jQuery Forum

This will alert the week number:

1.         $( "#pickdate" ).datepicker({
               onSelect: function(dateText, inst) {alert($.datepicker.iso8601Week(new Date(dateText)))}
           });
        
   

I think the calculateWeek option allows you to define a different week calculation than the default one, rather than actually generate a week number.                                                                                                                                                                                                    

To get the formatted value try this:

1. $('#datepicker').datepicker({..., onSelect(dateStr) {
2.       var date = $(this).datepicker('getDate');
3.       var week = (!date ? 0 : $.datepicker.iso8601Week(date));
4.       $('#week').val(!date ? '' : date.getFullYear() + '-' + (week < 10 ? '0' : '') + week);
5. });

Thanks for both of your answers!

1. $('#datepicker').datepicker({
2.                     onSelect: function(dat,inst){
3.                         var week=$.datepicker.iso8601Week(new Date(dat));
4.                         $('#datepicker').val($.datepicker.formatDate('yy-',new Date(dat))+(week<10?'0':'')+week)
5.                     }
6. });

I think it would be handy if jQuery had the option in dateFormat to add "w" and "ww" for week of year and week of year with leading zero.