const { useForm } = ReactHookForm;

const App = () => {
  const {
    register,
    formState: { isValidating },
    handleSubmit
  } = useForm();

  const onSubmit = (data) => {
    console.log(data);
  };

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input type="text" {...register("email", { required: true })} /> <br />
      <br />
      {isValidating && <p>正在進行驗證...</p>}
      <button type="submit">提交</button>
    </form>
  );
};

ReactDOM.render(<App />, document.querySelector("#app"));