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start week day from sunday - javascript

I want to retrieve a date by providing day number of a specific week
E.g
When I say
day: 1
It should provide me:
2023-01-15
What I have tried so far is:
function calculatedDate (day){
let date = new Date();
let dayAtDate = date.getDay();
let dayDiff = day - dayAtDate;
if(dayDiff < 0){
dayDiff = 7 + dayDiff;
}
let desiredDate = date.setDate(date.getDate() + dayDiff);
return new Date(desiredDate);
}
console.log(calculatedDate(1));
Now the problem with above code is that it considers day: 1 as monday, but I want day: 1 to be sunday here.
Can anyone help me with the best possible way here?

How about just -1 the provided day? that should solve it:
function calculatedDate (day){
let date = new Date();
let dayAtDate = date.getDay();
day = day - 1;
let dayDiff = day - dayAtDate;
if(dayDiff < 0){
dayDiff = 7 + dayDiff;
}
let desiredDate = date.setDate(date.getDate() + dayDiff);
return new Date(desiredDate);
}
console.log(calculatedDate(1));
You'd probably want to add some validation on the input parameter day, make sure it's a number and 1 or greater.

The current day will be 0, account for this by making the following change.
if(dayDiff < 0){
dayDiff = 6 + dayDiff;
}

Sunday is 0, Monday is 1 here :
function calculatedDate (day) {
let date = new Date();
let dayAtDate = date.getDay();
let dayDiff = day - (dayAtDate + 1); // change here
if (dayDiff < 0) {
dayDiff = 7 + dayDiff;
}
let desiredDate = date.setDate(date.getDate() + dayDiff);
return new Date(desiredDate);
}
console.log(calculatedDate(1));

Calendar to show today's current date with the next 60 days

I have created a calendar that successfully displays todays current date. It also shows the remaining months however I am trying to change the functionality of the calendar so that it only shows the next 60 days from today's current date.
The code so far:
var todayDate = new Date();
var finalDate = new Date(todayDate)
finalDate.setDate(todayDate.getDate() + 60)
var dayNumber = todayDate.getDate();
var month = todayDate.getMonth();
var year = todayDate.getFullYear();
var months = ["January","February","March","April","May","June","July","August","September","October","November","December"];
var calendarTable = document.getElementById("calendar-body");
document.getElementById("month").innerHTML = months[month];
document.getElementById("year").innerHTML = year;
function createCalendar(month, year) {
var firstDay = new Date(year, month).getDay();
var totalDays = daysInMonth(month, year);
blankDates(firstDay);
for (var day = 1; day <= totalDays; day++) {
var cell = document.createElement("li");
var cellText = document.createTextNode(day);
if (
dayNumber === day &&
month === todayDate.getMonth() &&
year === todayDate.getFullYear()
) {
cell.classList.add("todays-day");
}
cell.setAttribute("data-day", day);
cell.setAttribute("data-month", month);
cell.setAttribute("data-year", year);
cell.classList.add("singleDay");
cell.appendChild(cellText);
calendarTable.appendChild(cell);
}
}
function daysInMonth(month, year) {
return new Date(year, month + 1, 0).getDate();
}
function blankDates(count) {
for (var x = 0; x < count; x++) {
var cell = document.createElement("li");
var cellText = document.createTextNode("");
cell.appendChild(cellText);
calendarTable.appendChild(cell);
}
}
createCalendar(month, year);
Any ideas would be great. Thanks :)

First you need to find the number of dates between two dates,
In this case is finalDate and todayDate
var diff = Math.floor(( Date.parse(finalDate) - Date.parse(todayDate)) / 86400000);
You get the difference days (or NaN if one or both could not be parsed). The parse date gived the result in milliseconds and to get it by day you have to divided it by 24 * 60 * 60 * 1000
The output of the diff now is 60
Then you add the diff variable into the for loop.
Woking example

Just an idea.
But you could generate an array of the dates between now and 60 days.
Then loop through that array to build the calendar.
This way the Date functions can be used for each date in the array.
Here's a simple function to generate such array.
function getDateRange(pStartDate, pDays) {
let days = pDays || 1;
let dates = [];
let n = 0;
let startDate = new Date(pStartDate.toISOString().slice(0,10));
let endDate = new Date(startDate.getTime() + (days * 86400000));
do {
dates.push(new Date(startDate.getTime() + (n * 86400000)));
n++;
} while (n <= days);
let obj = {
startDate : startDate,
endDate : endDate,
days : dates.length,
dates : dates
}
return obj;
}
var dateRange = getDateRange(new Date(), 60);
console.log(dateRange.dates);

Get end date from a given start date , weekdays and number of occuring of executions

I am new to programming. I am using javascript right now. I wanted codes to get end date for a execution. I have got Startdate, weekdays(days in which execution occures) and number of executions to occure. How can i get end date???
For example Start date is '15 - 03 - 2018'
days to be executed are Sunday ie '0' and friday '5'
Number of executions from start date to end date is 5
End date of execution here should be '30-03-2018' which is to be retrieved.
Any idea...

Hope this helps.
var date = new Date(2018,2,15); // set date to 15-Mar-2018
var weekdays = [0,6]; // set weekdays
var noOfExcution = 3;
var day = 7 - date.getDay(); //calculate first week days
noOfExcution -= weekdays.filter(x=>x>=date.getDay()).length;
day += noOfExcution % weekdays.length > 0
? weekdays[noOfExcution % weekdays.length - 1]
: weekdays[weekdays.length-1]; //calulate last week days
var x = Math.floor((noOfExcution-0.1) / weekdays.length) * 7 +
day; //calculate in between dates
date.setDate(date.getDate() + x); //setting end date
console.log(date.toLocaleString()); //printing end date

It can be done like this. I somehow figured out a method.
function calcDate() {
var type="weekly";
var date1=new Date('2018,mar,18');
var date2;
var gdays=[];
gdays[0]=0;
gdays[1]=1;
count=10;
if(type=="weekly"){
var d1=date1.getDate();
var year=date1.getFullYear();
var month=date1.getMonth();
while(count>0){
var temp=[];
var tempdays=[];
tempdays=getDaysInMonth(month,year,d1);
console.log(tempdays);
for(var i=0;i<=gdays.length-1;i++) {
var on=gdays[i];
var ddd=days(year,month,on);
for(var j=0;j<=ddd.length-1;j++){
temp.push(ddd[j]);
}
}
temp.sort(function(a, b){return a-b});
console.log(temp);
for(var k=0;k<=temp.length-1;k++){
if(tempdays.includes(temp[k])){
var finalday=temp[k];
count--;
alert("count" +count);
if(count==0) break;
}
}
if(count==0){
alert("final day"+finalday);
date2=new Date(year,month,finalday);
alert(date2);
}
if(count>0){
d1=0;
month=month+1;
if(month>11){
month=0;
year=year+1;
}
}
}
}
function days(year,month,on){
var day, counter, date;
var days=[];
day = 1;
counter = 0;
date = new Date(year, month, day);
while (date.getMonth() === month) {
if (date.getDay() ==on) { // Sun=0, Mon=1, Tue=2, etc.
days[counter]=date.getDate();
counter += 1;
}
day += 1;
date = new Date(year, month, day);
}
return(days);
}
function getDaysInMonth(month, year,day) {
day++;
alert(day);
var date = new Date(year, month, day);
var days = [];
while (date.getMonth() === month) {
var i=date.getDate();
days.push(i);
date.setDate(date.getDate()+1);
}
return days;
}
}

group by weeks,days and year javascript [duplicate]

I have today = new Date(); object. I need to get first and last day of the current week. I need both variants for Sunday and Monday as a start and end day of the week. I am little bit confuse now with a code. Can your help me?

var curr = new Date; // get current date
var first = curr.getDate() - curr.getDay(); // First day is the day of the month - the day of the week
var last = first + 6; // last day is the first day + 6
var firstday = new Date(curr.setDate(first)).toUTCString();
var lastday = new Date(curr.setDate(last)).toUTCString();
firstday
"Sun, 06 Mar 2011 12:25:40 GMT"
lastday
"Sat, 12 Mar 2011 12:25:40 GMT"
This works for firstday = sunday of this week and last day = saturday for this week. Extending it to run Monday to sunday is trivial.
Making it work with first and last days in different months is left as an exercise for the user

Be careful with the accepted answer, it does not set the time to 00:00:00 and 23:59:59, so you can have problems.
You can use a third party date library to deal with dates. For example:
var startOfWeek = moment().startOf('week').toDate();
var endOfWeek = moment().endOf('week').toDate();
EDIT: As of September 2020, using Moment is discouraged for new projects (blog post)
Another popular alternative is date-fns.

You can also use following lines of code to get first and last date of the week:
var curr = new Date;
var firstday = new Date(curr.setDate(curr.getDate() - curr.getDay()));
var lastday = new Date(curr.setDate(curr.getDate() - curr.getDay()+6));
Hope it will be useful..

The excellent (and immutable) date-fns library handles this most concisely:
const start = startOfWeek(date);
const end = endOfWeek(date);
Default start day of the week is Sunday (0), but it can be changed to Monday (1) like this:
const start = startOfWeek(date, {weekStartsOn: 1});
const end = endOfWeek(date, {weekStartsOn: 1});

Here's a quick way to get first and last day, for any start day.
knowing that:
1 day = 86,400,000 milliseconds.
JS dates values are in milliseconds
Recipe: figure out how many days you need to remove to get the your week's start day (multiply by 1 day's worth of milliseconds). All that is left after that is to add 6 days to get your end day.
var startDay = 1; //0=sunday, 1=monday etc.
var d = now.getDay(); //get the current day
var weekStart = new Date(now.valueOf() - (d<=0 ? 7-startDay:d-startDay)*86400000); //rewind to start day
var weekEnd = new Date(weekStart.valueOf() + 6*86400000); //add 6 days to get last day

Small change to #Chris Lang answer.
if you want Monday as the first day use this.
Date.prototype.GetFirstDayOfWeek = function() {
return (new Date(this.setDate(this.getDate() - this.getDay()+ (this.getDay() == 0 ? -6:1) )));
}
Date.prototype.GetLastDayOfWeek = function() {
return (new Date(this.setDate(this.getDate() - this.getDay() +7)));
}
var today = new Date();
alert(today.GetFirstDayOfWeek());
alert(today.GetLastDayOfWeek());
Thaks #Chris Lang

This works across year and month changes.
Date.prototype.GetFirstDayOfWeek = function() {
return (new Date(this.setDate(this.getDate() - this.getDay())));
}
Date.prototype.GetLastDayOfWeek = function() {
return (new Date(this.setDate(this.getDate() - this.getDay() +6)));
}
var today = new Date();
alert(today.GetFirstDayOfWeek());
alert(today.GetLastDayOfWeek());

You could do something like this
var today = new Date();
var startDay = 0;
var weekStart = new Date(today.getDate() - (7 + today.getDay() - startDay) % 7);
var weekEnd = new Date(today.getDate() + (7 - today.getDay() - startDay) % 7);
Where startDay is a number from 0 to 6 where 0 stands for Sunday (ie 1 = Monday, 2 = Tuesday, etc).

SetDate will sets the day of the month. Using setDate during start and end of the month,will result in wrong week
var curr = new Date("08-Jul-2014"); // get current date
var first = curr.getDate() - curr.getDay(); // First day is the day of the month - the day of the week
var last = first + 6; // last day is the first day + 6
var firstday = new Date(curr.setDate(first)); // 06-Jul-2014
var lastday = new Date(curr.setDate(last)); //12-Jul-2014
If u setting Date is 01-Jul-2014, it will show firstday as 29-Jun-2014 and lastday as 05-Jun-2014 instead of 05-Jul-2014
So overcome this issue i used
var curr = new Date();
day = curr.getDay();
firstday = new Date(curr.getTime() - 60*60*24* day*1000); //will return firstday (ie sunday) of the week
lastday = new Date(firstday.getTime() + 60 * 60 *24 * 6 * 1000); //adding (60*60*6*24*1000) means adding six days to the firstday which results in lastday (saturday) of the week

I recommend to use Moment.js for such cases. I had scenarios where I had to check current date time, this week, this month and this quarters date time. Above an answer helped me so I thought to share rest of the functions as well.
Simply to get current date time in specific format
case 'Today':
moment().format("DD/MM/YYYY h:mm A");
case 'This Week':
moment().endOf('isoweek').format("DD/MM/YYYY h:mm A");
Week starts from Sunday and ends on Saturday if we simply use 'week' as parameter for endOf function but to get Sunday as the end of the week we need to use 'isoweek'.
case 'This Month':
moment().endOf('month').format("DD/MM/YYYY h:mm A");
case 'This Quarter':
moment().endOf('quarter').format("DD/MM/YYYY h:mm A");
I chose this format as per my need. You can change the format according to your requirement.

//get start of week; QT
function _getStartOfWeek (date){
var iDayOfWeek = date.getDay();
var iDifference = date.getDate() - iDayOfWeek + (iDayOfWeek === 0 ? -6:1);
return new Date(date.setDate(iDifference));
},
function _getEndOfWeek(date){
return new Date(date.setDate(date.getDate() + (7 - date.getDay()) === 7 ? 0 : (7 - date.getDay()) ));
},
*current date == 30.06.2016 and monday is the first day in week.
It also works for different months and years.
Tested with qunit suite:
QUnit.module("Planung: Start of week");
QUnit.test("Should return start of week based on current date", function (assert) {
var startOfWeek = Planung._getStartOfWeek(new Date());
assert.ok( startOfWeek , "returned date: "+ startOfWeek);
});
QUnit.test("Should return start of week based on a sunday date", function (assert) {
var startOfWeek = Planung._getStartOfWeek(new Date("2016-07-03"));
assert.ok( startOfWeek , "returned date: "+ startOfWeek);
});
QUnit.test("Should return start of week based on a monday date", function (assert) {
var startOfWeek = Planung._getStartOfWeek(new Date("2016-06-27"));
assert.ok( startOfWeek , "returned date: "+ startOfWeek);
});
QUnit.module("Planung: End of week");
QUnit.test("Should return end of week based on current date", function (assert) {
var endOfWeek = Planung._getEndOfWeek(new Date());
assert.ok( endOfWeek , "returned date: "+ endOfWeek);
});
QUnit.test("Should return end of week based on sunday date with different month", function (assert) {
var endOfWeek = Planung._getEndOfWeek(new Date("2016-07-03"));
assert.ok( endOfWeek , "returned date: "+ endOfWeek);
});
QUnit.test("Should return end of week based on monday date with different month", function (assert) {
var endOfWeek = Planung._getEndOfWeek(new Date("2016-06-27"));
assert.ok( endOfWeek , "returned date: "+ endOfWeek);
});
QUnit.test("Should return end of week based on 01-06-2016 with different month", function (assert) {
var endOfWeek = Planung._getEndOfWeek(new Date("2016-06-01"));
assert.ok( endOfWeek , "returned date: "+ endOfWeek);
});
QUnit.test("Should return end of week based on 21-06-2016 with different month", function (assert) {
var endOfWeek = Planung._getEndOfWeek(new Date("2016-06-21"));
assert.ok( endOfWeek , "returned date: "+ endOfWeek);
});
QUnit.test("Should return end of week based on 28-12-2016 with different month and year", function (assert) {
var endOfWeek = Planung._getEndOfWeek(new Date("2016-12-28"));
assert.ok( endOfWeek , "returned date: "+ endOfWeek);
});
QUnit.test("Should return end of week based on 01-01-2016 with different month and year", function (assert) {
var endOfWeek = Planung._getEndOfWeek(new Date("2016-01-01"));
assert.ok( endOfWeek , "returned date: "+ endOfWeek);
});

var dt = new Date() //current date of week
var currentWeekDay = dt.getDay();
var lessDays = currentWeekDay == 0 ? 6 : currentWeekDay-1
var wkStart = new Date(new Date(dt).setDate(dt.getDate()- lessDays));
var wkEnd = new Date(new Date(wkStart).setDate(wkStart.getDate()+6));
This will be useful for any date scenario.

Just using pure javascript, you can use the function below to get first day and last day of a week with freely setting day for start of week.
var weekday = [];
weekday[0] = "Sunday";
weekday[1] = "Monday";
weekday[2] = "Tuesday";
weekday[3] = "Wednesday";
weekday[4] = "Thursday";
weekday[5] = "Friday";
weekday[6] = "Saturday";
function getFirstDayOfWeek(date, from) {
//Default start week from 'Sunday'. You can change it yourself.
from = from || 'Sunday';
var index = weekday.indexOf(from);
var start = index >= 0 ? index : 0;
var d = new Date(date);
var day = d.getDay();
var diff = d.getDate() - day + (start > day ? start - 7 : start);
d.setDate(diff);
return d;
};
Last day of week is just 6 days after first day of week
function getLastDayOfWeek(date, from) {
from = from || 'Sunday';
var index = weekday.indexOf(from);
var start = index >= 0 ? index : 0;
var d = new Date(date);
var day = d.getDay();
var diff = d.getDate() - day + (start > day ? start - 1 : 6 + start);
d.setDate(diff);
return d;
};
Test:
getFirstDayOfWeek('2017-10-16'); //--> Sun Oct 15 2017
getFirstDayOfWeek('2017-10-16', 'Monday'); //--> Mon Oct 16 2017
getFirstDayOfWeek('2017-10-16', 'Tuesday'); //--> Tue Oct 10 2017

The biggest issue when the given date's week is in-between two months. (Like 2022-07-01, it's the 5th day of the week.)
Using getDay function we check if the week is in-between months.
Note: getDay() function identifies week start day as sunday, so it'll return 0 for sunday.
var curr = new Date(); // get current date
var weekdaynum = curr.getDay();
if(weekdaynum == 0){ //to change sunday to the last day of the week
weekdaynum = 6;
} else{
weekdaynum = weekdaynum-1;
}
var firstweek = curr.getDate() - weekdaynum;
var lastweek = firstweek + 6; // last day is the first day + 6
if((curr.getDate()-weekdaynum) <= 0){
var firstweek_lasmonth_lastdate = new Date(currweek.getFullYear(),currweek.getMonth(), 0);
var firstweek_diff = firstweek_lasmonth_lastdate.getDate()-Math.abs(firstweek);
var firstweekday = new Date(currweek.getFullYear(),currweek.getMonth()-1,firstweek_lasmonth_lastdate.getDate()+firstweek_diff);
var lastweekday = new Date(currweek.getFullYear(),currweek.getMonth()-1,firstweek_lasmonth_lastdate.getDate()+firstweek_diff+7);
} else{
var firstweekday = new Date(curr.setDate(firstweek));
var lastweekday = new Date(curr.setDate(lastweek));
}
So this will return (given date is: 2022/07/01):
firstweekday = Mon Jun 27 2022 00:00:00
lastweekday = Sun Jul 03 2022 00:00:00
Hope this helps.

krtek's method has some wrong,I tested this
var startDay = 0;
var weekStart = new Date(today.getDate() - (7 + today.getDay() - startDay) % 7);
var weekEnd = new Date(today.getDate() + (6 - today.getDay() - startDay) % 7);
it works

Although the question is seeming as obsolete I have to point out a problem.
Question: What will happen at 1st January 2016?
I think most of the above solutions calculate start of week as 27.12.2016.
For this reason I think, the correct calculation should be like the below simply;
var d = new Date(),
dayInMs = 1000 * 60 * 60 * 24,
weekInMs = dayInMs * 7,
startOfToday = new Date(d.getFullYear(), d.getMonth(), d.getDate()).valueOf(),
todayElapsedTime = d.valueOf() - startOfToday,
dayDiff = d.getDay() * dayInMs,
dateDiff = dayDiff + todayElapsedTime,
// finally
startOfWeek = d.valueOf() - dateDiff,
endOfWeek = startOfWeek + weekInMs - 1;

JavaScript
function getWeekDays(curr, firstDay = 1 /* 0=Sun, 1=Mon, ... */) {
var cd = curr.getDate() - curr.getDay();
var from = new Date(curr.setDate(cd + firstDay));
var to = new Date(curr.setDate(cd + 6 + firstDay));
return {
from,
to,
};
};
TypeScript
export enum WEEK_DAYS {
Sunday = 0,
Monday = 1,
Tuesday = 2,
Wednesday = 3,
Thursday = 4,
Friday = 5,
Saturday = 6,
}
export const getWeekDays = (
curr: Date,
firstDay: WEEK_DAYS = WEEK_DAYS.Monday
): { from: Date; to: Date } => {
const cd = curr.getDate() - curr.getDay();
const from = new Date(curr.setDate(cd + firstDay));
const to = new Date(curr.setDate(cd + 6 + firstDay));
return {
from,
to,
};
};

function getMonday(d) {
d = new Date(d);
var day = d.getDay(),
diff = d.getDate() - day + (day == 0 ? -6:1); // adjust when day is sunday
return new Date(d.setDate(diff));
}
console.log( getMonday(new Date(new Date().getFullYear(), new Date().getMonth(), new Date().getDate())) ) // Mon Nov 08 2010

Pure vanilla JS. no third party libraries.
const now = new Date()
const startOfWeek = new Date(now.getFullYear(), now.getMonth(), now.getDate() - now.getDay())
const endOfWeek = new Date(now.getFullYear(), now.getMonth(), startOfWeek.getDate() + 7)
^ this returns Sunday 00am to Sunday 00am. Adjust the "7" to get what you want.

var currentDate = new Date();
var firstday = new Date(currentDate.setDate(currentDate.getDate() - currentDate.getDay())).toUTCString();
var lastday = new Date(currentDate.setDate(currentDate.getDate() - currentDate.getDay() + 6)).toUTCString();
console.log("firstday", firstday);
console.log("lastday", lastday);

Works with different months and years.
let wDate = new Date();
let dDay = wDate.getDay() > 0 ? wDate.getDay() : 7;
let first = wDate.getDate() - dDay + 1;
let firstDayWeek = new Date(wDate.setDate(first));
let lastDayWeek = new Date(wDate.setDate(firstDayWeek.getDate()+6));
console.log(firstDayWeek.toLocaleDateString());
console.log(lastDayWeek.toLocaleDateString());

Nice suggestion but you got a small problem in lastday.
You should change it to:
lastday = new Date(firstday.getTime() + 60 * 60 *24 * 6 * 1000);

The moment approach worked for me for all the cases ( although i have not test the boundaries like year end , leap years ). Only Correction in the above code is the parameter is "isoWeek" , if you want to start the week from Monday.
let startOfWeek = moment().startOf("isoWeek").toDate();
let endOfWeek = moment().endOf("isoWeek").toDate();

We have added jquery code that shows the current week of days from monday to sunday.
var d = new Date();
var week = [];
var _days = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
var _months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
for (let i = 1; i <= 7; i++) {
let first = d.getDate() - d.getDay() + i;
let dt = new Date(d.setDate(first));
var _day = _days[dt.getDay()];
var _month = _months[dt.getMonth()];
var _date = dt.getDate();
if(_date < 10 ){
_date = '0' +_date;
}
var _year = dt.getFullYear();
var fulldate = _day+' '+_month+' '+_date+' '+_year+' ';
week.push(fulldate);
}
console.log(week);

An old question with lots of answers, so another one won't be an issue. Some general functions to get the start and end of all sorts of time units.
For startOf and endOf week, the start day of the week defaults to Sunday (0) but any day can be passed (Monday - 1, Tuesday - 2, etc.). Only uses Gregorian calendar though.
The functions don't mutate the source date, so to see if a date is in the same week as some other date (week starting on Monday):
if (d >= startOf('week', d1, 1) && d <= endOf('week', d1, 1)) {
// d is in same week as d1
}
or in the current week starting on Sunday:
if (d >= startOf('week') && d <= endOf('week')) {
// d is in the current week
}
// Returns a new Date object set to start of given unit
// For start of week, accepts any day as start
function startOf(unit, date = new Date(), weekStartDay = 0) {
// Copy original so don't modify it
let d = new Date(date);
let e = new Date(d);
e.setHours(23,59,59,999);
// Define methods
let start = {
second: d => d.setMilliseconds(0),
minute: d => d.setSeconds(0,0),
hour : d => d.setMinutes(0,0,0),
day : d => d.setHours(0,0,0,0),
week : d => {
start.day(d);
d.setDate(d.getDate() - d.getDay() + weekStartDay);
if (d > e) d.setDate(d.getDate() - 7);
},
month : d => {
start.day(d);
d.setDate(1);
},
year : d => {
start.day(d);
d.setMonth(0, 1);
},
decade: d => {
start.year(d);
let year = d.getFullYear();
d.setFullYear(year - year % 10);
},
century: d => {
start.year(d);
let year = d.getFullYear();
d.setFullYear(year - year % 100);
},
millenium: d => {
start.year(d);
let year = d.getFullYear();
d.setFullYear(year - year % 1000);
}
}
start[unit](d);
return d;
}
// Returns a new Date object set to end of given unit
// For end of week, accepts any day as start day
// Requires startOf
function endOf(unit, date = new Date(), weekStartDay = 0) {
// Copy original so don't modify it
let d = new Date(date);
let e = new Date(date);
e.setHours(23,59,59,999);
// Define methods
let end = {
second: d => d.setMilliseconds(999),
minute: d => d.setSeconds(59,999),
hour : d => d.setMinutes(59,59,999),
day : d => d.setHours(23,59,59,999),
week : w => {
w = startOf('week', w, weekStartDay);
w.setDate(w.getDate() + 6);
end.day(w);
d = w;
},
month : d => {
d.setMonth(d.getMonth() + 1, 0);
end.day(d);
},
year : d => {
d.setMonth(11, 31);
end.day(d);
},
decade: d => {
end.year(d);
let y = d.getFullYear();
d.setFullYear(y - y % 10 + 9);
},
century: d => {
end.year(d);
let y = d.getFullYear();
d.setFullYear(y - y % 100 + 99);
},
millenium: d => {
end.year(d);
let y = d.getFullYear();
d.setFullYear(y - y % 1000 + 999);
}
}
end[unit](d);
return d;
}
// Examples
let d = new Date();
['second','minute','hour','day','week','month','year',
'decade','century','millenium'].forEach(unit => {
console.log(('Start of ' + unit).padEnd(18) + ': ' +
startOf(unit, d).toString());
console.log(('End of ' + unit).padEnd(18) + ': ' +
endOf(unit, d).toString());
});

var currentDate = new Date();
var firstday = new Date(currentDate.setDate(currentDate.getDate() - currentDate.getDay())).toUTCString();
var lastday = new Date(currentDate.setDate(currentDate.getDate() - currentDate.getDay() + 7)).toUTCString();
console.log(firstday, lastday)
I'm using the following code in but because of .toUTCString() i'm receiving the following error as show in image.
if i remove .toUTCString(). output which i receive is not as expected

Small change to #SHIVA's answer which is a changed #Chris Lang answer.
For monday first usage with fix when today is sunday.
Date.prototype.GetFirstDayOfWeek = function() {
return (new Date(this.setDate(this.getDate() - this.getDay()+ (this.getDay() == 0 ? -6:1) )));
}
Date.prototype.GetLastDayOfWeek = function() {
return new Date(this.setDate(this.getDate() - (this.getDay() == 0 ? 7 : this.getDay()) + 7));
}
var today = new Date();
alert(today.GetFirstDayOfWeek());
alert(today.GetLastDayOfWeek());

You can try the below one too
let weekBgnDt = new Date();
let weekEndDt = new Date();
let wBeginDateLng, wEndDateLng, diffDays,dateCols=[];
if (weekBgnDt.getDay() > 0) {
diffDays = 0 - weekBgnDt.getDay();
weekBgnDt.setDate(weekBgnDt.getDate() + diffDays)
}
weekEndDt = weekEndDt.setDate(weekBgnDt.getDate() + 6)
wBeginDate = new Intl.DateTimeFormat('en-GB', { day: 'numeric', year: 'numeric',
month: '2-digit' }).format(weekBgnDt);
wEndDate = new Intl.DateTimeFormat('en-GB', { day: 'numeric', year: 'numeric', month:
'2-digit' }).format(weekEndDt);
wBeginDateLng = new Intl.DateTimeFormat('en-GB', { day: 'numeric', year: 'numeric',
month: 'long' }).format(weekBgnDt);
wEndDateLng = new Intl.DateTimeFormat('en-GB', { day: 'numeric', year: 'numeric',
month: 'long' }).format(weekEndDt);
console.log(wBeginDate, "-", wBeginDateLng)
console.log(wEndDate, "-", wEndDateLng)
for(let i=weekBgnDt;i<=weekEndDt;){
dateCols.push(new Intl.DateTimeFormat('en-GB', { day: 'numeric', year: 'numeric',
month: '2-digit' }).format(i));
i=weekBgnDt.setDate(weekBgnDt.getDate()+1)
}
console.log({wBeginDate,wBeginDateLng,wEndDate,wEndDateLng,dateCols})
The result will be printed as
{ wBeginDate: "16/05/2021", wBeginDateLng: "16 May 2021", wEndDate: "22/05/2021", wEndDateLng: "22 May 2021", dateCols: Array ["16/05/2021", "17/05/2021", "18/05/2021", "19/05/2021", "20/05/2021", "21/05/2021", "22/05/2021"] }

The right way to get the first and last date of the current week with appropriate month & year is as below
const curr = new Date();
const first = curr.getDate() - curr.getDay() + 1; // Start from Monday
const firstDate = new Date(curr.setDate(first));
const lastDate = new Date(curr.setDate(firstDate.getDate() + 6));
console.log(firstDate.toLocaleDateString(), lastDate.toLocaleDateString());

You can use this function, it works with first and last day of the week in different months or years
const getFirstAndLastDayOfTheWeek = () => {
// The starting time is the same current
let a = new Date();
let b = new Date();
const weekDay = a.getDay();
if (weekDay === 0) {
a.setDate(a.getDate() - 6);
} else if (weekDay === 1) {
b.setDate(b.getDate() + 7 - b.getDay());
} else if (weekDay >= 1) {
a.setDate(a.getDate() - a.getDay() + 1);
b.setDate(b.getDate() + 7 - b.getDay());
}
return { firstWeekDate: a, lastWeekDate: b };
}
console.log(getFirstAndLastDayOfTheWeek());

Is there a way that I can get the (first Sunday in October – first Sunday in April) with moment.js?

I know that I can use this for the start of the month moment().startOf('month') but I need the first Sunday of the month.

You could do this:
function getFirstWeekDay(dateString, dayOfWeek) {
var date = moment(dateString, "YYYY-MM-DD");
var day = date.day();
var diffDays = 0;
if (day > dayOfWeek) {
diffDays = 7 - (day - dayOfWeek);
} else {
diffDays = dayOfWeek - day
}
console.log(date.add(diffDays, 'day').format("YYYY-MM-DD"));
}
//Pass in the first of a given calendar month and the day weekday
getFirstWeekDay("2016-10-01", 0);
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.15.1/moment.min.js"></script>

Please check this Code.
var d = new Date();
var first_week = d.getDate();
var the_day = d.getDay();
if(first_week <= 7 && the_day == 0)
{
// It's the first Sunday of the month
// Do more stuff here
}

Here is the sample using js to get the first sunday of any month or year
function firstSunday(month, year) {
let tempDate = new Date();
tempDate.setHours(0,0,0,0);
// first SUNDAY of april
tempDate.setMonth(month);
tempDate.setYear(year);
tempDate.setDate(1);
let day = tempDate.getDay();
let toNextSun = day !== 0 ? 7 - day : 0;
tempDate.setDate(tempDate.getDate() + toNextSun);
return tempDate.toDateString();
}
console.log("april first sunday" , firstSunday(3 , 2020));
console.log("oct first sunday" , firstSunday(9 , 2020))