title: State is not defined no-undef ReactJS?
body: <p>So I keep getting the error <code>Line 29:  'answers' is not defined  no-undef</code> and I am not quite sure what's going on or how to fix it (I'm very new to React and JS). Could anyone perhaps explain what this means and give me a few pointers? Thanks!</p>
  
  <pre><code>class App extends Component {
  
  
    constructor(props){
      super(props);
        this.state = {
          key: myUUID,
          title: "",
          author: "",
          questions: [],
          answers: []
        }
    }
  
    addQuestion(){
      questionNum++;
      this.setState({
        answers }, () =&gt; {
        this.state.answers.concat("hello")
      });
    }
  </code></pre>
  
  <p>UPDATE: Here's what the new <code>addQuestion</code> function looks like </p>
  
  <pre><code>  addQuestion(){
      questionNum++;
      this.setState({
        answers: this.state.answers.concat("hello")
      });
    }
  </code></pre>
  
  <p>I call this function when this button is clicked <code>&lt;button onClick={this.addQuestion}&gt;Add Question&lt;/button&gt;</code></p>
  
  <p>Now I am getting this error <code>TypeError: Cannot read property 'setState' of undefined</code></p>