Enable single day in calendar

Question

I'm trying to enable a single day in the calendar, but I'm getting an error.

<script>
var nomersw = 'data_decore';
if(jQuery('input[name="'+nomersw+'"]')){
   $(function(){
    $("input").datepicker(
        {
        beforeShowDay: function (date) {
        if (date.getDate() == 11 ) {
            return [true, ''];
        }
        return [false, ''];
        }
        }

    );
}); 
</script>  

Observation:

nomersw is in the datepicker name in the form

I appreciate if any colleagues point out the errors in the code.