title: React.js Duplicate key and Unreachable code BUGS
body: <p><strong>Hi I'm learning React.js and I'm making a ChatApp right now. 
  Here is my bug and codes.</strong></p>
  
  <blockquote>
    <p>./src/App.js   Line 10:7:  Duplicate key 'currentUsername' 
    no-dupe-keys</p>
    
    <p>./src/components/ChatScreen.jsx  Line 35:5:  Unreachable code 
    no-unreachable</p>
    
    <p>Search for the keywords to learn more about each warning.To ignore,
    add // eslint-disable-next-line to the line before.</p>
  </blockquote>
  
  <pre><code>import React, { Component } from 'react'
  import Chatkit from '@pusher/chatkit-client'
  
  class ChatScreen extends Component{
    constructor(props) {
      super(props)
      this.state = {
        currentUser: {}
      }
    }
  
    componentDidMount() {
      const chatManager = new Chatkit.ChatManager({
        instanceLocator: 'v1:us1:1308c34d-00c3-4257-b1c3-647cf56fd5fa',
        userId: this.props.currentUsername,
        tokenProvider: new Chatkit.TokenProvider({
          url: 'http://localhost:3000/authenticate',
        }),
      })
  
      chatManager
        .connect()
        .then(currentUser =&gt; {
          this.setState({ currentUser })
        })
        .catch(error =&gt; console.error('error', error))
    }
  
    render() {
      return (
        &lt;div&gt;
  
        &lt;/div&gt;
      )
      const styles = {
        container: {
          height: '100vh',
          display: 'flex',
          flexDirection: 'column',
        },
        chatContainer: {
          display: 'flex',
          flex: 1,
        },
        whosOnlineListContainer: {
          width: '300px',
          flex: 'none',
          padding: 20,
          backgroundColor: '#2c303b',
          color: 'white',
        },
        chatListContainer: {
          padding: 20,
          width: '85%',
          display: 'flex',
          flexDirection: 'column',
        },
      }
  
      return (
        &lt;div style={styles.container}&gt;
          &lt;div style={styles.chatContainer}&gt;
            &lt;aside style={styles.whosOnlineListContainer}&gt;
              &lt;h2&gt;Who's online PLACEHOLDER&lt;/h2&gt;
            &lt;/aside&gt;
            &lt;section style={styles.chatListContainer}&gt;
              &lt;h2&gt;Chat PLACEHOLDER&lt;/h2&gt;
            &lt;/section&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      );
    }
  }
  
  
  export default ChatScreen;
  </code></pre>
  
  <p>Could you help me?</p>