How to get the number of days in a specified month using JavaScript ?

Given a month and the task is to determine the number of days of that month using JavaScript.

JavaScript getDate() Method: This method returns the number of days in a month (from 1 to 31) for the defined date.

Syntax:
```
Date.getDate()
```
Return value: It returns a number, from 1 to 31, representing the day of the month.
JavaScript getFullYear() Method: This method returns the year (four digits for dates between year 1000 and 9999) of the defined date.
Syntax:
```
Date.getFullYear()
```
Return value: It returns a number, representing the year of the defined date
JavaScript getMonth() Method: This method returns the month (from 0 to 11) for the defined date, based on to local time.
Syntax:
```
Date.getMonth()
```
Return value: It returns a number, from 0 to 11, representing the month.

Example 1: This example gets the days in the month (february) of the year (2020) by passing the month (1-12) and year to the function daysInMonth.

<!DOCTYPE HTML>  
<html>  
    <head>  
        <title>  
            Get number of days in 
            a specified month 
        </title>      
    </head>  
      
    <body style = "text-align:center;"> 
           
        <h1 style = "color:green;" >  
            GeeksForGeeks  
        </h1> 
          
        <p id = "GFG_UP" style = 
            "font-size: 15px; font-weight: bold;"> 
        </p> 
          
        <button onclick = "GFG_Fun()"> 
            click here 
        </button> 
          
        <p id = "GFG_DOWN" style = 
            "color:green; font-size: 20px; font-weight: bold;"> 
        </p> 
          
        <script> 
            var up = document.getElementById('GFG_UP'); 
              
            up.innerHTML = "Click on button to get the" 
                + " number of days in specified month"; 
                  
            var down = document.getElementById('GFG_DOWN');  
              
            function daysInMonth (month, year) { 
                return new Date(year, month, 0).getDate(); 
            } 
              
            function GFG_Fun() { 
                var date = new Date(); 
                var month = 2; 
                var year = 2020; 
                down.innerHTML = "Number of days in " + month 
                             + "nd month of the year " + year 
                             +" is "+ daysInMonth(month, year); 
            } 
        </script>  
    </body>  
</html>                     

Output:

Before clicking on the button:
After clicking on the button:

Example 2: This example gets the days in the current month of the current year by passing the month (1-12) and year to the function daysInMonth.

<!DOCTYPE HTML>  
<html>  
    <head>  
        <title>  
            Get number of days in a specified month 
        </title>      
    </head>  
      
    <body style = "text-align:center;">  
      
        <h1 style = "color:green;" >  
            GeeksForGeeks  
        </h1> 
          
        <p id = "GFG_UP" style =  
            "font-size: 15px; font-weight: bold;"> 
        </p> 
          
        <button onclick = "GFG_Fun()"> 
            click here 
        </button> 
          
        <p id = "GFG_DOWN" style =  
            "color:green; font-size: 20px; font-weight: bold;"> 
        </p> 
          
        <script> 
            var up = document.getElementById('GFG_UP'); 
              
            up.innerHTML = "Click on button to get the number" 
                    + " of days in specified month"; 
              
            var down = document.getElementById('GFG_DOWN');  
              
            function daysInMonth (month, year) { 
                return new Date(year, month, 0).getDate(); 
            } 
              
            function GFG_Fun() { 
                var date = new Date(); 
                var month = date.getMonth() + 1; 
                var year = date.getFullYear(); 
                down.innerHTML = "Number of days in " + month 
                            + "th month of the year " + year  
                            +" is "+ daysInMonth(month, year); 
            } 
        </script>  
    </body>  
</html>                     

Output:

Before clicking on the button:
After clicking on the button:

My Personal Notes

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