CODE EXAMPLE FOR JAVASCRIPT

javascript get current week number

function weekNumber(date = new Date())
{
  var firstJanuary = new Date(date.getFullYear(), 0, 1);
  var dayNr = Math.ceil((date - firstJanuary) / (24 * 60 * 60 * 1000));
  var weekNr = Math.ceil((dayNr + firstJanuary.getDay()) / 7);
  return weekNr;
}