react-hook-form 7.42.0-next.0

Version 7.42.0-next.0

on Node.js Yarn

type FormValues = {
  number1: number;
  number2: number;
};

// Making exported validate function isolated for validation
export function validateNumber(_: number, formValus: FormValues) {
  return formValus.number1 + formValus.number2 === 3;
}

export default function App() {
  const { register, handleSubmit } = useForm({
    defaultValues: {
      number1: 0,
      number2: 0
    }
  });

  return (
    <form onSubmit={handleSubmit((data) => console.log(data))}>
      <input
        type="number"
        {...register("number1", {
          validate: validateNumber,
          valueAsNumber: true
        })}
      />
      <input
        type="number"
        {...register("number2", {
          validate: validateNumber,
          valueAsNumber: true
        })}
      />
     <button>submit</button>
    </form>
  );
}