JavaScript program to check if a given year is leap year Javascript判断是否是闰年

Before input year: <img src="https://media.geeksforgeeks.org/wp-content/uploads/20190402112744/leap1.png" alt="" class="aligncenter size-medium wp-image-983529 medium-zoom-image">
After input leap year: <img src="https://media.geeksforgeeks.org/wp-content/uploads/20190402112745/leap2.png" alt="" class="aligncenter size-medium wp-image-983530 medium-zoom-image">
After input not leap year: <img src="https://media.geeksforgeeks.org/wp-content/uploads/20190402112746/leap3.png" alt="" class="aligncenter size-medium wp-image-983531 medium-zoom-image">

A year is leap year if following conditions are satisfied:

Year is multiple of 400.
Year is multiple of 4 and not multiple of 100.

Approach:

Get the value of input field by using document.getElementById(“year”).value
Check the given year is leap year or not by using JavaScript expression and display its value.

Example:

<!-- HTML code to implement the given year is 
    leap year or not -->
<!DOCTYPE html>
<html>
  
<head>
    <title>
        JavaScript to check leap year
    </title>
</head>
  
<body>
    Input Year: <input type="text" id = "year"/>
      
    <input type="button" id="button" onClick="isLeapYear()"
            value="Check Leap Year">
      
    <p id="GFG"></p>
      
    <!-- JavaScript code to check given year is
        leap year or not -->
    <script>
        function isLeapYear() {
            var year= document.getElementById("year").value;
              
            document.getElementById("GFG").innerHTML 
                = (year % 100 === 0) ? (year % 400 === 0)
                                     : (year % 4 === 0);
        }
    </script>
</body>
  
</html>                    