How to get day of week from specific date in JavaScript

Table of Contents

Understanding Date and Time in JavaScript

Date and time are essential concepts in programming. In JavaScript, the Date object is used to work with dates and times. It allows us to create, manipulate, and format dates and times. Here are some important things to know about the Date object in JavaScript:

The Date object represents a specific moment in time.
The Date object is created using the new keyword followed by the Date constructor.
The Date object stores dates as the number of milliseconds since January 1, 1970, 00:00:00 UTC.
The Date object can be formatted using various methods, including toLocaleDateString(), toLocaleTimeString(), and toLocaleString().
The Date object also includes methods for working with individual date and time components, such as getFullYear(), getMonth(), getDate(), getHours(), getMinutes(), and getSeconds().

Understanding how to work with dates and times in JavaScript is essential for any web developer. By using the Date object, we can perform various operations, such as calculating intervals between dates, displaying dates and times in a user-friendly format, and working with timezones.

JavaScript’s Built-In Date Object

The Date object in JavaScript is a built-in object and it represents a single moment in time. It allows you to work with dates and times in your JavaScript code. You can create a new instance of the Date object using the new keyword, followed by the Date constructor:

var today = new Date();

Once you have a Date object, you can use its methods to get different parts of the date and time, such as the year, month, day, hours, minutes, seconds, and milliseconds:

var year = today.getFullYear();
var month = today.getMonth();
var day = today.getDate();
var hours = today.getHours();
var minutes = today.getMinutes();
var seconds = today.getSeconds();
var milliseconds = today.getMilliseconds();

One common use case for the Date object is to get the day of the week for a specific date. You can do this by using the getDay() method, which returns an integer between 0 and 6, where 0 represents Sunday, 1 represents Monday, and so on:

var date = new Date('2021-12-01');
var dayOfWeek = date.getDay(); // 3 (Wednesday)

In the example above, we create a new Date object for December 1st, 2021, and then use the getDay() method to get the day of the week, which is 3 (Wednesday).

Overall, the Date object in JavaScript provides a lot of useful functionality for working with dates and times in your code.

Extracting Day of the Week from a Date Object in JavaScript

One common task when working with dates in JavaScript is extracting the day of the week from a given date object. Fortunately, JavaScript provides a built-in method for doing just that. The getDay() method is available on Date objects and returns the day of the week as a number, where Sunday is 0, Monday is 1, and so on. To get the day of the week as a string, you can use an array of weekday names and use the returned number to index into the array.

Here’s an example of how to use the getDay() method to extract the day of the week from a date object:

const date = new Date('2022-08-25'); 
const weekdayNames = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']; 
const weekdayIndex = date.getDay(); 
const weekdayName = weekdayNames[weekdayIndex]; 
console.log(`The day of the week for ${date} is ${weekdayName}.`);

This code creates a new date object representing August 25, 2022 and then uses getDay() to get the weekday index (which is 4, for Thursday).

It then uses the weekdayNames array to get the corresponding weekday name (which is ‘Thursday’, in this case) and logs a message to the console. In summary, extracting the day of the week from a date object in JavaScript is a simple task thanks to the built-in getDay() method.

Converting Day of the Week to a More Readable Format

Converting the day of the week from a specific date in JavaScript is a useful tool for many applications. However, the resulting day may be displayed in an abbreviated format (e.g. “Fri” for Friday) or in a format that is not easily readable by humans (“3” for Wednesday). Here, we will explore how to convert the day of the week from a specific date into a more readable format.

One approach to achieve a more readable format is to create an array containing the names of the days of the week. Then, the day of the week can be represented by an index in the array. For example:

const daysOfWeek = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
const date = new Date();
const dayOfWeekIndex = date.getDay(); // returns a number between 0 and 6
const dayOfWeek = daysOfWeek[dayOfWeekIndex];
console.log(dayOfWeek); // "Wednesday"

In the example above, we first create an array containing the names of the days of the week. Then, we use the Date.getDay() method to get the day of the week as a number between 0 and 6 (0 being Sunday and 6 being Saturday). Finally, we retrieve the name of the day of the week using the index obtained from getDay().

By using this method, we can easily display the day of the week in a more readable format without relying on abbreviations or numeric representations. This can be especially useful for applications that require user-friendly interfaces or for displaying dates in written form.

Handling Timezone Differences When Calculating Day of the Week in JavaScript

Calculating the day of the week for a specific date can easily be done in JavaScript using the built-in Date object. However, when dealing with users or systems in different timezones, it is important to take those differences into account.

One crucial step to handle timezone differences is to ensure that the date object is created using the user’s or system’s timezone instead of the server’s timezone. This can be done by either getting the user’s timezone offset or by using a library like Moment.js to handle the timezone conversion.

Another important consideration is to take into account daylight saving time changes. In some locales, the daylight saving time changes occur at midnight, which can cause unexpected results if not handled properly.

One way to handle daylight saving time changes is to adjust the date and time based on the local timezone offset. By doing this, the timezone offset takes into account any daylight saving time changes that may occur on that specific date.

In summary, when calculating the day of the week in JavaScript while handling timezone differences, it is important to:

Create the date object using the user’s or system’s timezone
Handle daylight saving time changes properly

Dealing with Leap Years in JavaScript When Calculating Day of the Week

When calculating the day of the week in JavaScript, it’s important to take into account leap years. Leap years add an extra day to the calendar year, which means that the number of days in a year can vary. This, in turn, affects how the day of the week is calculated.

In JavaScript, you can use the built-in Date object to calculate the day of the week for a specific date. However, if the date is in a leap year, you need to make some adjustments to the calculation.

One way to deal with leap years is to first calculate the total number of days that have passed between the current date and a reference date, such as January 1st. Then, you can add the number of days in each month to get the total number of days in the year, taking into account the extra day in a leap year. Finally, you can divide the total number of days by 7 and use the remainder to determine the day of the week.

For example, if the reference date is January 1st and the current date is February 28th in a leap year, the calculation would be as follows:

// Calculate total number of days
let totalDays = (date.getTime() - referenceDate.getTime()) / (1000 * 60 * 60 * 24);

// Add number of days in each month, taking into account leap year
totalDays += 31; // January
totalDays += 29; // February (leap year)
totalDays += 31; // March

// Divide total number of days by 7 and use remainder to determine day of week
let dayOfWeek = totalDays % 7;

By taking into account leap years in your JavaScript calculations, you can accurately determine the day of the week for any given date.

Putting It All Together: Examples of Getting Day of the Week from Specific Dates in JavaScript

Once you have understood the basic concepts and methods to get the day of the week from a specific date in JavaScript, you can put it all together to use it in real-world scenarios. Here are a few examples:

Example 1: Displaying the Day of the Week on a Web Page

Let’s say you want to display the day of the week on your web page for a specific date entered by the user. You can use the following code.

const dateStr = "2022-05-01"; // date entered by the user 
const days = ['Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday']; 
const date = new Date(dateStr); // create a new date object 
const dayOfWeek = days[date.getDay()]; // get the day of the week

document.getElementById("result").innerHTML = `The day of the week for ${dateStr} is ${dayOfWeek}.`;

Here, we create a new date object using the date string entered by the user. We then use the `getDay()` method to get the day of the week as a number (0 for Sunday, 1 for Monday, and so on). We then use an array of weekday names to get the actual name of the day of the week. Finally, we display the result on the web page using the `innerHTML` property of an HTML element with the ID “result”.

Example 2: Highlighting Weekends in a Calendar

Let’s say you have a calendar on your web page and you want to highlight weekends in a different color. You can use the following code.

const days = ['Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday']; 
const cells = document.querySelectorAll(".calendar-cell"); // get all cells in the calendar 
cells.forEach(cell => { const dateStr = cell.dataset.date; // get the date from a data attribute 
const date = new Date(dateStr); // create a new date object 
const dayOfWeek = date.getDay(); // get the day of the week 
if(dayOfWeek === 0 || dayOfWeek === 6) 
{ // if Sunday or Saturday 
cell.classList.add("weekend"); 
// add the "weekend" class to the cell 
};

Here, we first define an array of weekday names and get all cells in the calendar using the `querySelectorAll()` method. We then loop through all cells and get the date from a custom data attribute using the `dataset` property.

We create a new date object and get the day of the week as a number. If the day of the week is Sunday (0) or Saturday (6), we add the “weekend” class to the cell using the `classList.add()` method. You can then define the “weekend” class in your CSS to give it a different color or style.

These are just a few examples of how you can use the methods to get the day of the week from a specific date in JavaScript. With a little bit of creativity, you can use these methods to solve various real-world problems.

How to get day of week from specific date in JavaScript?