Develop Reference

Javascript : Increase a Date object by a year

I'm assign a new date object to my object attribute like that :
giftObject.purshasedDate = new Date()
which give a date format :
Date Thu Feb 20 2020 13:36:37 GMT+0100 (heure normale d’Europe
centrale)
I want to increase this date by one year, I tried :
new Date().setFullYear(giftObject.purshasedDate.getFullYear() + 1) but it give a number serial like this : 1613824899244
I do not understand what that number serial mean! it's a date or should a try some thing else ?

By default all dates object are timestamps.
JavaScript Date objects represent a single moment in time in a
platform-independent format. Date objects contain a Number that
represents milliseconds since 1 January 1970 UTC.
Source : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
I think the default new Date() object can display itself to string by in fact it's also a timestamp.
If you want to display a date as string, you have to use the toLocaleString() method on Date.
I tried by updating the original date and it return the string of the date, don't know why but it's work by updating the original date.
Example :
let giftObject = {};
giftObject.purshasedDate = new Date();
giftObject.purshasedDate.setFullYear(giftObject.purshasedDate.getFullYear() + 1);
console.log(giftObject.purshasedDate)
Result : "20/02/2021 à 13:55:49" for my French browser

const oldDate = new Date("Date Thu Feb 20 2020 13:36:37 GMT+0100")
const newDate = oldDate.setFullYear(oldDate.getFullYear() + 1)
const dateWithPlusOneYear = new Date(newDate)
console.log(new Date(dateWithPlusOneYear))
//Sat Feb 20 2021 13:36:37 GMT+0100 (Central European Standard Time)

Please use this one:
purshasedDate = new Date();
purshasedDate = new Date(purshasedDate.setFullYear(purshasedDate.getFullYear() + 1));

Angular : Convert Object into Date and Moment

I am receiving a form value for date in Kendo Datepicker. It comes in as an object.
1)
How do I convert the following to date?
The following in Debugger still left it as Object
new Date(this.editHeaderAddressForm.value.seasonalEnd);
2) Additionally, how can I convert it to Moment?

The Date.parse() method parses a string representation of a date, and returns the number of milliseconds
var javaScriptRelease = Date.parse('04 Dec 1995 00:12:00 GMT');
var newDate = Date('December 17, 1995 03:24:00');
console.log(javaScriptRelease);
> // expected output: 818035920000
console.log(newDate);
> // expected output: Sun Dec 17 1995 03:24:00 GMT...

You can get date, and moment with short and simple code.
var full_time = new Date(this.editHeaderAddressForm.value.seasonalEnd);
var date = full_time.toLocaleDateString();
var moment = full_time.toLocaleTimeString();
console.log(date);
console.log(moment);

Use Date.parse method
const epochValue = Date.parse(this.editHeaderAddressForm.value.seasonalEnd);
This will return date in EPOCH this you can directly pass in to Moment function as well.
moment.unix(epochValue)

What does my date time get converted into from ASP.Net MVC to Javascript

In my html file I'm passing an array of objects with a date time to javascript like this
<script>
var TimerEvents = #Html.Raw(Json.Encode(Model.PendingTimerEvents));
</script>
my 'TimerEvents' has an EventTime property that when I read in Javascript looks like this
"/Date(1521617700000)/"
and I want to get this value, whatever it is, into a Javascript Date() object.
like this
var countDownDate = new Date(date here).getTime();
What is that format, and how would I do this?

the value you get is a milisecond representation of the date, I think the count starts at 1/1/1970.
Anyway here is a solution for formatting it:
Converting milliseconds to a date (jQuery/JavaScript)

Assuming that Model.PendingTimerEvents is a DateTime, you could just do:
var TimerDate = new Date(#Model.PendingTimerEvents.Year, #Model.PendingTimerEvents.Month, #Model.PendingTimerEvents.Day, #Model.PendingTimerEvents.Hour, #Model.PendingTimerEvents.Minute, #Model.PendingTimerEvents.Second);

You can extract the date with regex if you need to:
<script>
var TimerEvents = #Html.Raw(Json.Encode(Model.PendingTimerEvents)); //"/Date(1521617700000)/"
var dateString = TimerEvents.match(/\d+/)[0] // "1521617700000"
var date = new Date(+dateString); //convert to number
console.log(date); // Wed Mar 21 2018 08:35:00 GMT+0100 (Mitteleuropäische Zeit)
</script>

How to specify timestamp format when converting to human readable string in JS

I need to display a formatted date from a timestamp provided by Google Analytics
Standard solution like
var date = new Date(timestamp * 1000);
var formatted = date.toString();
produces wrong value Jan 01 1970. That's because of timestamp format.
In PHP I can specify the timestamp format:
\DateTime::createFromFormat('Ymd', $timestamp);
How to do this in JS?

Since the dates you are receiving are formatted as YYYYMMDD, not as a Unix
timestamp, you can parse it by
extracting the year, month and date using String.prototype.slice.
var timestamp = '20170306',
year = parseInt(timestamp.slice(0, 4), 10),
month = parseInt(timestamp.slice(5, 6), 10),
day = parseInt(timestamp.slice(7, 8), 10);
// - 1 because the Date constructor expects a 0-based month
date = new Date(Date.UTC(year, month - 1, day)),
gmt = date.toGMTString(),
local = date.toString();
console.log('GMT:', gmt); // Mon, 06 Mar 2017 00:00:00 GMT
console.log('Local:', local);
This assumes that the dates you are using are in UTC (which they likely are). Date.UTC creates a timestamp (in milliseconds since Unix epoch) and then feeds it into new Date() which uses it to create a Date object representing that time. .toGMTString() outputs the date formatted for the GMT timezone. To output it formatted in local time, use .toString() instead.

try this type:
var userDate = new Date();
var day = userDate.getDate();
var month = userDate.getMonth() + 1;
var year = userDate.getFullYear();
alert("Date Formate is :"+year+"-"+month + "-" + day);

In javascript you can use an external library like moment.js
var date = moment.unix(timestamp);
date.format("YYYY MM DD");
See detail about .format here https://momentjs.com/docs/#/displaying/format/

Why is my Date object returning the current date?

I have my time since epoch stored as a number: 1444749469000. However, when I try to convert it to a Date object, using Date(1444749469000), it just gives me the current date instead of the one it should be (around Tue Oct 13 2015).
> Date(1444749469000)
"Tue Apr 12 2016 09:28:30 GMT-0700 (PDT)"

You need a new before the Date because Date is a constructor:
var d = new Date(1444749469000)
alert(d);

Because when you call Date as a function, it will return a string of current date and ignore the given value. In order to retrieve the Date object, you must initialize the Date constructor with keyword new.
var now = Date(1444749469000);
var date = new Date(1444749469000);
console.log(typeof now); //string
console.log(typeof date); //object