drinks-manager/static/js/order.js

document.addEventListener("DOMContentLoaded", () => {

    // elements

    let order_number_of_drinks_input = document.getElementById("numberOfDrinks");
    let order_number_of_drinks_btn_a = document.getElementById("numberOfDrinksBtnA");
    let order_number_of_drinks_btn_b = document.getElementById("numberOfDrinksBtnB");
    let order_sum_element = document.getElementById("orderCalculatedSum");

    let order_form = document.getElementById("orderForm");
    let status_info = document.getElementById("statusInfo");
    let order_submit_button = document.getElementById("orderSubmitBtn");


    // calculate & display sum

    let order_price_per_drink = parseFloat(document.getElementById("pricePerDrink").dataset.drinkPrice.replace(",", "."));

    function calculate_and_display_sum() {

        setTimeout(() => {

            let number_of_drinks = parseFloat(order_number_of_drinks_input.value);
            let calculated_sum = order_price_per_drink * number_of_drinks;
            order_sum_element.innerText = new Intl.NumberFormat(undefined, {minimumFractionDigits: 2}).format(calculated_sum);

        }, 25);

    }

    order_number_of_drinks_input.addEventListener("input", calculate_and_display_sum);
    order_number_of_drinks_btn_a.addEventListener("click", calculate_and_display_sum);
    order_number_of_drinks_btn_b.addEventListener("click", calculate_and_display_sum);


    // custom submit method

    order_form.addEventListener("submit", (event) => {

        order_submit_button.disabled = true;

        event.preventDefault(); // Don't do the default submit action!

        let xhr = new XMLHttpRequest();
        let formData = new FormData(order_form);

        xhr.addEventListener("load", (event) => {

            status_ = event.target.status;
            response_ = event.target.responseText;

            if (status_ == 200 && response_ == "success") {
                status_info.innerText = "Success.";
                window.location.replace("/");
            }
            else {
                status_info.classList.add("errorText");
                status_info.innerText = "An error occured.";
                window.setTimeout(() => { window.location.reload() }, 5000);
            }

        })

        xhr.addEventListener("error", (event) => {
            status_info.classList.add("errorText");
            status_info.innerText = "An error occured.";
            window.setTimeout(() => { window.location.reload() }, 5000);
        })

        xhr.open("POST", "/api/order-drink");
        xhr.send(formData);

    });

})