How to validate Braintree cardholder name input in react.js

Question

I integrated drop-in ui from briantree in my react project. But I don´t know how to validate the inputs. I want only letters can be written in the cardholder name input, because currently it accepts numbers as well.

const handleOnClick = () => {
    if (braintreeInstance) {
      braintreeInstance.requestPaymentMethod((error, payload) => {
        if (error) {
          toast.error("Error");
        }

        if (/^[0-9]*$/.test(payload.details.cardholderName)) {
          console.log("Invalid name", payload.details.cardholderName);
       
        } else {
          const paymentMethodNonce = payload.nonce;
          console.log("braintreeInstance", payload);
          onPaymentCompleted(paymentMethodNonce);
        }
      });
    }
  };