在执行fetch post请求时使用react-hook-form和useState时出现问题

import React, { useState } from 'react';
import { useForm } from 'react-hook-form';

const MyForm = () => {
  const { register, handleSubmit, formState: { errors } } = useForm();
  const [formData, setFormData] = useState({});

  const onSubmit = (data) => {
    console.log(data);
    fetch('https://example.com/api', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(data),
    })
    .then(response => response.json())
    .then(data => {
      console.log('Success:', data);
    })
    .catch((error) => {
      console.error('Error:', error);
    });
  };

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input {...register("firstName", { required: true })} />
      {errors.firstName && <span>This field is required</span>}
      <input type="submit" />
    </form>
  );
};

export default MyForm;

const onSubmit = (data) => {
  setFormData(data);
  fetch('https://example.com/api', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify(data),
  })
  .then(response => response.json())
  .then(data => {
    console.log('Success:', data);
  })
  .catch((error) => {
    console.error('Error:', error);
  });
};