title: react class method is not defined no-undef
body: <p>I am new in react. My app was running properly, but after adding eslint(airbnb), my apps failed to compile. </p>
  
  <pre><code>export default class HelloWorldComponent extends React.Component {
    render() {
      return (
        &lt;div&gt;
          &lt;div&gt;{this.props.message}&lt;/div&gt;
          &lt;button onClick={this.props.helloWorldClick}&gt;Hello 
          World&lt;/button&gt;
        &lt;/div&gt;
      )
    }
    helloWorldClick = () =&gt; {
      console.log('here') 
    }
  }
  </code></pre>
  
  <p>Before adding { "parser": "babel-eslint" } on .eslintrc file, it was throwing the eslint error </p>
  
  <blockquote>
    <p>"[eslint] Parsing error: Unexpected token =" --on the helloWorldClick arrow function line. </p>
  </blockquote>
  
  <p>After adding parser, i don't have any elsint error. But got compiled error to run the app. </p>
  
  <blockquote>
    <p>Failed to compile
      ./src/component/HelloWorldComponent.js
      Line 18:  'helloWorldClick' is not defined  no-undef</p>
  </blockquote>
  
  <p>Please let me know how can I solve this error. </p>