JavaScript Program to find leap year or not

This program is for School / College students who are in the beginner level and wants to get a good knowledge in JavaScript.

To find the leap year, below three conditions has to be satisfied,

1. Year should be evenly divisible by 4 (year % 4 == 0)
2. AND (&&) Year should not be evenly divisible by 100 (year % 100 != 0)
3. OR (||) year should be evenly divisible by 400 (Year % 400 == 0)

if both the 1st AND 2nd condition is true OR 3rd is true then it is a Leap year.

Here is the JavaScript function to find leap year:

	function check_leapyear(){
		//define variables
		var year;

		//get the entered year from text box 
		year = document.getElementById("year").value;

		//three conditions to find out the leap year
		if( (0 == year % 4) && (0 != year % 100) || (0 == year % 400) )
		{
			alert(year+" is a leap year");  
		}
		else
		{
			alert(year+" is not a leap year");  
		}
	}

What will you learn from this JavaScript program?

1. You will learn how to get the value of a text box using document.getElementByID()

2. How to use multiple if conditions in a single line

A complete demo program for you to check immediately:

<html>
<head>
<script>
	function check_leapyear(){
		//define variables
		var year;

		//get the entered year from text box 
		year = document.getElementById("year").value;

		//three conditions to find out the leap year
		if( (0 == year % 4) && (0 != year % 100) || (0 == year % 400) )
		{
			alert(year+" is a leap year");  
		}
		else
		{
			alert(year+" is not a leap year");  
		}
	}
</script>
</head>
<body>
<h3>Javascript Program to find leap year</h3>
<input type="text" id="year"></input>
<button onclick="check_leapyear()">Check</button>
<h5>By tutorialsmade.com</h5>
</body>
</html>