Building Day Countdown Timer Using JavaScript

Madhanmohan Devarajan
Sep 12, 2016
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In this blog, I have described, how to create a simple count down of days (business days alone) in a page with minimal use of JavaScript and HTML.

JavaScript, given below, has three parts-

The actual timer, which is triggered every 7 milliseconds, so that you can change as per your wish.
myTimerFn() is a function, which sets the start and end dates to get the count down of the business days in between.
The actual function, which provides the count of business days for the given start and end dates.

Code
<html>

<head>
    <script type="text/JavaScript">

        //To call a javascript function using timer (part 1) var myVar = setInterval(myTimerFn, 7000); // To call the pass the start and end date to function calculating the business days in between (part 2) function myTimerFn() { var d = new Date(); var enDate = new Date("09/28/2016"); //alert (d.toISOString() + " | " +enDate.toISOString()); document.getElementById("demo").innerHTML = workingDaysBetweenDates(d.toISOString(),enDate.toISOString()); } //Function for finding business days between two dates (part 3) function workingDaysBetweenDates(stDate, enDate) { var startDate = new Date(stDate); var endDate = new Date(enDate); // Validate input if (endDate
        < startDate) return 0; // Calculate days between dates var millisecondsPerDay=8 6400 * 1000; // Day in milliseconds startDate.setHours(0); // Start just after midnight startDate.setMinutes(0); startDate.setSeconds(0); endDate.setHours(23); // End just before midnight endDate.setMinutes(59); endDate.setSeconds(59); var diff=e ndDate - startDate; // Milliseconds between datetime objects var days=M ath.ceil(diff / millisecondsPerDay); // alert ( "Days Diff:" + days); // Subtract two weekend days for every week in between var weeks=M ath.floor(days / 7); days=d ays - (weeks * 2); // Handle special cases var startDay=s tartDate.getDay(); var endDay=e ndDate.getDay(); // Remove weekend not previously removed. if (startDay - endDay> 1) days = days - 2; // Remove start day if span starts on Sunday but ends before Saturday if (startDay == 0 && endDay != 6) days = days - 1 // Remove end day if span ends on Saturday but starts after Sunday if (endDay == 6 && startDay != 0) days = days - 1 return days; }

    </script>
</head>
<div id="demodiv" style="border:1px solid black;background-color:yellow;height:50px;"><strong><span id="demo"></strong> </span>
    day(s) left </div>

</html>
Output
Please let me know, if you have any issues implementing it.