan to use the value.

How to check conditions for every day of a year in loop?

I got lot of selected data from fullcalendar. I need to get those selected date from one whole year. How to check that in for loop?
I tried few answers to add days one by one to my condition from some answers ,but its not working for me.
Here is my code I tried:
var t=$(#dttbl).datatable();
var arr = new Array();
var date = new Date(),
var Id = 1;
var d = date.getDate(),
month = date.getMonth(),
year = date.getFullYear()
var day1 = y + '-01-01';
var day365 = y + '-12-31';
for (i = day1; i < day365; day1.setdate(day1.getdate() + 1)) {
if (($(i.cell).css('backgroundColor', 'blue'))) {
arr.push(([Id,i,'test']));
Id++;
}
}
for (i = 0; i < arr.length; i++) {
t.row.add([
arr[i][0],
arr[i][1],
arr[i][2]
]).draw();
}
I tried this getdate(), day1.add(1).day(); , day1=moment(day1).add(1, 'days') to add one by one day to check my condition for full year? These are not working for me. Is there any other way to do it?

You can use the following as #mplungjan commented.
var arr = [];
var date = new Date('01-01-2019');
var DAY = 1000 * 60 * 60 * 24;
var day1 = date.getTime();
var day365 = day1+ 365*DAY;
var iDay = day1;
while(iDay < day365){
// pushing the value in arr for example.
arr.push(new Date(iDay));
// do your logic
iDay = iDay + DAY;
}

You can use daysInMonth function of moment.js to find how many days in each month. After that you can create your array.
var dates = [];
var year = new Date().getFullYear();
for (var i = 1, l = 12; i <= l; i++){
var daysInMonth = moment("2012-" + i, "YYYY-M").daysInMonth();
console.log("month : " + i)
console.log("days in month : " + daysInMonth)
for (i1 = 1, l1 = daysInMonth; i1 <= l1; i1++) {
dates.push(year + "-" + i + "-" + i1)
}
}
console.log(dates);

How to I set a date to ISOString for different conditions

I'm trying to set a date in future based on different condition and then convert the date into string using the ISOString method. This is an example of the code;
<input type="text" name="unknown" id="dater" />
<p id="show"></p>
<button id="but">Show Date</button>
Having the script:
var text = document.getElementById("dater");
var date = new Date();
var n = date.setDate(date.getDate() + 12);
var x = date.toISOString()
var y = x.slice(0, -14);
document.getElementById("show").innerHTML = y;
Result:
2018-05-27
The output is based on today's date which is "2018-05-15". Now I want to set different date based on different conditions. I tried the following:
var pres = document.getElementById("but").addEventListener("click", now)
function now() {
var text = document.getElementById("dater");
var date = new Date();
var n = date.setDate(date.getDate() + 12);
var x = date.toISOString()
var y = x.slice(0, -14);
if(text.value == 5) { n = date.setDate(date.getDate() + 15)
} else if(text.value == 12) { n = date.setDate(date.getDate() + 22)
} else { n = date.setDate(date.getDate() + 3) }
document.getElementById("show").innerHTML = y;
}
if i input 5, 12 or 3 in the text field, nothing happens when I click the button. It just returns the same date "2018-05-27". However, if i say
document.getElementById("show").innerHTML = n;
or
document.getElementById("show").innerHTML = n.toISOString();
It returns the date in milliseconds.

I think this code will help you. you are not converting your variable in to Date object.
window.onload = function () {
var pres = document.getElementById("but").addEventListener("click", now);
}
function now() {
var text = document.getElementById("dater");
var date = new Date();
var n = date.setDate(date.getDate() + 12);
var x = date.toISOString()
var y = x.slice(0, -14);
if (text.value == 5) {
n = date.setDate(date.getDate() + 15)
} else if (text.value == 12) {
n = date.setDate(date.getDate() + 22)
} else { n = date.setDate(date.getDate() + 3) }
document.getElementById("show").innerHTML = new Date(n).toISOString();
}

JavaScript: get all months between two dates?

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 strings like this:
var dates = ['2012-04-01', '2012-05-01', '2012-06-01' .... '2014-11-01',];
So far this is what I've got, but it's pretty ugly:
var startDate = '2012-04-01';
var endDate = '2014-11-01';
var start = new Date(Date.parse(startDate));
var end = new Date(Date.parse(endDate))
var dates = [];
for (var i = start.getFullYear(); i < end.getFullYear() + 1; i++) {
dates.push(i + '-' + '-01');
}
console.log(dates);
Is there a better way? JSFiddle.

This should produce the desired output:
function dateRange(startDate, endDate) {
var start = startDate.split('-');
var end = endDate.split('-');
var startYear = parseInt(start[0]);
var endYear = parseInt(end[0]);
var dates = [];
for(var i = startYear; i <= endYear; i++) {
var endMonth = i != endYear ? 11 : parseInt(end[1]) - 1;
var startMon = i === startYear ? parseInt(start[1])-1 : 0;
for(var j = startMon; j <= endMonth; j = j > 12 ? j % 12 || 11 : j+1) {
var month = j+1;
var displayMonth = month < 10 ? '0'+month : month;
dates.push([i, displayMonth, '01'].join('-'));
}
}
return dates;
}
Just call it with your existing date format:
dateRange('2013-11-01', '2014-06-01')
// ["2013-11-01", "2013-12-01", "2014-01-01", "2014-02-01", "2014-03-01", "2014-04-01", "2014-05-01", "2014-06-01", "2014-07-01", "2014-08-01", "2014-09-01", "2014-10-01", "2014-11-01", "2014-12-01"]

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

If loading an extra library isn't a problem, you could always try the awesome MomentJS.
Gives for very clean and powerful date manipulation.
var startDate = moment('2012-04-01');
var endDate = moment('2014-11-01');
var dates = [];
endDate.subtract(1, "month"); //Substract one month to exclude endDate itself
var month = moment(startDate); //clone the startDate
while( month < endDate ) {
month.add(1, "month");
dates.push(month.format('YYYY-MM-DD'));
}
console.log(dates);
JSFiddle here

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 monthNum = year === fromYear ? fromMonth : 0;
const monthLimit = year === toYear ? toMonth : 11;
for(; monthNum <= monthLimit; monthNum++) {
let month = monthNum + 1;
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/

You are handling "logical" jumps, so you doesn't actually need timing arthmetics. So this is a simple counting problem:
var startDate = '2012-04-01';
var endDate = '2014-11-01';
var dates = [];
var d0 = startDate.split('-');
var d1 = endDate.split('-');
for (
var y = d0[0];
y <= d1[0];
y++
) {
for (
var m = d0[1];
m <= 12;
m++
) {
dates.push(y+"-"+m+"-1");
if (y >= d1[0] && m >= d1[1]) break;
};
d0[1] = 1;
};
console.log(dates);

Here is a solution which just uses string manipulation on that specific YYYY-MM-DD format:
function monthsBetween(...args) {
let [a, b] = args.map(arg => arg.split("-").slice(0, 2)
.reduce((y, m) => m - 1 + y * 12));
return Array.from({length: b - a + 1}, _ => a++)
.map(m => ~~(m / 12) + "-" + ("0" + (m % 12 + 1)).slice(-2) + "-01");
}
console.log(monthsBetween('2012-04-01', '2014-11-01'));

Here is another solution, using Date objects:
const enumerateMonths = (from, to) => {
const current = new Date(from)
current.setUTCDate(1)
current.setUTCHours(0, 0, 0, 0)
const toDate = new Date(to)
const months = []
while (current.getTime() <= toDate.getTime()) {
months.push(current.getUTCFullYear() + "-" + `${current.getUTCMonth() + 1}`.padStart(2, "0"))
current.setUTCMonth(current.getUTCMonth() + 1)
}
return months
}
This solution presumes you provide Date objects or ISO 8601 strings. Please mind that an ISO 8601 date does not necessarily have to contain the hours-minutes-seconds part. "2012-01-14" is a valid ISO 8601 date.

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;
};

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

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/

This is my solution, with help of math and O(n)
determineMonthInInterval(startDate, endDate) {
let startYear = startDate.getFullYear();
let endYear = endDate.getFullYear();
let startMonth = startDate.getMonth() + 1;
let endMonth = endDate.getMonth() + 1;
let monthAmount = (endMonth - startMonth) + 1 + (12 * (endYear - startYear));
let dates = [];
let currMonth = startMonth;
let currYear = startYear;
for( let i=0; i<monthAmount; i++){
let date = new Date(currYear + "/"+currMonth+"/1");
dates.push(date);
currYear = startYear + Math.floor((startMonth+i) / 12);
currMonth = (currMonth) % 12 +1;
}
return dates;
}

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;
}