Validate number of days in a given month

Question

Performance is of the utmost importance on this one guys... This thing needs to be lightning fast!


How would you validate the number of days in a given mont

Answer 1

all this logic is already built in to the javascript engine... Why recode it ? Unless you are doing this just as an exercise, you can use the javascript Date object:

Like this:

function daysInMonth(aDate) {
      return new Date(aDate.getYear(), aDate.getMonth()+1, 0).getDate();      
   }

Answer 2

Assuming the JS Date object standard where months are numbered from 0, and you have your daysInMonth array:

var days = daysInMonth[month] + ((month === 1) && (year % 4 === 0) && ((year % 100 !== 0) || (year % 400 === 0)));

will give you the number of days in the month, with 28 increased to 29 iff the month is February and the year is a leap year.

Answer 3

You can use DateTime to solve this:

new DateTime('20090901')->format('t'); // gives the days of the month

Answer 4

Moment.js

Have you tried moment.js?

The validation is quite easy to use:

var m = moment("2015-11-32");
m.isValid(); // false

I don't know about the performances but hum the project is stared 11,000+ times on GitHub (kind of a quality guarantee).

Source: http://momentjs.com/docs/#/parsing/is-valid/

Answer 5

function caldays(m,y)
{
    if (m == 01 || m == 03 || m == 05 || m == 07 || m == 08 || m == 10 || m == 12)
    {
        return 31;              
    }
    else if (m == 04 || m == 06 || m == 09 || m == 11)
    {
        return 30;        
    }
    else
    {    
        if ((y % 4 == 0) || (y % 400 == 0 && y % 100 != 0))
        {    
            return 29;          
        }
        else 
        {
            return 28;              
        }
    }    
}

source: http://www.dotnetspider.com/resources/20979-Javascript-code-get-number-days-perticuler-month-year.aspx

Answer 6

This will not perform as well as the accepted answer. I threw this in here because I think it is the simplest code. Most people would not need to optimize this function.

function validateDaysInMonth(year, month, day)
{
    if (day < 1 || day > 31 || (new Date(year, month, day)).getMonth() != month)
        throw new Error("Frack!");
}

It takes advantage of the fact that the javascript Date constructor will perform date arithmetic on dates that are out of range, e.g., if you do:

var year = 2001; //not a leap year!
var month = 1 //February
var day = 29; //not a valid date for this year
new Date(year, month, day);

the object will return Mar 1st, 2001 as the date.