CODE EXAMPLE FOR JAVASCRIPT

display month friday 13th javascript year

 function numberOfFridaythe13thsIn(jahr) {
            var counter = 0;
            for (i = 1; i <= 12; i++) {
                var d = new Date(i + "/13/" + jahr);                          
                if (d.getDay() == 5) {
                    counter++;
                }
            }
            return counter;

        }