<!-- BEGIN COPY / PASTE -->
    import React from 'react';
    import { useForm } from 'react-hook-form';

    function MyForm() {
      const { register, handleSubmit, formState: { errors } } = useForm();
      const onSubmit = data => console.log(data);

      return (
        <form onSubmit={handleSubmit(onSubmit)}>
          <input {...register('username', { required: true })} placeholder="Username" />
          {errors.username && <span>This field is required</span>}
          <input type="submit" />
        </form>
      );
    }
    <!-- END COPY / PASTE -->