Get Number of Days in Any Month of a Year

JavaScript is a programming language used to make web pages interactive without communication with server side. It runs on visitor's computer and client browser interprets and executes it.

JavaScript is having a vast library of functions. We can derive new functions based upon these functions. I am creating a function to calculate total days of a month of any year. Most months have same days in every year but February has either 28/29. That’s why year has importance in this calculation.

The below code snippet shows a HTML page with a text box to input date in format MM/DD/YYYY by user. Second text box shows total number of days on click of a button with label Calculate Days.

There is a JavaScript function GetMonthDays that reads date from input text box, calculates days from month mentioned in input date and shows total days of that month in text box txtDays.

The code or trick to calculate the days in a month is written on line 8.

var calcDate = new Date (inputDate.getFullYear(), inputDate.getMonth()+1, 0);

A date object is created by taking year, month data from date input by user.

The FullYear() method returns four digits year of the specified date.

The getMonth() method returns the month (from 0 to 11) for the specified date.

inputDate.getMonth()+1 passes next month and

0 as a day results in last day of previous month and hence I have a date object with last day of specific month.