Find how many Sundays fell on the first of the month for a given year using JavaScript — Programming Interview Questions.

Write a program to determine how many Sundays fell on the first of the month for a given year.

We’ll go through the first of every month in a year and check if it’s a Sunday. We’ll use a counter and keep incrementing the counter whenever we find a Sunday.

Implementation using JavaScript:

We first need to find out the day of any given date in JavaScript. This is because JavaScript uses a built-in Date object that implements getDay — that for a specific date returns the day of the week.

Example:

const mydate = new Date('November 30, 2021 23:15:30');
const day1 = mydate.getDay();
console.log(day1);
OUTPUT: 2

It represents Sunday to Saturday, starting from 0 till 6, i.e. it is a Sunday when getDay returns 0.

Thus, we’ll just iterate over 1st of all the months in the given year and store the number of Sundays in a counter variable.

function numSundaysOnFirst(year) {
   let sundays = 0;
   
   for (let month = 1; month <= 12; month++) {
     if (new Date(year, month, 1).getDay() === 0) {
         sundays++;
     }
   }
   return sundays;
}

That’s all.
You can also practice a slight variation of this problem on the HackerRank platform here.

Reference to other programming questions —
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