JS to modify calendar performance in Booking and Appointment for WooCommerce plugin

main.js

jQuery(document).ready(function ($) {

    if ((0 == $("#booking_calender").length)) {
        return;
    } 

    // Initialize var
    var old_checkout_date = "";
    if ($('#wapbk_hidden_date_checkout').length > 0) {
        old_checkout_date = $('#wapbk_hidden_date_checkout').val();
    }
    
    // Append max rent term notice HTML
    $(".bkap_end_date").before('\
    <div id="max_rent_term_notice" style="font-weight: bold; display: none;">\
        <p>MÁXIMO UNA SEMANA DE ALQUILER</p>\
    </div>');

    // Append negative rent term notice HTML in "My account > Review order" page
    if ($(".woocommerce-view-order").length > 0) { 
        $(".bkap_end_date").before('\
        <div id="negative_rent_term_notice" style="font-weight: bold; display: none;">\
            <p>NO PUEDES INDICAR UNA FECHA ANTERIOR A LA FECHA DE DEVOLUCIÓN ACTUAL</p>\
        </div>');
    }

    $("table.variations tbody select").on('change', function () {
        set_variation_id_before_calculate_price();
        force_one_week_to_booking($(this), old_checkout_date);
    });

    $("#booking_calender").datepicker().on('input change', function () {
        force_one_week_to_booking($(this), old_checkout_date);
    });
    
    $("#booking_calender_checkout").datepicker().on('input change', function () {
        force_one_week_to_booking($(this), old_checkout_date);
    });

    function force_one_week_to_booking(calendar, old_checkout_date) {
        var checkin_class = "#booking_calender";
        var checkout_class = "#booking_calender_checkout";
        var checkin_date = "";
        var checkout_date = "";
        var checkout_date_obj = "";
        var rent_term = "";
        var is_my_account = false;

        // Check if current page is "My account"
        if ($(".woocommerce-view-order").length > 0) {
            var product_id = calendar.closest('.modal-body').attr('id').split('-');
            product_id = product_id[product_id.length-1];
            rent_term = products_data[product_id].tipo_alquiler;
            is_my_account = true;
        } else {
            rent_term = $("select#pa_tipo-alquiler").children("option:selected").val();
        }
        
         // Check if checkin date exist
        if ($(checkin_class).val() === "") {
            return;
        }else {
            checkin_date = $(checkin_class).val();
            // Debug
            console.log( 'checkin_date = ' + checkin_date );
        }
        
        // Check if check out date exist
        if ($(checkout_class).val() === "") {
            return;
        }else {
            checkout_date = $(checkout_class).val();
            //Debug
            console.log( 'checkout_date = ' + checkout_date );
        }
        
        checkin_date = checkin_date.split('/').join('-');
        checkout_date = checkout_date.split('/').join('-');
        var checkin_date_obj = bkap_functions.bkap_create_date_obj(checkin_date);

        $(checkin_class).datepicker("refresh");
        $(checkout_class).datepicker("refresh");
        $("#wapbk_hidden_date").val(checkin_date);

        if (checkout_date.length > 0) {    
            // Clean the notices messages
            $("#max_rent_term_notice").hide();
            $("#negative_rent_term_notice").hide();

            if ('semanas' == rent_term) {
                var days = 0;

                // Calculate the difference days between calendar dates
                if (is_my_account) {
                    days = daysBetween(old_checkout_date, checkout_date);
                } else {
                    days = daysBetween(checkin_date, checkout_date);
                }

                if (days > 0 && days != 7) {
                    days = 7;

                    // Show max rent term notice box
                    $("#max_rent_term_notice").show();    
                } else if (days < 0) {
                    days = 0;

                    // Show negative rent term notice box
                    $("#negative_rent_term_notice").show();
                }

                /**
                 * If user has rescheduled the rent term in My account, then add one week to the previous check out date
                 * instead of to the checkin date
                 */
                if (is_my_account) {
                    checkout_date_obj = bkap_functions.bkap_create_date_obj(old_checkout_date);
                    checkout_date_obj = bkap_functions.bkap_add_days_to_date(checkout_date_obj, days);
                } else {
                    checkout_date_obj = bkap_functions.bkap_add_days_to_date(checkin_date_obj, days);
                }
            } else {
                checkout_date_obj = bkap_functions.bkap_create_date_obj(checkout_date);
            } 
        }
        
        date = bkap_functions.bkap_create_date(checkout_date_obj);
        $("#wapbk_hidden_date_checkout").val(date);
        $(checkout_class).datepicker("setDate", checkout_date_obj);

        if ($("#wapbk_hidden_date").val() !== "" && $("#wapbk_hidden_date_checkout").val() !== "") {
            bkap_calculate_price();

            // Show variation price box
            $("form.variations_form .woocommerce-variation-price").show();
        }
    }

    function set_variation_id_before_calculate_price() {
        var attributes_data = {};
        var rent_type = "";
        var selected_rent_term = $("select#pa_tipo-alquiler").children("option:selected").val();
        var product_variations_data = $("form.variations_form").data('product_variations');

        for (let variation of product_variations_data) {
            if (variation.attributes['attribute_pa_tipo-alquiler'] !== "") {
                rent_type = variation.attributes['attribute_pa_tipo-alquiler'];
                attributes_data[rent_type] = variation.variation_id;
            } else {
                console.log('No existe el atributo: attribute_pa_tipo-alquiler');
            }
        }

        if (selected_rent_term !== "" && attributes_data[selected_rent_term] !== "") {
            $("form.variations_form .variation_id").val(attributes_data[selected_rent_term]);
        }
    }

    // Processing the dates in order to subtract
    function parseDate(str) {
        var mdy = str.split('-');
        return new Date(mdy[2], mdy[1], mdy[0]-1);
    }
    
    // Return the difference days between two dates
    function daysBetween(startDate, endDate) {
        // Take the difference between the dates and divide by milliseconds per day.
        // Round to nearest whole number to deal with DST.
        if (startDate.length == 0 || endDate.length == 0) {
            console.log( 'Error: [function - daysBetween] Al menos una de las fechas está vacía' );
            return false;
        }
        return Math.round((parseDate(endDate) - parseDate(startDate)) / (1000*60*60*24));
    }
});