Using datepicker on another element

Hello,
I’d like to make a new field in booking form on want to use datepicker on it. So I made a custom code on Booking.js in Travel Booking path but it doesn’t work.
So here is my code:

$(‘.datepicker’).datepicker({
dateFormat : ‘mm/dd/yy’,
minDate : date_now
});

I place that code under $(‘input[name=date_book]’).datepicker({…})
What I have missed ? please help me
Thank you.