CustomTextareaInput.js

class CustomTextInput extends React.Component<{}> {

  handleSubmit = e => {
    e.preventDefault();
    console.log(this.textInput);
  };


  // tell Flow that we want to associate the textInput ref
  // with an HTML Input button
  textInput: ?HTMLInputElement;

  render() {
    return (
      <div>
        <form onSubmit={e => this.handleSubmit(e)}>
          <textarea ref={textInput => (this.textInput = textInput)} />
          <button>Submit</button>
        </form>
      </div>
    );
  }
}