Из за чего на сервере появляется ошибка?

// Forms

    const forms = document.querySelectorAll('form');
    const message = {
        loading: 'img/original.svg',
        success: 'Спасибо! Скоро мы с вами свяжемся',
        failure: 'Что-то пошло не так...'
    };

    forms.forEach(item => {
        bindPostData(item);
    });

    const postData = async (url, data) => {
        const res =  await fetch(url, {
            method: 'POST',
            headers: {
                'Content-type': 'application/json; charset=utf-8'

            },
            body: JSON.stringify(object)
        });

        return await res.json();
    };
    function bindPostData(form) {
        form.addEventListener('submit', (e) => {
            e.preventDefault();
            
            let statusMessage = document.createElement('img');
            statusMessage.src = message.loading;
            statusMessage.style.cssText = `
                display: block;
                margin: 0 auto;
            `;
            form.insertAdjacentElement('afterend', statusMessage);


            // request.setRequestHeader('Content-type', 'application/json');
            const formData = new FormData(form);

            const object = {};
            formData.forEach(function (value, key) {
                object[key] = value;
            });


            postData('http://localhost:3000/requests', JSON.stringify(object))
                .then(data => {
                    console.log(data);
                    showThanksModal(message.success);
                    statusMessage.remove();
                })
                .catch(() => {
                    showThanksModal(message.failure);
                })
                .finally(() => {
                    form.reset();
                });
        });
    }

    function showThanksModal(message) {
        const prevModalDialog = document.querySelector('.modal__dialog');

        prevModalDialog.classList.add('hide');
        openModal();

        const thanksModal = document.createElement('div');
        thanksModal.classList.add('modal__dialog');
        thanksModal.innerHTML = `
            <div class="modal__content">
                <div class="modal__close" data-close>×</div>
                <div class="modal__title">${message}</div>
            </div>
        `;
        document.querySelector('.modal').append(thanksModal);
        setTimeout(() => {
            thanksModal.remove();
            prevModalDialog.classList.add('show');
            prevModalDialog.classList.remove('hide');
            closeModal();
        }, 4000);
    }

    fetch('db.json')
        .then(data => data.json())
        .then(res => console.log(res));
});

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 150px;
    padding: 0 100px
}

.header__left-block {
    display: flex;
    justify-content: space-between;
    min-width: 550px
}

.header__logo {
    max-width: 170px
}

.header__logo img {
    width: 100%
}

.header__links {
    display: flex;
    align-items: center
}

.header__link {
    position: relative;
    margin-right: 45px;
    font-weight: 700;
    font-size: 18px;
    color: #303030
}

.header__link:after {
    content: '';
    position: absolute;
    display: block;
    width: 110%;
    left: -5%;
    bottom: -1px;
    z-index: -1;
    height: 8px;
    background: #54ed39
}

.header__link:last-child {
    margin-right: 0
}

.sidepanel {
    position: fixed;
    left: 60px;
    top: 240px;
    height: 400px;
    width: 25px;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    align-items: center
}

<header class="header">
        <div class="header__left-block">
            <div class="header__logo">
                <img src="icons/logo.svg" alt="Логотип">
            </div>
            <nav class="header__links">
                <a href="#" class="header__link">Доставка питания</a>
                <a href="#" class="header__link">Второй пункт</a>
            </nav>
        </div>
        <div class="header__right-block">
            <button class="btn btn_white" data-modal>Связаться с нами</button>
        </div>
    </header>