JetBooking. Allow booking only with fixed date range based on the post meta

jet-booking-fixed-dates.php

<?php
add_action( 'wp_footer', function() {
	$days_to_book = get_post_meta( get_the_ID(), 'booking_duration' );
	
	if ( ! $days_to_book ) {
		$days_to_book = 1;
	}
	
	$days_to_book = $days_to_book - 1;
?>
<script>
	var jetBookingDaysNum = <?php echo $days_to_book; ?>;
	jQuery( document ).on( "jet-booking/init-field", ( $event, $field ) => {
		$field.bind( "datepicker-first-date-selected", ( event, obj ) => {
			$field.data( "dateRangePicker" ).setEnd( moment( obj.date1 ).add( jetBookingDaysNum, "d" ).format( "YYYY-MM-DD" ) );
		} );
	} );
</script>
<?php
}, 99 );