JavaScript: Get the number of days in a month

JavaScript Datetime: Exercise-3 with Solution

Days in Month

Write a JavaScript function to get the number of days in a month.

Test Data:
console.log(getDaysInMonth(1, 2012));
console.log(getDaysInMonth(2, 2012));
console.log(getDaysInMonth(9, 2012));
console.log(getDaysInMonth(12, 2012));
Output :
31
29
30
31

Sample Solution:

JavaScript Code:

// Define a JavaScript function called getDaysInMonth with parameters month and year
var getDaysInMonth = function(month, year) {
  // Get the number of days in the specified month and year
  return new Date(year, month, 0).getDate();
  // Here January is 0 based
  // return new Date(year, month+1, 0).getDate();
};

// Output the number of days in January 2012
console.log(getDaysInMonth(1, 2012));
// Output the number of days in February 2012
console.log(getDaysInMonth(2, 2012));
// Output the number of days in September 2012
console.log(getDaysInMonth(9, 2012));
// Output the number of days in December 2012
console.log(getDaysInMonth(12, 2012));

Output:

31
29
30
31

Explanation:

In the exercise above -

• The code defines a JavaScript function named "getDaysInMonth()" with two parameters: 'month' and 'year'. This function is intended to calculate the number of days in a specific month of a given year.
• Inside the function:
• It creates a new Date object using the provided 'year' and 'month' parameters. The 'month' parameter is 1-based, where January is represented by 1.
• By setting the day parameter to 0 in the Date constructor, it gets the last day of the previous month, effectively representing the last day of the specified month.
• It then calls .getDate() on this Date object to retrieve the day component, which corresponds to the total number of days in the specified month.
• The function returns the calculated number of days.
• The code then provides several test cases using console.log() to output the results of calling the "getDaysInMonth()" function with different month and year combinations:
• January 2012
• February 2012 (leap year)
• September 2012
• December 2012

Flowchart:

Live Demo:

See the Pen JavaScript - Get the number of days in a month-date-ex- 3 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that calculates the number of days in a specified month by creating a Date for the next month and subtracting one day.
• Write a JavaScript function that returns 29 for February if the given year is a leap year, otherwise 28.
• Write a JavaScript function that accepts month and year parameters, validates them, and returns the correct number of days.
• Write a JavaScript function that uses the Date object to determine the number of days in each month and tests all 12 months.

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