Formatting dates in JavaScript

JavaScript has own dedicated Date object.  However it does not provide own formatting options so there are plenty of examples available that show different approaches on printing a formatted date.  Here we show one of them covering formatting as ISO8601 string. You may modify this function to fit your own needs:

// Put this function into Function (.user.js) file 
function toISOString(date)
{
    date = date || new Date();
    function pad(number)
    {
        var r = String(number);
        if (r.length === 1)
        {
            r = '0' + r;
        }
        return r;
    }
    return date.getFullYear()
        + '-' + pad(date.getMonth() + 1)
        + '-' + pad(date.getDate())
        + 'T' + pad(date.getHours())
        + ':' + pad(date.getMinutes())
        + ':' + pad(date.getSeconds())
        + '.' + String((date.getMilliseconds() / 1000).toFixed(3)).slice(2, 5)
        + 'Z';
}

1. Print Today's date in ISO8601 format:

// Now you may use it like that:
// Current date:
var today = new Date();
var isoDate = toISOString(today)
Tester.Message("Iso date: " + isoDate);

2. Print Today's date in short format yyyy-mm-dd:

// Short version of the date - cut 1st 10 symbols so we have yyyy-mm-dd:
var today = new Date();
var yyyymmdd= toISOString(today).substring(0, 10);
Tester.Message("yyyymmdd: " + yyyymmdd);

3.  Print specific date:

// Specific date (2015-04-01). 
// Note that month is 0-based, so 0 is Jan, 3 is April.
var someDate = new Date(2015, 3, 1);
Tester.Message("Specific date: " + toISOString(someDate));

4.  Print specific date and time:

// Specific date and time (2012-10-05T20:45). 
// Note that month is 0-based, so 0 is Jan, 3 is April.
var someDateTime = new Date(2012, 9, 5, 20, 45);
Tester.Message("Specific date and time: " + toISOString(someDateTime));