How to calculate days between two date excluding weekends in angularjs? [duplicate] - javascript

This question already has answers here:
Find day difference between two dates (excluding weekend days)
(13 answers)
Closed 3 years ago.
In my application i have two date picker as start date and end date. when user choose start and end date the system will show the days between two dates but excluding the saturday and sunday. How to calculate it by using angularjs?

Does something like this work:
var startDate = new Date("01-10-2020");
var endDate = new Date("01-20-2020");
var nextDay = new Date(startDate);
var cnt = 0;
do {
/*if (nextDay.getDay() >= 1 && nextDay.getDay() <= 5) {
cnt = cnt + 1;
}*/
cnt += (nextDay.getDay() >= 1 && nextDay.getDay() <= 5) ? 1 : 0;
nextDay.setDate(nextDay.getDate() + 1);
} while (nextDay <= endDate);
console.log("Number of week days between " + startDate + " and " + endDate + " = " + cnt);
Here is the fiddler.

You don't want to do an expensive loop over every day to see whether it is Saturday or Sunday. The logic should be as follows:
Work in UTC so we don't need to worry about time zone
Calculate total number of calendar weeks. In a single calendar week, there are guaranteed to be 5 weekdays (not weekends == SAT || SUN)
Calculate the remainder of days. This will be added to the calculation later.
Determine the "finalAdjustment" by seeing if the remainder falls on weekend days.
The number of weekdays is (5 * numWeeks) + remainderDays + finalAdjust
(function() {
"use strict";
var SUN = 0;
var MON = 1;
var TUE = 2;
var WED = 3;
var THU = 4;
var FRI = 5;
var SAT = 6;
function isWeekendDay(day) {
return day === SAT || day === SUN;
}
function numberWeekDays(start, end) {
var numCalendarDays = (end - start) / 1000 / 60 / 60 / 24;
var numWeeks = Math.floor(numCalendarDays / 7);
// Potential days to add on to the number of full calendar
// weeks. This will be adjusted by "finalAdjust"
var remainderDays = numCalendarDays % 7;
// Adjustments for start and end dates being on a weekend
// ----------------------------
// Start at one because the same day should count as 1
// but number of days between same day is 0 based on
// arithmetic above.
// Change this to 0 if you don't want end date inclusive...
var finalAdjust = 1;
var startDay = start.getUTCDay();
var endDay = end.getUTCDay();
// On a weekend, so adjust by subtracting 1
if (isWeekendDay(startDay)) {
finalAdjust--;
}
// On a weekend, so adjust by subtracting 1
if (isWeekendDay(endDay)) {
finalAdjust--;
}
// This accounts for subtracting an extra weekend when starting
// at the beginning of a weekend (e.g. Saturday into Monday)
// The end day cannot also be on a weekend based on week modular division (mod 7)
if (startDay === SAT && remainderDays > 2) {
finalAdjust--;
}
// ---------------------------
// For every full calendar week there are 5 week days
// Use that number with the remainderDays and finalAdjust above
// to arrive at the answer.
var numWeekDays = (5 * numWeeks) + remainderDays + finalAdjust;
return numWeekDays;
}
// Test cases
// Assume that the start and end dates are inclusive
// 2020-01-01 to 2020-01-01 is one day
// 2020-01-01 to 2020-01-02 is two days
// ----------------------
// A Wednesdday
var start = new Date("2020-01-08");
// A Saturday
var end = new Date("2020-02-01");
// Expected answer: 18
console.log(numberWeekDays(start, end));
// A Saturday
start = new Date("2020-01-05");
// A Monday
end = new Date("2020-01-31");
// Expected answer: 20
console.log(numberWeekDays(start, end));
// Weekday to weekday Tuesday to
start = new Date("2020-01-07");
end = new Date("2020-01-16");
// Expected: 8
console.log(numberWeekDays(start, end));
// Same week: Mon-Wed
start = new Date("2020-01-06");
end = new Date("2020-01-08");
// Expected answer: 3
console.log(numberWeekDays(start, end));
// Same day
start = new Date("2020-01-08");
end = new Date("2020-01-08");
// Expect: 1
console.log(numberWeekDays(start, end));
// Weekend only
start = new Date("2020-01-04");
end = new Date("2020-01-05");
// Expect: 0;
console.log(numberWeekDays(start, end));
// ------------------
}());
As others have stated, a date library like moment is useful here because it gives you a lot of utility functions for working with dates and durations.

Related

how to write day from numbers in javascript?

How would I write this expression in JavaScript?
It is to represent a date that is 2 weeks, counted by each passing Thursday, but excludes the thursday of the week the date was made.
NeededDay = Today + (18 - DayOfWeek(today))
or since it is Wednesday, it could be written?
var date = new Date();
var NeededDate = date.getDay() + (18-3);
or
I wrote this but I do not know if it is right?
var value = 3;
var GivenDate = value;
var GivenDay = value.getDay();
var daysToSecondThursday = Givenday2.setDate(GivenDay + Givenday2.setDate(18 - GivenDay));
alert("two weeks after next thursday is = " + daysToSecondThursday.val());
what is the correct way? ?
You could use:
function GetThursdayIn2Weeks(date)
{
var day = date.getDay();
// Add 2 weeks.
var newDate = new Date(date.setTime(date.getTime() + (14 * 86400000)));
// Adjust for Thursday.
var adjust = 4 - day;
if (adjust <= 0) // Might need to be changed - See comments!
adjust +=7;
// Apply Thursday adjustment.
newDate = new Date(newDate.setTime(newDate.getTime() + (adjust * 86400000)));
return newDate;
}
If the date passed in is Thursday, then it will return two weeks from the following Thursday. If this is not what you want, then adjust the if (adjust <= 0) code above to be:
if (adjust < 0)
Here is a jsFiddle: http://jsfiddle.net/kgjertsen/ec7vnezn/

exclude weekends in javascript date calculation

I have two sets of codes that work. Needed help combining them into one.
This code gets me the difference between two dates. works perfectly:
function test(){
var date1 = new Date(txtbox_1.value);
var date2 = new Date(txtbox_2.value);
var diff = (date2 - date1)/1000;
var diff = Math.abs(Math.floor(diff));
var days = Math.floor(diff/(24*60*60));
var leftSec = diff - days * 24*60*60;
var hrs = Math.floor(leftSec/(60*60));
var leftSec = leftSec - hrs * 60*60;
var min = Math.floor(leftSec/(60));
var leftSec = leftSec - min * 60;
txtbox_3.value = days + "." + hrs; }
source for the above code
The code below by #cyberfly appears to have the answer of excluding sat and sun which is what i needed. source. However, its in jquery and the above code is in JS. Therefore, needed help combining as i lacked that knowledge :(
<script type="text/javascript">
$("#startdate, #enddate").change(function() {
var d1 = $("#startdate").val();
var d2 = $("#enddate").val();
var minutes = 1000*60;
var hours = minutes*60;
var day = hours*24;
var startdate1 = getDateFromFormat(d1, "d-m-y");
var enddate1 = getDateFromFormat(d2, "d-m-y");
var days = calcBusinessDays(new Date(startdate1),new Date(enddate1));
if(days>0)
{ $("#noofdays").val(days);}
else
{ $("#noofdays").val(0);}
});
</script>
EDIT
Made an attempt at combining the codes. here is my sample. getting object expected error.
function test(){
var date1 = new Date(startdate.value);
var date2 = new Date(enddate.value);
var diff = (date2 - date1)/1000;
var diff = Math.abs(Math.floor(diff));
var days = Math.floor(diff/(24*60*60));
var leftSec = diff - days * 24*60*60;
var hrs = Math.floor(leftSec/(60*60));
var leftSec = leftSec - hrs * 60*60;
var min = Math.floor(leftSec/(60));
var leftSec = leftSec - min * 60;
var startdate1 = getDateFromFormat(startdate, "dd/mm/yyyy hh:mm");
var enddate1 = getDateFromFormat(enddate, "dd/mm/yyyy hh:mm");
days = calcBusinessDays(new Date(startdate1),new Date(enddate1));
noofdays.value = days + "." + hrs; }
start: <input type="text" id="startdate" name="startdate" value="02/03/2015 00:00">
end: <input type="text" id="enddate" name="enddate" value="02/03/2015 00:01">
<input type="text" id="noofdays" name="noofdays" value="">
When determining the number of days between two dates, there are lots of decisions to be made about what is a day. For example, the period 1 Feb to 2 Feb is generally one day, so 1 Feb to 1 Feb is zero days.
When adding the complexity of counting only business days, things get a lot tougher. E.g. Monday 2 Feb 2015 to Friday 6 February is 4 elapsed days (Monday to Tuesday is 1, Monday to Wednesday is 2, etc.), however the expression "Monday to Friday" is generally viewed as 5 business days and the duration Mon 2 Feb to Sat 7 Feb should also be 4 business days, but Sunday to Saturday should be 5.
So here's my algorithm:
Get the total number of whole days between the two dates
Divide by 7 to get the number of whole weeks
Multiply the number of weeks by two to get the number of weekend days
Subtract the number of weekend days from the whole to get business days
If the number of total days is not an even number of weeks, add the numbe of weeks * 7 to the start date to get a temp date
While the temp date is less than the end date:
if the temp date is not a Saturday or Sunday, add one the business days
add one to the temp date
That's it.
The stepping part at the end can probably be replaced by some other algorithm, but it will never loop for more than 6 days so it's a simple and reasonably efficient solution to the issue of uneven weeks.
Some consequences of the above:
Monday to Friday is 4 business days
Any day to the same day in a different week is an even number of weeks and therefore an even mutiple of 5, e.g. Monday 2 Feb to Monday 9 Feb and Sunday 1 Feb to Sunday 8 Feb are 5 business days
Friday 6 Feb to Sunday 7 Feb is zero business days
Friday 6 Feb to Monday 9 Feb is one business day
Sunday 8 Feb to: Sunday 15 Feb, Sat 14 Feb and Fri 13 Feb are all 5 business days
Here's the code:
// Expects start date to be before end date
// start and end are Date objects
function dateDifference(start, end) {
// Copy date objects so don't modify originals
var s = new Date(+start);
var e = new Date(+end);
// Set time to midday to avoid dalight saving and browser quirks
s.setHours(12,0,0,0);
e.setHours(12,0,0,0);
// Get the difference in whole days
var totalDays = Math.round((e - s) / 8.64e7);
// Get the difference in whole weeks
var wholeWeeks = totalDays / 7 | 0;
// Estimate business days as number of whole weeks * 5
var days = wholeWeeks * 5;
// If not even number of weeks, calc remaining weekend days
if (totalDays % 7) {
s.setDate(s.getDate() + wholeWeeks * 7);
while (s < e) {
s.setDate(s.getDate() + 1);
// If day isn't a Sunday or Saturday, add to business days
if (s.getDay() != 0 && s.getDay() != 6) {
++days;
}
}
}
return days;
}
I don't know how it compares to jfriend00's answer or the code you referenced, if you want the period to be inclusive, just add one if the start or end date are a business day.
Here's a simple function to calculate the number of business days between two date objects. As designed, it does not count the start day, but does count the end day so if you give it a date on a Tuesday of one week and a Tuesday of the next week, it will return 5 business days. This does not account for holidays, but does work properly across daylight savings changes.
function calcBusinessDays(start, end) {
// This makes no effort to account for holidays
// Counts end day, does not count start day
// make copies we can normalize without changing passed in objects
var start = new Date(start);
var end = new Date(end);
// initial total
var totalBusinessDays = 0;
// normalize both start and end to beginning of the day
start.setHours(0,0,0,0);
end.setHours(0,0,0,0);
var current = new Date(start);
current.setDate(current.getDate() + 1);
var day;
// loop through each day, checking
while (current <= end) {
day = current.getDay();
if (day >= 1 && day <= 5) {
++totalBusinessDays;
}
current.setDate(current.getDate() + 1);
}
return totalBusinessDays;
}
And, the jQuery + jQueryUI code for a demo:
// make both input fields into date pickers
$("#startDate, #endDate").datepicker();
// process click to calculate the difference between the two days
$("#calc").click(function(e) {
var diff = calcBusinessDays(
$("#startDate").datepicker("getDate"),
$("#endDate").datepicker("getDate")
);
$("#diff").html(diff);
});
And, here's a simple demo built with the date picker in jQueryUI: http://jsfiddle.net/jfriend00/z1txs10d/
const firstDate = new Date("December 30, 2020");
const secondDate = new Date("January 4, 2021");
const daysWithOutWeekEnd = [];
for (var currentDate = new Date(firstDate); currentDate <= secondDate; currentDate.setDate(currentDate.getDate() + 1)) {
// console.log(currentDate);
if (currentDate.getDay() != 0 && currentDate.getDay() != 6) {
daysWithOutWeekEnd.push(new Date(currentDate));
}
}
console.log(daysWithOutWeekEnd, daysWithOutWeekEnd.length);
#RobG has given an excellent algorithm to separate business days from weekends.
I think the only problem is if the starting days is a weekend, Saturday or Sunday, then the no of working days/weekends will one less.
Corrected code is below.
function dateDifference(start, end) {
// Copy date objects so don't modify originals
var s = new Date(start);
var e = new Date(end);
var addOneMoreDay = 0;
if( s.getDay() == 0 || s.getDay() == 6 ) {
addOneMoreDay = 1;
}
// Set time to midday to avoid dalight saving and browser quirks
s.setHours(12,0,0,0);
e.setHours(12,0,0,0);
// Get the difference in whole days
var totalDays = Math.round((e - s) / 8.64e7);
// Get the difference in whole weeks
var wholeWeeks = totalDays / 7 | 0;
// Estimate business days as number of whole weeks * 5
var days = wholeWeeks * 5;
// If not even number of weeks, calc remaining weekend days
if (totalDays % 7) {
s.setDate(s.getDate() + wholeWeeks * 7);
while (s < e) {
s.setDate(s.getDate() + 1);
// If day isn't a Sunday or Saturday, add to business days
if (s.getDay() != 0 && s.getDay() != 6) {
++days;
}
//s.setDate(s.getDate() + 1);
}
}
var weekEndDays = totalDays - days + addOneMoreDay;
return weekEndDays;
}
JSFiddle link is https://jsfiddle.net/ykxj4k09/2/
First Get the Number of Days in a month
totalDays(month, year) {
return new Date(year, month, 0).getDate();
}
Then Get No Of Working Days In A Month By removing Saturday and Sunday
totalWorkdays() {
var d = new Date(); // to know present date
var m = d.getMonth() + 1; // to know present month
var y = d.getFullYear(); // to knoow present year
var td = this.totalDays(m, y);// to get no of days in a month
for (var i = 1; i <= td; i++) {
var s = new Date(y, m - 1, i);
if (s.getDay() != 0 && s.getDay() != 6) {
this.workDays.push(s.getDate());// working days
}else {
this.totalWeekDays.push(s.getDate());//week days
}
}
this.totalWorkingDays = this.workDays.length;
}
I thought the above code snippets others shared are lengthy.
I am sharing a concise snippet that gives date after considering the total number of days specified. we can also customize dates other than Saturdays and Sundays.
function getBusinessDays(dateObj, days) {
for (var i = 0; i < days; i++) {
if (days > 0) {
switch (dateObj.getDay()) {
// 6 being Saturday and 0 being Sunday.
case 6, 0:
dateObj.setDate(dateObj.getDate() + 2)
break;
//5 = Friday.
case 5:
dateObj.setDate(dateObj.getDate() + 3)
break;
//handle Monday, Tuesday, Wednesday and Thursday!
default:
dateObj.setDate(dateObj.getDate() + 1)
//console.log(dateObj)
break;
}
}
}
return dateObj;
}
console.log(getBusinessDays(new Date(), 11))
//Mon Dec 20 2021 18:56:01 GMT+0530 (India Standard Time)

Calculate number of specific weekdays between dates

I'm trying to calculate the number of Mondays, Wednesdays, and Fridays between 2 dates in Tasker, thus I need a math formula, possibly utilizing the date in seconds form, i.e. unix time, or a javascript code. I've tried Googling and racking my brain for any way to even start this and I'm lost so I haven't tried anything yet. The only thing I could think of was getting the total number of days and dividing by 7, but that clearly does not help me very much, especially if one or both of the days is midweek. Can anyone point me in a better direction?
How to count specific days of the week between two dates in O(1):
// days is an array of weekdays: 0 is Sunday, ..., 6 is Saturday
function countCertainDays( days, d0, d1 ) {
var ndays = 1 + Math.round((d1-d0)/(24*3600*1000));
var sum = function(a,b) {
return a + Math.floor( ( ndays + (d0.getDay()+6-b) % 7 ) / 7 ); };
return days.reduce(sum,0);
}
Example on counting Mondays, Wednesdays, and Fridays [1,3,5] between two dates:
countCertainDays([1,3,5],new Date(2014,8,1),new Date(2014,8,1)) // 1
countCertainDays([1,3,5],new Date(2014,8,1),new Date(2014,8,2)) // 1
countCertainDays([1,3,5],new Date(2014,8,1),new Date(2014,8,3)) // 2
countCertainDays([1,3,5],new Date(2014,8,1),new Date(2014,8,4)) // 2
countCertainDays([1,3,5],new Date(2014,8,1),new Date(2014,8,5)) // 3
countCertainDays([1,3,5],new Date(2014,8,1),new Date(2014,8,6)) // 3
countCertainDays([1,3,5],new Date(2014,8,1),new Date(2014,8,7)) // 3
Note that the month parameter to Date is 0-based, so 1 Sept 2014 is Date(2014,8,1).
Assume total number of days is n. Then number of any day of a week is initially n / 7. Now take n = n % 7. Depending on the value of current n you can easily calculate the final count of days.
As example:
Assume your first day is Friday and total number of days is 100. So, n = 100. There are minimum 100/7 or 14 of each weekday is in the interval. 100 % 7 = 2. So final count is,
Friday -> 14+1 = 15
Saturday -> 14+1 = 15
Sunday -> 14
Monday -> 14
Tuesday -> 14
Wednesday -> 14
Thursday -> 14
const start_date = "2022-06-02";// standard date format YYYY-MM-DD
const end_date = "2022-06-18";
const days = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]; // standard week days
const getNumberOfWeekDays = (day) => {
// this will return number of week days between given start and end date
const startDay = moment(start_date).format("ddd");
const index = days.indexOf(startDay); // index of the start day
const totalDays = moment(end_date).diff(moment(start_date), "days"); // 16
const numberOfDays = Math.round(totalDays / 7); // 16/7 = 2; number of sessions by week
const remainingDays = totalDays % 7; // 16 % 7 = 2
const newArray = days.rotate(index).slice(0, remainingDays); // ["Thu","Fri"]
if (newArray.includes(day)) {
return numberOfDays + 1;
}
return numberOfDays;
};
getNumberOfWeekDays('Thu');// Thursday between given start and end date is 3
getNumberOfWeekDays('Mon');// Wednesday between given start and end date is 2
How to count the number of friday between two date in JavaScript
function myfunction() {
var frist = document.getElementById("dt_VacStart").value
var answer = 0;
var second = document.getElementById("dt_VacEnd").value;
if (frist != null && second != null) {
var startDate = new Date(frist);
var endDate = new Date(second);
var totalfriday = 0;
for (var i = startDate; i <= endDate;) {
if (i.getDay() ==5) {
totalfriday++;
}
i.setTime(i.getTime() + 1000 * 60 * 60 * 24);
}
document.getElementById('<%=Friday.ClientID%>').value = totalfriday;
} else {
totalfriday = 0;
document.getElementById('<%=Friday.ClientID%>').value = totalfriday;
}
}

Javascript - Age Verification

Hey javascript masters,
Attempting to create an age verification page to a client's site. Code below is not functioning as it doesn't matter what year you select, it will still allow you to enter the site. Not sure what I should be looking at to correct.
Any help is appreciated.
<script type="text/javascript"><!--
function checkAge(f){
var dob=new Date();
var date=dob.getDate();
var month=dob.getMonth() + 1;
var year=dob.getFullYear();
var cmbmonth=parseInt(document.getElementById("cmbmonth").options[document.getElementById("cmbmonth").selectedIndex].value);
var cmbday=parseInt(document.getElementById("cmbday").options[document.getElementById("cmbday").selectedIndex].value);
var cmbyear=parseInt(document.getElementById("cmbyear").options[document.getElementById("cmbyear").selectedIndex].value);
age=year-cmbyear;
if(cmbmonth>month){age--;}
else{if(cmbmonth==month && cmbday>=date){age--;}}
if(cmbmonth==0){alert("You must enter the month you were born in.");return false;}
else if(cmbday==0){alert("You must enter the day you were born on.");return false;}
else if(cmbyear==2005){alert("You must enter the year you were born in.");return false;}
else if(age<13){alert("You are unable to view this site!");location.replace("http://www.dharmatalks.org");return false;}
else{return true;}
}
// --></script>
Calculating age in years, months and days is a bit trickier than it should be due to the differences in month and year lengths. Here's a function that will return the difference between two dates in years, months, days, hours, minutes and seconds.
function dateDifference(start, end) {
// Copy date objects so don't modify originals
var s = new Date(+start);
var e = new Date(+end);
var timeDiff, years, months, days, hours, minutes, seconds;
// Get estimate of year difference
years = e.getFullYear() - s.getFullYear();
// Add difference to start, if greater than end, remove one year
// Note start from restored start date as adding and subtracting years
// may not be symetric
s.setFullYear(s.getFullYear() + years);
if (s > e) {
--years;
s = new Date(+start);
s.setFullYear(s.getFullYear() + years);
}
// Get estimate of months
months = e.getMonth() - s.getMonth();
months += months < 0? 12 : 0;
// Add difference to start, adjust if greater
s.setMonth(s.getMonth() + months);
if (s > e) {
--months;
s = new Date(+start);
s.setFullYear(s.getFullYear() + years);
s.setMonth(s.getMonth() + months);
}
// Get remaining time difference, round to next full second
timeDiff = (e - s + 999) / 1e3 | 0;
days = timeDiff / 8.64e4 | 0;
hours = (timeDiff % 8.64e4) / 3.6e3 | 0;
minutes = (timeDiff % 3.6e3) / 6e1 | 0;
seconds = timeDiff % 6e1;
return [years, months, days, hours, minutes, seconds];
}
You can abbreviate the above just after the year part and return just that if you want.
Note that in your code:
var cmbmonth=parseInt(document.getElementById("cmbmonth").options[document.getElementById("cmbmonth").selectedIndex].value);
can be:
var cmbmonth = document.getElementById("cmbmonth").value;
There is no need for parseInt, the Date constructor will happily work with string values. If you have used calendar month numbers for the values (i.e. Jan = 1) then subtract 1 before giving it to the Date constructor, but simpler to use javascript month indexes for the values (i.e. Jan = 0).
You can then do:
var diff = dateDifference(new Date(cmbyear, cmbmonth, cmbdate), new Date());
if (diff[0] < 18) {
// sorry, under 18
}

JavaScript Date.getWeek()? [duplicate]

This question already has answers here:
Get week of year in JavaScript like in PHP
(23 answers)
Closed 5 years ago.
I'm looking for a tested solid solution for getting current week of the year for specified date. All I can find are the ones that doesn't take in account leap years or just plain wrong. Does anyone have this type of stuff?
Or even better a function that says how many weeks does month occupy. It is usually 5, but can be 4 (feb) or 6 (1st is sunday and month has 30-31 days in it)
=================
UPDATE:
Still not sure about getting week #, but since I figured out it won't solve my problem with calculating how many weeks month occupy, I abandoned it.
Here's a function to find out how many weeks exactly month occupy on the calendar:
getWeeksNum: function(year, month) {
var daysNum = 32 - new Date(year, month, 32).getDate(),
fDayO = new Date(year, month, 1).getDay(),
fDay = fDayO ? (fDayO - 1) : 6,
weeksNum = Math.ceil((daysNum + fDay) / 7);
return weeksNum;
}
/**
* Returns the week number for this date. dowOffset is the day of week the week
* "starts" on for your locale - it can be from 0 to 6. If dowOffset is 1 (Monday),
* the week returned is the ISO 8601 week number.
* #param int dowOffset
* #return int
*/
Date.prototype.getWeek = function (dowOffset) {
/*getWeek() was developed by Nick Baicoianu at MeanFreePath: http://www.meanfreepath.com */
dowOffset = typeof(dowOffset) == 'number' ? dowOffset : 0; //default dowOffset to zero
var newYear = new Date(this.getFullYear(),0,1);
var day = newYear.getDay() - dowOffset; //the day of week the year begins on
day = (day >= 0 ? day : day + 7);
var daynum = Math.floor((this.getTime() - newYear.getTime() -
(this.getTimezoneOffset()-newYear.getTimezoneOffset())*60000)/86400000) + 1;
var weeknum;
//if the year starts before the middle of a week
if(day < 4) {
weeknum = Math.floor((daynum+day-1)/7) + 1;
if(weeknum > 52) {
nYear = new Date(this.getFullYear() + 1,0,1);
nday = nYear.getDay() - dowOffset;
nday = nday >= 0 ? nday : nday + 7;
/*if the next year starts before the middle of
the week, it is week #1 of that year*/
weeknum = nday < 4 ? 1 : 53;
}
}
else {
weeknum = Math.floor((daynum+day-1)/7);
}
return weeknum;
};
Usage:
var mydate = new Date(2011,2,3); // month number starts from 0
// or like this
var mydate = new Date('March 3, 2011');
alert(mydate.getWeek());
Source
For those looking for a more simple approach;
Date.prototype.getWeek = function() {
var onejan = new Date(this.getFullYear(),0,1);
var today = new Date(this.getFullYear(),this.getMonth(),this.getDate());
var dayOfYear = ((today - onejan + 86400000)/86400000);
return Math.ceil(dayOfYear/7)
};
Use with:
var today = new Date();
var currentWeekNumber = today.getWeek();
console.log(currentWeekNumber);
Consider using my implementation of "Date.prototype.getWeek", think is more accurate than the others i have seen here :)
Date.prototype.getWeek = function(){
// We have to compare against the first monday of the year not the 01/01
// 60*60*24*1000 = 86400000
// 'onejan_next_monday_time' reffers to the miliseconds of the next monday after 01/01
var day_miliseconds = 86400000,
onejan = new Date(this.getFullYear(),0,1,0,0,0),
onejan_day = (onejan.getDay()==0) ? 7 : onejan.getDay(),
days_for_next_monday = (8-onejan_day),
onejan_next_monday_time = onejan.getTime() + (days_for_next_monday * day_miliseconds),
// If one jan is not a monday, get the first monday of the year
first_monday_year_time = (onejan_day>1) ? onejan_next_monday_time : onejan.getTime(),
this_date = new Date(this.getFullYear(), this.getMonth(),this.getDate(),0,0,0),// This at 00:00:00
this_time = this_date.getTime(),
days_from_first_monday = Math.round(((this_time - first_monday_year_time) / day_miliseconds));
var first_monday_year = new Date(first_monday_year_time);
// We add 1 to "days_from_first_monday" because if "days_from_first_monday" is *7,
// then 7/7 = 1, and as we are 7 days from first monday,
// we should be in week number 2 instead of week number 1 (7/7=1)
// We consider week number as 52 when "days_from_first_monday" is lower than 0,
// that means the actual week started before the first monday so that means we are on the firsts
// days of the year (ex: we are on Friday 01/01, then "days_from_first_monday"=-3,
// so friday 01/01 is part of week number 52 from past year)
// "days_from_first_monday<=364" because (364+1)/7 == 52, if we are on day 365, then (365+1)/7 >= 52 (Math.ceil(366/7)=53) and thats wrong
return (days_from_first_monday>=0 && days_from_first_monday<364) ? Math.ceil((days_from_first_monday+1)/7) : 52;
}
You can check my public repo here https://bitbucket.org/agustinhaller/date.getweek (Tests included)
Get week number
Date.prototype.getWeek = function() {
var dt = new Date(this.getFullYear(),0,1);
return Math.ceil((((this - dt) / 86400000) + dt.getDay()+1)/7);
};
var myDate = new Date(2013, 3, 25); // 2013, 25 April
console.log(myDate.getWeek());
I know this is an old question, but maybe it helps:
http://weeknumber.net/how-to/javascript
// This script is released to the public domain and may be used, modified and
// distributed without restrictions. Attribution not necessary but appreciated.
// Source: https://weeknumber.net/how-to/javascript
// Returns the ISO week of the date.
Date.prototype.getWeek = function() {
var date = new Date(this.getTime());
date.setHours(0, 0, 0, 0);
// Thursday in current week decides the year.
date.setDate(date.getDate() + 3 - (date.getDay() + 6) % 7);
// January 4 is always in week 1.
var week1 = new Date(date.getFullYear(), 0, 4);
// Adjust to Thursday in week 1 and count number of weeks from date to week1.
return 1 + Math.round(((date.getTime() - week1.getTime()) / 86400000
- 3 + (week1.getDay() + 6) % 7) / 7);
}
// Returns the four-digit year corresponding to the ISO week of the date.
Date.prototype.getWeekYear = function() {
var date = new Date(this.getTime());
date.setDate(date.getDate() + 3 - (date.getDay() + 6) % 7);
return date.getFullYear();
}
/*get the week number by following the norms of ISO 8601*/
function getWeek(dt){
var calc=function(o){
if(o.dtmin.getDay()!=1){
if(o.dtmin.getDay()<=4 && o.dtmin.getDay()!=0)o.w+=1;
o.dtmin.setDate((o.dtmin.getDay()==0)? 2 : 1+(7-o.dtmin.getDay())+1);
}
o.w+=Math.ceil((((o.dtmax.getTime()-o.dtmin.getTime())/(24*60*60*1000))+1)/7);
},getNbDaysInAMonth=function(year,month){
var nbdays=31;
for(var i=0;i<=3;i++){
nbdays=nbdays-i;
if((dtInst=new Date(year,month-1,nbdays)) && dtInst.getDate()==nbdays && (dtInst.getMonth()+1)==month && dtInst.getFullYear()==year)
break;
}
return nbdays;
};
if(dt.getMonth()+1==1 && dt.getDate()>=1 && dt.getDate()<=3 && (dt.getDay()>=5 || dt.getDay()==0)){
var pyData={"dtmin":new Date(dt.getFullYear()-1,0,1,0,0,0,0),"dtmax":new Date(dt.getFullYear()-1,11,getNbDaysInAMonth(dt.getFullYear()-1,12),0,0,0,0),"w":0};
calc(pyData);
return pyData.w;
}else{
var ayData={"dtmin":new Date(dt.getFullYear(),0,1,0,0,0,0),"dtmax":new Date(dt.getFullYear(),dt.getMonth(),dt.getDate(),0,0,0,0),"w":0},
nd12m=getNbDaysInAMonth(dt.getFullYear(),12);
if(dt.getMonth()==12 && dt.getDay()!=0 && dt.getDay()<=3 && nd12m-dt.getDate()<=3-dt.getDay())ayData.w=1;else calc(ayData);
return ayData.w;
}
}
alert(getWeek(new Date(2017,01-1,01)));

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