phonepe payment gateway integration

Question

    const makePayment = async (e) => {
    e.preventDefault();
    fetch('/app/api/payment', {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
        }
    })
        .then((response) => response.json())
        .then((data) => {
            console.log(data)
        })
        .catch((error) => {
            console.error(error);
            console.log('Payment response:', data);
        });
}

this payment handler when i click btn then show server error 500 this payment handler when i click btn then show server error 500