title: Giving React component animation on mount
body: <p>I am trying to make this component move in when mounted but getting</p>
  
  <pre><code>Cannot read property 'enter' of undefined
  </code></pre>
  
  <p>Here is a simplified code (I have all the CSS classes ready):</p>
  
  <pre><code>class Example extends React.Component {
    state = {
      transitionIn: false,
    };
  
    componentDidMount = () =&gt; {
      this.setState({ transitionIn: true })
    }
  
    render() {
      return (
        &lt;CSSTransition
          in={this.state.transitionIn}
          timeout={1000}
          className={'wordTransition'}
        &gt;
          &lt;div&gt;dksjfnsdkjnfj&lt;/div&gt;
        &lt;/CSSTransition&gt;
      );
    }
  }
  </code></pre>
  
  <p><a href="https://codesandbox.io/s/rj5046zxoo" rel="nofollow noreferrer">https://codesandbox.io/s/rj5046zxoo</a></p>