We Keep Coding

how to get first date and last date from month and year in javascript

Can any one help me to find first date and last date from month and year.
I have 2 parameter month and year, for example month = 10 and year = 2021
I tried some code but it doesn't have the answer
var prevMonthLastDay = new Date(2021, 10, 0);
var thisMonthFirstDay = new Date(2021, 10, 1);
console.log(prevMonthLastDay);
console.log(thisMonthFirstDay);
Above code is giving following output:
2021-10-30T17:00:00.000Z
2021-10-31T17:00:00.000Z
My expected answer is first date 2021-10-01 and last date 2021-10-31

Try the following to get your expected output:
function GetFirstAndLastDate(year, month)
{
var firstDayOfMonth = new Date(year, month-1, 2);
var lastDayOfMonth = new Date(year, month, 1);
console.log('First Day: ' + firstDayOfMonth.toISOString().substring(0, 10));
console.log('Last Day: ' + lastDayOfMonth.toISOString().substring(0, 10));
}
GetFirstAndLastDate(2021, 10);

You can try this way
var date = new Date();
var firstDay = new Date(date.getFullYear(), date.getMonth(), 1);
var lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);

I'm a little bit confused with what you really want to get referencing your variable names, so I include them all:
const currentYear = 2021;
const currentMonth = 10;
const prevMonthFirstDay = new Date(currentYear, currentMonth - 2, 1);
const prevMonthLastDay = new Date(currentYear, currentMonth - 1, 0);
const currentMonthFirstDay = new Date(currentYear, currentMonth - 1, 1);
const currentMonthLastDay = new Date(currentYear, currentMonth, 0);
const nextMonthFirstDay = new Date(currentYear, currentMonth, 1);
const nextMonthLastDay = new Date(currentYear, currentMonth + 1, 0);
console.log('prev month first day:', prevMonthFirstDay);
console.log('prev month last day:', prevMonthLastDay);
console.log('current month first day:', currentMonthFirstDay);
console.log('current month last day:', currentMonthLastDay);
console.log('next month first day:', nextMonthFirstDay);
console.log('next month last day:', nextMonthLastDay);
on my system this will gives:
prev month first day: Wed Sep 01 2021 00:00:00 GMT+0700 (Western Indonesia Time)
prev month last day: Thu Sep 30 2021 00:00:00 GMT+0700 (Western Indonesia Time)
current month first day: Fri Oct 01 2021 00:00:00 GMT+0700 (Western Indonesia Time)
current month last day: Sun Oct 31 2021 00:00:00 GMT+0700 (Western Indonesia Time)
next month first day: Mon Nov 01 2021 00:00:00 GMT+0700 (Western Indonesia Time)
next month last day: Tue Nov 30 2021 00:00:00 GMT+0700 (Western Indonesia Time)
so now it will only a matter of formatting:
console.log(currentMonthFirstDay.toLocaleDateString('en-GB').split('/').reverse().join('-'));
which will give you:
2021-10-01

You can follow this.
//first and last of the current month
var current_month = "April 2017";
var arrMonth = current_month.split(" ");
var first_day = new Date(arrMonth[0] + " 1 " + arrMonth[1]);
//even though I already have the values, I'm using date functions to get year and month
//because month is zero-based
var last_day = new Date(first_day.getFullYear(), first_day.getMonth() + 1, 0, 23, 59, 59);
//use moment,js to format
var start = moment(first_day).format("YYYY-MM-DD");
var end = moment(last_day).format("YYYY-MM-DD");
the answer is in the following link:
How to get last day of the month

You can try this way referrence
var date = new Date(), y = date.getFullYear(), m = date.getMonth();
var firstDay = new Date(y, m, 1);
var lastDay = new Date(y, m + 1, 0);

adding days to historical dates in app script [duplicate]

This question already has answers here:
How to add days to Date?
(56 answers)
Closed 2 years ago.
I am trying to pull some historical data, which has a variety of time stamps. I want the use to a user selected date, and then pull all days + some additional days.
Date1 is
var Date1 = "Thu Oct 22 00:00:00 GMT-04:00 2020"
var startDate = new Date(Date1)
var Enddate = new Date();
Enddate.setDate(startDate + 10);
This doesn't work. I cant seem to figure out how to add the "10 days" to the Date1 variable.

You need the getDate function of the Date object, and you'll need to pass the correct value when instantiating the new Date.
Try this:
var Date1 = "Thu Oct 22 00:00:00 GMT-04:00 2020"
var startDate = new Date(Date1);
// add it to startDate, using getDate()
startDate.setDate(startDate.getDate() + 10);
// now startDate will be 10 days later:
startDate; // Sun Nov 01 00:00:00 GMT-04:00 2020
// if you want an entirely new Date object, then instantiate a new one:
var Enddate = new Date(startDate);
If you want two different variables, then you can use the approach similar to what you tried, like so:
var Date1 = "Thu Oct 22 00:00:00 GMT-04:00 2020"
var startDate = new Date(Date1), second = new Date(Date1); // we're using another temporary variable
// add the days
second.setDate(second.getDate() + 10);
// now use Enddate with this
var Enddate = new Date(second);
Enddate; // Sun Nov 01 00:00:00 GMT-04:00 2020

You can't just add a number to a Date object to get a new date.
You can add to a date by:
getting the current day of the month with getDate()
adding a number of days to that result
setting the new date with setDate()
const Date1 = "Thu Oct 22 00:00:00 GMT-04:00 2020";
const addDays = 10;
const startDate = new Date(Date1);
const startDays = startDate.getDate();
const newDate = new Date(startDate);
newDate.setDate(startDays + addDays);
console.log('startDate:', startDate.toISOString());
console.log('newDate:', newDate.toISOString());
Note:
Passing a string into the Date constructor is discouraged, as it produces inconsistent results across browsers.
It is better to pass in the individual date and time values:
const Date1 = new Date(2020, 9, 22, 0, 0, 0);

Javascript setting date not working ok Chrome

Here's an issue I'm getting setting a date with Javascript on Chrome
"17-09-2019"
var [day, month, year] = date.split('-');
undefined
day
"17"
month
"09"
year
"2019"
var set_date = new Date(parseInt(year), parseInt(month), parseInt(day));
undefined
console.log(set_date);
VM5577:1 Thu Oct 17 2019 00:00:00 GMT+0300 (East Africa Time)
undefined
So I have a date 17-09-2019 and point here is 09 is September but when I set the date I get back October.
Been scratching my head over this one for a while now. Not sure what's going on.

The months in javascript starts from 0. You just need to subtract 1 to your parseInt(month):
var date = "17-09-2019";
var [day, month, year] = date.split('-');
console.log(`${day}-${month}-${year}`)
var set_date = new Date(parseInt(year), parseInt(month) - 1, parseInt(day));
console.log(set_date);

Set out this , month starting from index 0
var date = "17-09-2019"
var [day, month, year] = date.split('-');
month = month - 1;
var set_date = new Date(parseInt(year), parseInt(month), parseInt(day));
console.log(set_date); //Tue Sep 17 2019 00:00:00 GMT+0530 (India Standard Time)

new Date can't give me right time

startDate = "2019-03-07 (목) 12:00";
var year = startDate.slice(0,4);
var month = startDate.slice(5,7);
var day = startDate.slice(8,10);
var hour = startDate.slice(15,17);
var minute = startDate.slice(18,20);
var selEndDatetime = new Date(year, month, day, hour, minute);
console.log(selEndDatetime);
I want to see "Tue Mar 07 2019 12:00:00 GMT+0900 (한국 표준시)", but console shows me the message "Sun Apr 07 2019 12:00:00 GMT+0900 (한국 표준시)".
What is wrong this code and how can I modify it to get the desired output?

The month starts at 0. You need to parse month from string to integer and minus 1 when creating a date instance.
startDate = "2019-03-07 (목) 12:00";
var year = startDate.slice(0,4);
var month = parseInt(startDate.slice(5,7))
var day = startDate.slice(8,10);
var hour = startDate.slice(15,17);
var minute = startDate.slice(18,20);
var selEndDatetime = new Date(year, month - 1, day, hour, minute);
console.log(selEndDatetime);

You can simply pass the startDate string as an argument to the Date in order to create selEndDatetime
Code:
const startDate = '2019-03-07 (목) 12:00';
const selEndDatetime = new Date(startDate);
console.log(selEndDatetime);

How to get last day of the month

How can I obtain the last day of the month with the timestamp being 11:59:59 PM?

function LastDayOfMonth(Year, Month) {
return new Date((new Date(Year, Month, 1)) - 1);
}
console.log(LastDayOfMonth(2009, 11))
Example:
> LastDayOfMonth(2009, 11)
Mon Nov 30 2009 23:59:59 GMT+0100 (CET)

This will give you last day of current month.
var t= new Date();
alert(new Date(t.getFullYear(), t.getMonth() + 1, 0, 23, 59, 59));

var d = new Date();
console.log(d);
d.setMonth(d.getMonth() + 1); // set month as next month
console.log(d);
d.setDate(0); // get the last day of previous month
console.log(d);
Here is output from the code above:
Thu Oct 03 2013 11:34:59 GMT+0100 (GMT Daylight Time)
Sun Nov 03 2013 11:34:59 GMT+0000 (GMT Standard Time)
Thu Oct 31 2013 11:34:59 GMT+0000 (GMT Standard Time)

var d = new Date();
m = d.getMonth(); //current month
y = d.getFullYear(); //current year
alert(new Date(y,m,1)); //this is first day of current month
alert(new Date(y,m+1,0)); //this is last day of current month

var month = 1; // 1 for January
var d = new Date(2015, month, 0);
console.log(d); // last day in January

Sometimes all you have is a text version of the current month, ie: April 2017.
//first and last of the current month
var current_month = "April 2017";
var arrMonth = current_month.split(" ");
var first_day = new Date(arrMonth[0] + " 1 " + arrMonth[1]);
//even though I already have the values, I'm using date functions to get year and month
//because month is zero-based
var last_day = new Date(first_day.getFullYear(), first_day.getMonth() + 1, 0, 23, 59, 59);
//use moment,js to format
var start = moment(first_day).format("YYYY-MM-DD");
var end = moment(last_day).format("YYYY-MM-DD");

Last day of the month
now = new Date
lastDayOfTheMonth = new Date(1900+now.getYear(), now.getMonth()+1, 0)

Most of these answers are missing one thing or another. After playing with most of them I came up with the following that gives you the last possible millisecond of the month.
let testDate = new Date();
console.log(getMonthEnd(testDate));
function getMonthEnd(value) {
return new Date(value.getFullYear(), value.getMonth() + 1, 0, 23, 59, 59, 999);
}
Probably missing something in this one too but seems to cover all my requirements.

Calendar cal = Calendar.getInstance();
cal.set(Calendar.DATE, cal.getActualMaximum(Calendar.DATE));
Date lastDayOfMonth = cal.getTime();

Do not forget month started with 0 so +1 in month too.
let enddayofmonth = new Date(year, month, 0).getDate();