react-hook-form/app/src/reValidateMode.tsx

import React from 'react';
import { useParams } from 'react-router-dom';
import { useForm, ValidationMode } from 'react-hook-form';

type ReValidateMode = 'onBlur' | 'onChange' | 'onSubmit' | undefined;
let renderCounter = 0;

const Basic: React.FC = () => {
  const { mode, reValidateMode } = useParams();
  const {
    register,
    handleSubmit,
    formState: { errors },
  } = useForm<{
    firstName: string;
    lastName: string;
  }>({
    mode: mode as keyof ValidationMode,
    reValidateMode: reValidateMode as keyof ReValidateMode,
  });
  const onSubmit = () => {};

  renderCounter++;

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input
        {...register('firstName', { required: true })}
        placeholder="firstName"
      />
      {errors.firstName && <p>firstName error</p>}
      <input
        {...register('lastName', { required: true, maxLength: 5 })}
        placeholder="lastName"
      />
      {errors.lastName && <p>lastName error</p>}
      <button id="submit">Submit</button>
      <div id="renderCount">{renderCounter}</div>
    </form>
  );
};

export default Basic;