Question

How can I create a function for finding the number of business days (weekdays) of the current month? Can you code in simple JavaScript without jQuery?

    function daysInMonth(iMonth, iYear)
    {
        return 32 - new Date(iYear, iMonth, 32).getDate();
    }

    function Detail()
    {
        var d = new Date();
        var year = d.getFullYear();
        var month = d.getMonth();
        var dim = daysInMonth(month, year);
        alert(dim);
    }

    function Businessday(iMonth, iYear)
    {
        // Enter code here
    }

    function isBusinessDay()
    {
        var d = new Date();
        var day = d.getDay();
        switch(day) {
            case 0:
                document.write("Today is weekend");
            break;

            case 6:
                document.write("Today is weekend");
                break;

            default:
                document.write("Today is a business day");
        }
    }

Answer 1

OK, let’s solve this one piece at a time.

The Date object in JavaScript has a method, getDay. This will return 0 for Sunday, 1 for Monday, 2 for Tuesday, … 6 for Saturday. Given that, we can conclude that we want to not count days whose getDay returns 0 or 6.

You already have a function to return the number of days in a month, so assuming that, we can loop over all of the days and check the result of getDay. daysInMonth makes the assumption that the month is zero-based; so 0 = January.

I’d encourage you to try solving this on your own from here; otherwise read on.

---

Let’s start with an isWeekday function. We need the year, month, and day:

function isWeekday(year, month, day) {
    var day = new Date(year, month, day).getDay();
    return day !=0 && day !=6;
}

We do exactly as we talked about above: we construct a Date, and use getDay to determine if it’s a day.

Now we need to loop over all of the days in the month:

function getWeekdaysInMonth(month, year) {
    var days = daysInMonth(month, year);
    var weekdays = 0;
    for(var i=0; i< days; i++) {
        if (isWeekday(year, month, i+1))
            weekdays++;
    }
    return weekdays;
}

We loop over all of the days in the month. We add 1 when checking isWeekday because the day, unlike month, is 1 based. If it is, we increment weekdays, then return.

So we can use getWeekdaysInMonth like this:

var weekdays = getWeekdayInMonth(9, 2011); // 9 = October.

Which will result in 21.