Javascript:Date

Without an argument, we have seen that the new Date() constructor

returns the current date and time. But it returns a long date-time

representation.

e.g.

const date = new Date();

we can use methods like getFullYear(), getMonth(), and getDate() to

get the current year, month, and date, respectively.It is important

to note that getMonth() return month in 0 based index so to get actual

month ,we need to add 1 to its value.

e.g.

let fullYear = date.getFullYear();

let month = date.getMonth() +1;

let day = date.getDate();

The Date.now() static method returns the current timestamp in milliseconds.

This is the local time elapsed since the epoch.

e.g.

let dt = Date.now()

Date constructor can create a Date object by passing the timestamp milliseconds

as an argument. Hence, we can pass the Date.now() to the Date constructor to

get the current date and time.

e.g.

let dtNow = new Date(Date.now())

The toJSON() method of the Date object returns the current date and time in

the date time string format. That is YYYY-MM-DDTHH:mm:ss.sssZ.

e.g.

let dtJson = new Date().toJSON();

To extract only date part from datetime we use slice() on toJSON(),date

returned is in format YYYY-MM-DD

e.g.

let dateOnly =new Date().toJSON().slice(0, 10);

toLocaleDateString() method:

To get the current date into a JavaScript string we use

toLocalDateString() method from the Date object.

e.g.

const date = new Date().toLocaleDateString();

You can pass the locale as an argument to the toLocalDateString()

method to get a locale-specific date. For example, to get the current

date in the German locale, you can pass de-DE as the argument.

e.g.

const date = new Date().toLocaleDateString("de-DE");

To get in indian format we should use

e.g.

const dateByLocalization = new Date().toLocaleDateString("en-IN");

How to find time elapsed using the JavaScript Date Object ?

difference between two date can be obtained by substracting one from

other,we get diference in milliseconds.

const startDate = new Date('2023-08-15T00:00:00');

const endDate = Date.now(); // Current date and time in milliseconds

// Calculate the time difference in milliseconds

const timeDifferenceMS = endDate - startDate;

console.log("Time Difference in MilliSeconds",timeDifferenceMS)

Date Formatting:

ECMAScript provide Intl.DateTimeFormat to format date.

e.g.

const date001 = new Date(Date.UTC(2023, 9, 17, 13, 1, 0));

console.log(new Intl.DateTimeFormat().format(date001));

Output:

17/10/2023

Here we are passing month as 9 but getting 10 as months is zero

based index in javascript.

To Intl.DateTimeFormat we can pass parameter which will tell which

local to be used.

e.g.

const date002 = new Date(Date.UTC(2013, 09, 17, 13, 10, 20));

console.log("In en-US: ", new Intl.DateTimeFormat("en-US")

.format(date002));

It is possible to pass options as parameter to function

Intl.DateTimeFormat

e.g.

// request a weekday along with a long date

let options = {

weekday: "long",

year: "numeric",

month: "long",

day: "numeric",

};

console.log(new Intl.DateTimeFormat("en-US", options)

.format(date003));

Output:

Tuesday, October 17, 2023

Third Party Date Library:

date-fns: date-fns is a modern JavaScript date utility library that

provides a wide range of functions for formatting, parsing,

manipulating, and comparing dates and times. It emphasizes simplicity

and immutability.

Moment.js was one of the most popular date libraries in the JavaScript

ecosystem. It provides a comprehensive set of date manipulation and

formatting functions.However, as of September 2020, it has been

considered legacy.