jquery ui calendar load events on page load

So, I have the days loaded in calendar with solution from my previous question

code here for clarity

$("#datepicker").datepicker({
    firstDay: 1,
    dateFormat: "yy-mm-dd",
    minDate: minDate,
    beforeShowDay: function (date) {

        var month = (date.getMonth() + 1).toString().padStart(2, "0");
        var year = date.getFullYear();
        var day = date.getDate().toString().padStart(2, "0");

        // Change format of date
        var newdate = year + "-" + month + '-' + day + 'T00:00:00';
        // Check date in Array
        if (jQuery.inArray(newdate, unavDates) != -1) {
            return [true, "available"];
        }
        else{
            return [false, "unavailable"];
        }
        if (date.getDay() === 0 || date.getDay() === 6 || date.getDay() === 1 || date.getDay() === 5){
            return false;
        }

        return [true];
    },

});

but the problem I have is that the function is triggered by a click on a day in calendar. How do I make it available on page load?