Javascript Closure “creating Local variable for the callback function”

Question

I am using javascript DatPicker like

datefield = $('fromdate');

datepicker = new DatePicker(wrapper, 
   {months:1
   , onSelect: function(datefield) {
                 return function() {
                   onDatePick();
                 } 
               }( datefield ) 
    });

where onSelect is a callback function which will be called when the user clicks on a Date. and DatePicker passed the Selected Date as Callback function's argument. This Date will be written in the datefield input field.

I thought that within the closoure this field will be avialble as local variable, but it is always undefined.

Answer 1

to add parameter to callback function, you need to do something like this:

datefield = $('fromdate');
datepicker = new DatePicker(wrapper, 
   {months:1
   , onSelect: (function(datefield) {
                 return function() {
                   onDatePick();
                 } 
               }) (datefield) 
    });